Quintessence of Dental Technology 2018 0867157836, 9780867157833

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Editorial

MACHINE LEARNING:

Artificial Intelligence for Diagnosis and Treatment Planning One of the most complex tasks of any esthetic oral rehabilitation is the development of a treatment plan. Assembling all the data gathered from multiple sources—such as medical and dental history, patient’s chief complaint, radiographs, cone beam computed tomography (CBCT), casts, bite registrations, occlusal analysis, tooth shade analysis, just to name a few—and then interpreting the data, coming to a conclusion, and fabricating visually acceptable prototypes (virtual or not) for communication with the patient and restorative team is not a easy task. Although it is clear that the advances in digital technology in recent years have made a highly positive impact, information remains fragmented. The restorative team still needs to collect different pieces of information using digital and nondigital formats and combine them using different digital platforms or analog methods to prepare an appropriate treatment plan. Not to mention that there are so many variables involved in an oral rehabilitation that the process of establishing a final treatment plan itself is very stressful and intricate. Minimal errors in data gathering can lead to unpredictable outcomes, and the lack of predictability is one of the most challenging fears in dentistry. We urgently need digital tools that allow us to record, in an all-in-one single platform, patient data dynamically (lips at rest, teeth display during smile and exaggerated smile, occlusal excursions and movements), statically (intraoral scan, extraoral scan, digital dental shade analysis, and CBCT), and historically (medical and dental history). While many systems provide the opportunity to design smiles, plan restorations, determine implant placement, or evaluate underlying structures, most of the systems available still lack full integration. Furthermore, many digital platforms remain based in traditional dentistry, where teeth still need to cut in order for the software algorithms to design and propose an acceptable restoration. Ideally we need fully digital data sequencing, where all digitally recorded data would allow complete analysis and study of occlusion (including vertical dimension of occlusion), dental esthetics, tooth position, enamel and dentin thickness, edentulous space, root canal therapy, and gingival esthetics to create the ultimate virtual patient. With the assistance of this technology, the human brain would then design a successful treatment plan with a minimally invasive approach in mind and monitor its outcome over time in the same digital platform. As the machine stores more information, better decisions could be drawn. This technology is already available in other fields. In medicine, for instance, a surge of interest in machine learning has resulted in an array of successful data-driven applications, ranging from medical image processing and diagnosis of specific diseases, to the broader tasks of decision support and outcome prediction. Through an artificial neural network—which resembles a biologic brain in the sense that it learns by responding to the environment and stores the acquired knowledge for future decisions—digital technology could help to predict the success of a given treatment or suggest its limitations. Dentistry could truly benefit from artificial intelligence and artificial neural networks, or at minimum all-in-one digital platforms offered at a reasonable cost. Digital workflow is clearly the theme of this year’s Quintessence of Dental Technology, with its collection of essays and cases demonstrating a combination of human ingenuity, artistry, and technology to promote better and high-quality dentistry. I welcome you to take the time to explore the possibilities shown in this book, to be curious, and to crave for knowledge with the excitement of all new possibilities.

Sillas Duarte, Jr, DDS, MS, PhD [email protected] © 2018 BY QUINTESSENCE PUBLISHING CO, INC. PRINTING OF THIS DOCUMENT IS RESTRICTED TO PERSONAL USE ONLY. NO PART MAY BE REPRODUCED OR TRANSMITTED IN ANY FORM WITHOUT WRITTEN PERMISSION FROM THE PUBLISHER.

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Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry

Masayuki Okawa, DDS1 Shigeo Kataoka, CDT2 Takahiro Aoki, CDT2 Koichi Yamamoto, DDS3

Private Practice, Daikanyama Address Dental Clinic, Tokyo, Japan. 2 Osaka Ceramic Training Center, Osaka, Japan. 3 Private Practice, Yamamoto Dental Clinic, Osaka, Japan. 1

Correspondence to: Dr Masayuki Okawa, Daikanyama Address Dental Clinic, 17-1-301 Daikanyama-cho, Shibuya-ku, Tokyo 150-0034, Japan. Email: [email protected]

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T

he minimally invasive intervention concept has become a standard prosthodontic treatment—a shift from the old standard concept of “retention and resistance.” The goal of prosthodontic treatment should be biomimetics and bioemulation, which lead to the minimally invasive concept by incorporating the current evolution of adhesive dentistry with further understanding of the biomechanics of tooth structure.1 Since Magne and Belser introduced various anterior bonded porcelain restoration cases in 2002,2 many clinicians, including the author, have been publishing welldocumented successful results for anterior teeth.3,4 Magne et al5,6 and Dietschi and Argente7 later published direct and indirect adhesive restorative techniques with the minimally invasive concept for posterior teeth. Since then, Duarte et al,8 Fradeani et al,9 Vailati et al,10 Okawa,11 and other clinicians have published minimally invasive full-mouth rehabilitation cases.12 New clinical workflows and materials for minimally invasive restorations also continue to be introduced. Moreover, the author has presented clinically successful minimally invasive restorations fabricated using a microscope to avoid technical errors.13 Since the introduction of digital dentistry—the recent paradigm shift in dentistry—it is important to understand its application in the minimally invasive restoration workflow.14 In this article, several important aspects of executing minimally invasive restorations are discussed through the presentation of full-mouth minimally invasive restorations for a case of severely acid-worn dentition.

CLINICAL GOAL OF INDIRECT MINIMALLY INVASIVE TREATMENT As previously noted, the author has been having excellent case outcomes and prognoses by working under the microscope. In the patient shown in Figs 1 to 6, the fractured anterior teeth were treated under the microscope with bonded porcelain restorations. Marginal integrity was stable, with no sign of marginal porcelain chipping or discoloration 9 years posttreatment. The author did not have much exposure to digital dentistry at the time of treating this patient. However, with micro dentistry (treatment under the microscope), high accuracy can be obtained and prosthetic errors avoided, with

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no compromise on the standard of treatment. For digital dentistry, this philosophical concept should be the same: not allowing any compromise on treatment quality. The treatment approach for maintaining a high-quality outcome by efficiently combining prosthetic traditional workflow and digital workflow is presented in this article.

Clinical Questions/Concerns Regarding Minimally Invasive Full-Mouth Rehabilitation 1. Recently, cases of minimally invasive or noninvasive fullmouth rehabilitations of severely worn dentition (due to chemical erosion, occlusal abrasion,15 enamel dysplasia, etc) have been presented widely. Is tooth reduction necessary for those cases?16 If necessary, how much reduction is needed for different types of cases? What type of finish line is appropriate? 2. Polymer versus all-ceramics: What is required to obtain accuracy of fit of restorations using a digital workflow? What kind of material choice is appropriate for milling the restoration? Should material choice be different depending on the location of the restoration, ie, anterior or posterior? 3. The provisional stage is extremely important for fullmouth rehabilitation cases in order to evaluate function and esthetics. Since adhesive restoration preparation does not require retention and resistance form, how can we choose the provisional restoration material? How do we cement the provisional restoration? What kind of temporary cement can be used?

RESTORATIVE TREATMENT FOR SEVERELY WORN DENTITION Severely worn dentition can be caused by acid erosion, parafunctional habits such as bruxism, malocclusion, or a combination of these. Severely worn dentition can cause esthetic, functional, and biologic issues, and this can lead to complete bite collapse. Restorative treatment is important to prevent further deterioration.17 Adhesive restoration to preserve the remaining tooth structure should be the treatment of choice in such cases.18

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Fig 1 Preoperative photograph of patient with four fractured maxillary anterior teeth. Fig 2 Teeth preparation. Fig 3 After completion of restorative treatment under microscope. Fig 4 Three-year postoperative radiographs. There is no detectable gap between the teeth and restoration margins even though radiopaque resin cement was used. 4

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Figs 5a and 5b Nine-year postoperative photographs. There is no discoloration on the anterior restoration supragingival margins. Fig 6 Magnification of supragingival margin under the microscope. No significant clinical negative changes can be observed 9 years postoperatively.

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CASE PRESENTATION Chief Complaints The patient, a 21-year-old fashion model, was concerned with the esthetics of her thin and short central incisors.

She also complained of sensitivity in the anterior teeth and muscle pain caused by her clenching habit. A later interview revealed that she had an eating disorder (bulimia). The patient wanted treatment to improve the anterior esthetics and posterior occlusion as well as eliminate teeth sensitivity.

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Figs 7a to 7c Clinical evaluation of facial esthetics and face-to-tooth relationships. The incisal edge position of the maxillary anterior teeth is shorter than the lower lip smile line, and the mandibular anterior teeth are slightly extruded. Those are the major esthetic issues.

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Initial Clinical Work-up Analysis of facial features and lip and teeth relationship.

The incisal edge position was concave and did not match the smile line. The mandibular anterior teeth were slightly extruded (Figs 7a to 7c). Intraoral photograph analysis. Figures 8a to 8c show the

anterior teeth in occlusion, anterior rest position, and anterior protrusive movement. There was no significant concern in terms of the maxillary cervical gingival levels, but the occlusal plane was canted to the right. The midline of the maxillary central incisors matched the facial midline. The midline of the mandibular central incisors was shifted to the right; therefore, the left canine relationship was Class III. The path of teeth guidance can be analyzed by examining the anterior teeth working contacts and wear pattern. This case was diagnosed as pathway to end-toend wear. Spear noted that overjet should be deeper and overbite shallower for cases such as this, with teeth contacts in functional movement until the end of the mandibular envelope movement.19 The four maxillary incisors appeared very thin (Figs 9a and 9b). All six maxillary anterior teeth showed incisal chip-

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ping and significant wear, so those teeth appeared to be very short. There was no decay or restorations on these teeth. The occlusal view (Fig 9b) shows the typical acid enamel erosion pattern and shiny worn-down occlusal surfaces.17 This wear pattern confirmed that acid erosion caused the dentin exposure, and the mandibular anterior labial incline and bruxism caused additional wear of the maxillary anterior teeth. Study model analysis. The acid erosion and occlusal wear

of the palatal surfaces of the maxillary anterior teeth could be seen on the initial study models (Figs 10a to 10d). Hard tissue defects caused by the acid erosion and occlusal wear were more prominent on the anterior teeth than the posterior teeth. The maxillary left first molar seemed to have been lost much earlier and left unrestored. The second and third molars were tilted mesially and closed the space of the first molar. The maxillary molars showed significant wear on the functional cusps, and the mandibular molars showed occlusal concavities, corresponding with the patient’s complaint of right molar clenching. There also was pain on palpation of the posterior belly of the digastric muscle. This implies that the right condyle could locate on the more posterior position.

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Figs 8a to 8c Initial preoperative photographs. Figs 9a and 9b Initial preoperative facial and occlusal views of the maxillary anterior teeth. Figs 10a to 10d Evaluation of initial preoperative study casts. (a) Maxillary anterior teeth, palatal view; (b) maxillary teeth, entire occlusal view; (c) maxillary right first and second molars, occlusal view; (d) mandibular right first and second molars, occlusal view.

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Fig 11 Preoperative full-mouth radiographs. Fig 12 Anatomy of thick enamel structure of anterior tooth’s lingual and interproximal areas. It is important to preserve those structures for tooth flexure control.

Radiographic analysis. All teeth were vital (Fig 11). Dental

decay was found on the interproximal surfaces of the mandibular right first and second molars. There were no periodontal concerns. The maxillary left second molar was mesially tilted.

Restorative Treatment Objectives and Treatment Planning An organized and sequenced treatment plan was established along with eliminating the risk factors of the acid erosion.17 The treatment plan objectives for patients with acid erosion should be to recover proper anatomical features; reestablish proper occlusion and function; improve esthetics, such as the smile line; and eliminate teeth sensitivity.11 This particular patient had more significant anterior

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teeth wear compared to posterior wear. Since the anterior teeth were already labially inclined, the ideal treatment choice preferably included either orthodontic intrusion or crown lengthening to create space for the future restorations rather than opening the vertical dimension of occlusion (VDO), in order not to create too much postoperative anterior teeth display. Orthodontic treatment,20 including uprighting the maxillary left second molar, was discussed with the patient. However, due to her occupational commitment, she could not undertake the suggested orthodontic treatment. Therefore, full-mouth rehabilitation with opening of the VDO became the final treatment plan. A predictable treatment outcome with opening of the VDO has been shown by Abduo.21 Spear stated that the ideal VDO21,22 does not exist; VDO can change and adapt to the patient’s condition, so an appropriate VDO for each individual patient needs to be determined.20 The restor-

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Fig 13 Two sets of study casts were mounted on the articulator by using the same centric relation registration. One set was for fabrication of the diagnostic wax-up and the other for fabrication of the provisional restorations and anterior guidance index. Fig 14 Esthetic evaluation and wax-up of the maxillary central incisors according to the patient’s request. Ideal incisal position was created by adding wax after evaluating the central incisors and upper lip position during a smile. General length, width, and tooth proportions were also taken into consideration. Patients with acid erosion tend to get used to the appearance of short teeth and usually do not request long teeth.23 Fig 15 Establishing the ideal occlusal plane according to proper occlusal plane concepts and esthetic requirements. In this case, the ideal occlusal plane was created by correcting the mesially tilted maxillary left first molar alignment. Fig 16 Palatal surfaces of the anterior teeth were recontoured in the wax-up. The maxillary left molars were also waxed and idealized.

ative treatment should bring back anatomy of the individual tooth by increasing VDO and then restore function and esthetics by preserving as much of the remaining tooth structure (Fig 12).

Workflow of Minimally Invasive Full-Mouth Rehabilitation The method to determine the ideal VDO for this patient was to fabricate a diagnostic wax-up on the articulator. The inter-

occlusal record was acquired and mounted on the articulator. Esthetic and functional requirements were evaluated in this order: maxillary central incisors, lateral incisors and canines, maxillary premolars and molars, mandibular anterior teeth, mandibular premolars and molars. The diagnostic wax-up should exhibit the ideal treatment plan goal visually. Meeting the patient’s esthetic demands and the operator’s functional goal should be the most important determinants of a new VDO. Figures 13 to 21 demonstrate the mounting of casts on the articulator, the diagnostic wax-up technique, and determination of the new VDO.

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Fig 17 Ideal protrusive movement path provided on the articulator. With the pathway to end-to-end wear in this case, overjet should be created deep and overbite shallow.19 Fig 18 New established VDO appreciated by closing the articulator. Fig 19 Mandibular movement paths defined by recontouring the maxillary anterior lingual surface wax.

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Figs 20a and 20b Ideal maximum intercuspation and nonworking-side molar disclusion were acquired by changing the mandibular molar shape within the wax-up. Figs 21a and 21b Mandibular right molars were mainly recontoured in the wax-up according to the idealized maxillary occlusal plane, thereby establishing the ideal occlusal plane.

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www.pdflobby.com Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry Figs 22a and 22b Preoperative study casts and diagnostic wax-up models were scanned using a tabletop scanner and the images then superimposed. Figs 23a and 23b Superimposed images. There is adequate space on the buccal, incisal, and palatal areas of the maxillary anterior teeth. Figs 24a and 24b The palatal veneer restorations for the maxillary anterior teeth and occlusal overlay restorations for the maxillary left molars were digitally created with the software after scanning of the preoperative study casts.

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The traditional approach for opening the VDO by using a familiar articulator to mount the master casts and completing diagnostic wax-up was selected for this treatment. However, after this step, digital dentistry was implemented. The microscope was used for restorative steps, such as teeth preparations, in order to minimize technical errors. Following are the five main treatment steps for this patient.

Step 1: Full-Mouth Provisional Restorations (Digital Approach) As shown in Figs 22 to 36, the full-mouth provisional restorations for this patient were fabricated digitally using the noninvasive approach, as was the goal. This case was categorized as Class IV according to the ACE analysis by Vailati and Belser.18 The author selected

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the sandwich veneer technique, with separate buccal and palatal veneers, for the six maxillary anterior teeth to preserve interproximal sound tooth structure, which has an important role in controlling the tooth flexure in teeth that have lost significant hard tissue due to acid erosion and occlusal wear. Anterior provisional restorations were cemented with provisional resin cement (Telio CS Link, Ivoclar Vivadent) by applying spot acid etch and bond. Posterior overlay provisional restorations do not have traditional “retention and resistance” form and yet receive heavy vertical and lateral occlusal loads, so regular provisional resin cement would not hold those restorations for long. Therefore, the inner surfaces of the posterior overlay provisional restorations were treated with primer (HC primer, Shofu), and non–self-adhesive resin cement (HC cement, Shofu) was used (Figs 32a and 32b).

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www.pdflobby.com OKAWA ET AL Fig 25a Palatal veneer restorations were milled from the PMMA disk. Fig 25b 3D image acquired by scanning the maxillary cast with palatal veneer restorations.

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Figs 26a and 26b Labial provisional veneer restorations for the maxillary anterior teeth were digitally created.

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Fig 27a Maxillary anterior labial veneer provisional restorations milled from PMMA disk. Fig 27b Maxillary labial and palatal provisional veneer restorations polished and ready for insertion. Figs 28a and 28b Fabricated sandwich veneer provisional restorations tried on the stone master casts.

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www.pdflobby.com Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry Figs 29a and 29b Posterior provisional overlay veneer restorations (a) designed and (b) fabricated. The VDO was not raised much in this case, so the posterior overlay provisional restorations were thin. These restorations were splinted in order to avoid stability issues during the provisional phase. Figs 30a and 30b Provisional restorations for the mandibular molars were fabricated using the direct bonding technique using a clear silicone matrix (Reveal, Bisco) since there was not enough clearance to fabricate PMMA provisional restorations with the noninvasive approach. Direct bonding was applied on the mandibular right first and second molars and first premolar and on the left first molar and second premolar.

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Figs 31a to 31c After setting preoperative casts with the new VDO on the articulator, an anterior index was fabricated to keep posterior interocclusal space with the new VDO during fabrication of the provisional restorations. The index is used to transfer the provisionals from the articulator to the patient’s mouth. It acts as an intraoral vertical stop. After inserting posterior provisional restorations with the index, the anterior sandwich technique provisional veneer restorations were inserted and anterior stop and guidance created. Figs 32a and 32b After the maxillary left molar overlay PMMA provisional restorations were placed using the anterior index, the direct composite provisional restorations for the mandibular right molars were placed.7 This created a new posterior vertical stop.

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www.pdflobby.com OKAWA ET AL Figs 33a and 33b Maxillary sandwich veneer provisional restoration insertion was performed under the microscope. It was difficult to insert these provisional restorations on the unprepared labial side because of the convex surface. Also inserting palatal provisional restorations at the same time on the same tooth can be challenging to perform without error. 33b

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Figs 34a and 34b Working under the microscope is extremely useful for insertion of palatal provisional veneer restorations on the unprepared tooth surface because it is concave.

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Fig 35 Provisional restorations fabricated for the noninvasive full-mouth rehabilitation.

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Figs 36a and 36b Final restoration casts created from the duplicated provisional restoration casts with some minor waxing and recontouring after the intraoral adjustments. After adjustment of the casts, both arches were scanned for the digital wax-up of the final restorations.

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Fig 37 After preparation of the mandibular right first and second molars. A great deal of occlusal wear was noted on the provisional restorations; interproximal decay was also detected. Therefore, those teeth needed to be prepared for lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) final restorations. Fig 38 Measuring the material thickness of the final restoration is an important step. With digital dentistry, this task is performed easily. After tooth preparation, prepared teeth and the entire arch are scanned by the intraoral scanner (Trios 3, 3Shape) and final restorations designed by digitally superimposing the scans with the software.

When occlusal rehabilitation treatment for heavy bruxists is carried out with altered VDO, there is a tendency for muscle activity to become more active 2 to 3 months into the treatment and for the patient to begin to break down the provisional restorations.24,25 In this patient, accordingly, there was chipping and wear of the provisional direct composite restorations on the mandibular right molars. The right condyle was also deviated forward after opening the VDO. This gave the assumption that the condyle was deviated posteriorly due to too much compressive stress. After several anterior and posterior occlusal adjustments, the patient became accustomed to the altered VDO and occlusion. The frequency of mandibular right-side provisional restoration repair was reduced and palpation pain in the posterior belly of the digastric muscle disappeared. Facially, the patient noticed less muscle bulk on the mandibular angle and she did not clench as much as previously. After these positive outcomes with the provisional restorations, it was decided to proceed to the final restorations. But first, impressions of both arches were taken for the digital wax-up of the final restorations, and the casts were refined using a curving and waxing technique.

Step 2: Molar Teeth Preparation (Microscope Technique) The full-mouth provisional restoration was accomplished with the completely noninvasive approach. However, be-

cause the direct composite provisional restorations on the mandibular right first and second molars were constantly chipping and wearing due to the patient’s strong bruxism, milled lithium disilicate (IPS e.max, Ivoclar Vivadent) was selected as the material of choice for the final restorations given its high strength and capability for etch and bond. This material will prevent the future loss of VDO and nonideal posterior rotation of the TMJ. The author has been using lithium disilicate clinically for minimally invasive molar restorations below the manufacturer’s recommended thickness (thinner than 0.8 mm); however, chipping or shear fracture has been occurring in patients with heavy bruxism. The author also believes that the press technique is an effective fabrication method for those extremely thin molar occlusal veneer restorations. For this case, preparation of the first and second molars was done to provide 0.8 to 1.00 mm thickness for the ceramic restorations.9 However, the preparation was kept in the enamel since interocclusal space was automatically created by increasing the VDO. Final preparations of the maxillary left first and second molars were done by preparing the PMMA provisional restorations under the microscope, and the final preparations of the mandibular first and second molars were done by preparing a direct composite resin mock-up under the microscope.26 The direct composite bonded restorations on the mandibular right and left second premolars and left first molar were in great condition; therefore, it was decided they would be the final restorations (Figs 37 to 40).

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Figs 39a and 39b Mandibular right first and second molar PMMA provisional restorations: (a) intraoral view and (b) preinsertion views of the four PMMA provisional restorations. The mandibular right first and second molar restorations were splinted for retention and had a holding notch applied on the individual restorations for easy removal. These PMMA restorations had great fit; however, possible material distortion during milling could occur because the restorations are very thin. Cementation was done with HC cement. Figs 40a and 40b Digital image of final restoration wax-up cast (provisional restorations modified casts) and digital image of prepared teeth are double scanned.

Step 3: Fabrication and Insertion of Posterior Final Restorations (Digital Approach) The posterior final restorations were fabricated digitally using IPS e.max CAD HT A1 block. e.max CAD was chosen as the restorative material for this case due to its wear re-

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sistance and esthetics. e.max CAD ceramic block can be milled as thin as 0.3 mm with the use of a new milling bur and setting milling time longer, although there are some small variations in results. It is rather easy to mill e.max CAD ceramic block since it is milled in the green stage. If the margin needs to be as thin as 0.2 to 0.3 mm, it should be milled thicker and then adjusted on the 3D-printed die model (Figs 41 to 43).

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www.pdflobby.com Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry Figs 41a to 41d (a) 3D-printed model is required for adjustment of occlusion, surface texturing, staining, margin adjustment, and polishing. IPS e.max CAD HT A1 block (a, b) before crystallization and (c) after crystallization. (d) Abutment dies produced by 3D printer and completed ceramic overlay restorations after staining. Fig 42a Lava Ultimate HT A1 block (3M ESPE), which is a polymer block, was milled under the same setting experimentally. It was milled as thin as 0.3 mm without problem. However, e.max CAD presented better light transmittance in the same HT A1 block. Fig 42b Try-in of Lava Ultimate overlay restorations. The stability and fit of the overlay restorations from the polymer block was satisfactory.

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Figs 43a and 43b IPS e.max CAD ceramic overlay restorations inserted on the mandibular right first and second molars. Rubber dam should be used for the bonding procedure to control moisture. Highly filled composite resin (ENA HRi, Micerium) was softened by heat and used as the bonding material due to its high bond strength and hardness. The ceramic overlay restorations on molars fabricated digitally were as accurate and esthetic as those using the traditional approach.

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Sandwich approach ACE Class IV Facial Ceramic Palatal Ceramic

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Fig 44 Data from the wax-up model of final restorations, which was refined from the provisional model and the data before abutment preparation, were superimposed to simulate the final restorations. The sandwich veneer technique was employed for the maxillary anterior teeth to preserve enamel in the proximal area, which is important for tooth flexure control. Figs 45a and 45b Cervical area was prepared 0.2 mm under the microscope. Fig 46 After completion of abutment preparation. Figs 47a and 47b Shape of prepared abutments and acquired material space was measured on the software.

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www.pdflobby.com Minimally Invasive Full-Mouth Rehabilitation Adapting Digital Dentistry Figs 48a and 48b Intraoral scan data from Trios 3 (3Shape).

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Step 4: Abutment Preparation of Anterior Teeth (Under Microscope) Sandwich veneer restoration was chosen for the maxillary anterior teeth. Non-preparation provisional restoration was possible because enough material space was secured at the time of diagnostic wax-up. When evaluating the provisionals, it was found that the restorations tended to slip away during the seating procedure due to the labial convex surface. A 0.2-mm feather-edge chamfer finish line was placed at the gingival level of the labial cervical area. Hence, the bonding procedure could be performed with control and the seating position checked under the microscope. This subtle tooth reduction should not affect the deflection of the tooth. Preparation of the incisal edge and lingual aspect involved only rounding the sharp edges. A microscope is required to perform minimal preparation accurately. And for the intraoral digital scanning, not limited to subgingival but for the veneer restorations, it is difficult to scan the tooth surfaces at adjacent contact points, so stripping reduction of the contact points should be done within the tolerance to avoid violating tooth flex-

ure. Labial veneers of maxillary anterior teeth can be thin as long as abutment flexure is minimum and bonding is in enamel without complications such as chipping or fracture. Many anterior teeth can be restored without any abutment preparation. Consideration of strength and direction of occlusal force and required material space is more critical in posterior teeth restoration (Figs 44 to 47).

Step 5: Fabrication and Insertion of Anterior Restorations (Digital and Traditional Approaches) Two sets of restorations were fabricated by two dental technicians using two different fabrication approaches for study purposes to compare the workflows and the results. The digitally fabricated restorations were designed using the digital data obtained by an intraoral scanner. After milling, they were stained and final adjustments were made on the model generated by the 3D printer (Figs 48 to 58). The second set of restorations used a combination of traditional and digital approaches. Labial veneers were fabricated

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www.pdflobby.com OKAWA ET AL

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Fig 49 Palatal veneers were first designed after superimposing the data from the provisional modified cast wax-up for final restorations and the data from intraoral scanning after abutment preparation. Fig 50 Milled palatal veneer restorations using IPS e.max CAD block according to the design shown in Fig 49. Figs 51a and 51b Palatal veneer restorations were tried on the 3D-printed model after crystallization and staining. Once fit was confirmed, scanning with a desktop scanner was carried out with the palatal veneer restorations seated on the 3D-printed model. Fig 52 Maxillary anterior labial veneers were designed on the superimposed data of the wax-up model of final restorations and scanned data of the 3D-printed model with palatal veneers seated. Individual dies were fabricated by sectioning the 3D-printed model and superimposed on the image to reproduce accurate veneer margins of the proximal area. Fig 53 Milled labial veneers using e.max CAD block from the data of Fig 52.

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Figs 54a and 54b Surface texture was given to the anterior veneers on the 3D-printed model before crystallization. The accuracy of milling in digital dentistry is sufficient. On the other hand, procedures such as above cannot be achieved digitally. In addition, sprue removal also makes manual work required. Fig 55 Completed anterior labial veneer restorations after crystallization and staining. Figs 56a and 56b Maxillary anterior sandwich veneer restorations completed using the digital approach (technician: Mr Takahiro Aoki, Osaka Ceramic Training Center). Fig 57 Try-in of sandwich veneer restorations. Natural shade and esthetics were achieved using the digital approach. Fig 58 Highly accurate marginal fit was achieved using the digital approach. Gingival margins cannot be distinguished by visually comparing the veneers before and after try-in.

QDT 2018 25

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www.pdflobby.com OKAWA ET AL Figs 59a and 59b Lingual sandwich veneer restorations were fabricated digitally on the stone model, and labial veneer restorations were fabricated traditionally. Silicone rubber impression and the master stone models are shown.

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Figs 60a to 60c Palatal veneer restorations were designed after superimposing of the data from the wax-up model for final restorations and the scan data of the stone master model after abutment preparation. Maxillary anterior palatal veneer restorations were milled out of IPS e.max CAD, crystallized, and then stained on the stone master model. Fig 61 Labial veneer restorations were fabricated using the porcelain layering technique on the refractory die (technician: Mr Shigeo Kataoka, Osaka Ceramic Training Center). Despite the progress in materials for digital fabrication, such as gradation monolithic block and staining technique, limitations in detailed coloring and light transmittance remain. The shape of mamelons, incisal halos, and creation of internal structure such as fluorescence still require the creative hand of the master technician, which will not change in the near future.

on a refractory cast using feldspathic porcelain and finished on the stone master model obtained by silicone impression. The stone master model was scanned and palatal

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veneers were designed digitally. They were milled, stained, and finished on the master model (Figs 59 to 64).

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Fig 62 Completed labial veneer restorations using refractory model technique. Surface texture was finished by the master ceramist. Fig 63 Completed sandwich veneer restorations using the traditional and digital approaches. Fig 64 Fit of labial veneer and palatal veneer restorations is confirmed on the stone model.

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Digital approach

Traditional combined with digital approach

Fig 65 Comparison of two different sets of maxillary anterior veneer restorations fabricated using only the digital approach and the traditional with the digital approach.

Fig 66 The patient chose the restorations fabricated by Mr Kataoka using a combination of the traditional and digital approaches.

Superior accuracy of fit and esthetics were achieved in both restorations (Fig 65). The result of the digital approach was better than expected preoperatively after utilizing original techniques and technology. After discussion with both technicians, it was decided to have the patient choose which of the two to be inserted as the final restorations. The patient chose the restorations fabricated using the combination of traditional and digital approaches (Fig 66).

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However, the restorations fabricated using only the digital approach would have achieved the same treatment goal satisfactorily. The patient was happy with the result of the restorations both esthetically and functionally (Figs 67 to 72). Again, the same level of result would have been achieved with the restorations fabricated using only the digital approach.

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Fig 67 Natural esthetics was achieved even at the palatal junction area. Figs 68a to 68c Frontal and maxillary/mandibular occlusal views of the final minimally invasive full-mouth rehabilitation using the traditional and digital approaches.

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Fig 69 Postoperative full-mouth radiographs. It is evident that the maximum possible amount of tooth structure was preserved. Fig 70 Postoperative panoramic radiograph. The mandibular occlusal plane was well leveled by increasing VDO. Fig 71 With the treatment performed under enlarged view of the microscope,27 the cervical labial margin of the veneer restoration fabricated on the refractory model was so well fitted that it was undetectable even under microscopic view and achieved superior marginal blending with surrounding enamel.

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Fig 72 The patient’s new natural-looking smile and dramatically improved smile line.

CONCLUSION Digital technology can be applied to minimally invasive full-mouth rehabilitation because of factors such as supragingival margins, accurate intraoral scan data, and reproducibility of PMMA provisional restorations. The dentist and technician have to be somewhat creative and be able to acclimatize their steps and procedures, such as abutment preparation, veneer design, milling, and 3Dprinted model fabrication. Technical procedures such as creating particular surface textures, staining, adjustment of occlusion and margins are required and performed manually using a 3D-printed or CAD/CAM model.

It is clear that minimally invasive treatment will be the mainstream of restorative dentistry. The dentist and the technician need to figure out how to utilize digital technology and incorporate it into the traditional workflow to maintain or improve treatment quality. Progress in digital software, milling machines, and materials will not stop. Master-quality work is still created by the hands of the clinician and technician, which will not change. Our patients’ satisfaction is achieved by adding a truly natural appearance to the artificial restoration.

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REFERENCES 1. Dietschi D, Spreafico R. Evidence-based concepts and procedures for bonded inlays and onlays. Part 1. Historical perspectives and clinical rationale for a biosubstitutive approach. Eur J Esthet Dent 2015;10:210–227. 2. Magne P, Belser UC. Bonded Porcelain Restorations in the Anterior Dentition. Chicago: Quintessence, 2002:129–176. 3. Okawa M, Tsuchiya S. Team dynamics. Quintessence J Dent Technol 2008;6:1. 4. Okawa M, Yamamoto S. Exzellente dentale asthetik. Quintessenz Zahntech 2013;39:11–12. 5. Magne P, Knezevic A. Simulated fatigue resistance of composite resin versus porcelain CAD/CAM overlay restorations on endodontically treated molars. Quintessence Int 2009;40:125–133. 6. Magne P, Belser UC. Rationalization of shape and related stress distribution in posterior teeth: A finite element study using nonlinear contact analysis. Int J Periodontics Restorative Dent 2002;22:425– 433. 7. Dietschi D, Argente A. A comprehensive and conservative approach for the restoration of abrasion and erosion. Part II: Clinical procedures and case report. Eur J Esthet Dent 2011;6:142–159. 8. Duarte S, Sartori N, Cascione D, Phark JH. Ceramic-reinforced polymers: Overview of CAD/CAM hybrid restorative materials. Quintessence Dent Technol 2014;27:32–48. 9. Fradeani M, Barducci G, Bacherini L, Brennan M. Esthetic rehabilitation of a severely worn dentition with minimally invasive prosthetic procedures (MIPP). Int J Periodontics Restorative Dent 2012;32: 135–147. 10. Vailati F, Brugera A, Belser U. Minimally invasive treatment of initial dental erosion using pressed lithium disilicate glass-ceramic restorations: A case report. Quintessence Dent Technol 2012;35:65–78. 11. Okawa M. Minimally invasive full-mouth rehabilitation for dental erosion. Quintessence Dent Technol 2016;39:57–77. 12. Duarte S. Sartori N. Biomaterials update: The adhesive restorative complex (ARC) Concept. Quintessence Dent Technol 2017;40:48– 65. 13. Okawa M. Efficacy of working under a microscope for bonded porcelain restorations [in Japanese]. Quintessence Microdentistry Yearbook 2011. Tokyo: Quintessence, 2011:66–78.

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14. Cofar F, Cofar I, Sttumpf L. RAW: A digital workflow. Quintessence Dent Technol 2017;40:6–25. 15. Gerdolle D, Mortier E, Richard A. Full-mouth adhesive rehabilitation in a case of amelogenesis imperfecta: A 5-year follow-up case report. Eur J Esthet Dent 2015;10:12–31. 16. Scopin O, Borges G, Kyrillos M. The area of adhesive continuity: A new concept for bonded ceramic restorations. Quintessence Dent Technol 2013;36:9–26. 17. Dietschi D, Argente A. A comprehensive and conservative approach for the restoration of abrasion and erosion. Part I: Concepts and clinical rationale for early intervention using adhesive techniques. Eur J Esthet Dent 2011;6:20–33. 18. Vailati F, Belser UC. Classification and treatment of the anterior maxillary dentition affected by dental erosion: The ACE classification. Int J Periodontics Restorative Dent 2010;30:559–571. 19. Spear F. Facially Generated Treatment Planning. Scottsdale: Spear Education, 2005. 20. Spear F, Kinzer G. Approach to vertical dimension. In: Cohen M (ed). Interdisciplinary Treatment Planning: Principles, Design, Implementation. Berlin: Quintessence, 2010:213–246. 21. Abduo J. Safety of increasing vertical dimension of occlusion: A systematic review. Quintessence Int 2012;43:369–380. 22. Walther W. Determinants of a healthy aging dentition: Maximum number of bilateral centric stops and optimum vertical dimension of occlusion. Int J Prosthodont 2003;16(suppl):77–79. 23. Vailati F, Carciofo S. Treatment planning of adhesive additive rehabilitations: The progressive wax-up of the three-step technique. Int J Esthet Dent 2016;11:356–377. 24. Maxwell LC, Carlson DS, McNamara JA Jr, Faulkner JA. Adaptation of the masseter and temporalis muscles following alteration in length with or without surgical detachment. Anat Rec 1981;200:127–137. 25. Helsing G. Functional adaptation to change in vertical dimension. J Prosthet Dent 1984;52:867–870. 26. Bacherini L, Brennan M, Bocabella L, Vigiani P. Esthetic rehabilitation of a severely discolored dentition with minimally invasive prosthetic procedures (MIPP). Quintessence Dent Technol 2013;36:59–76. 27. Massironi D, Pascetta R, Romeo G. Precision in Dental Esthetics: Clinical and Laboratory Procedures. Milan: Quintessenza Edizioni, 2006:126–141.

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The Slim Concept—

Iñaki Gamborena, DMD, MSD, FID1 Yoshihiro Sasaki, CDT2 Markus B. Blatz, DMD, PhD3

Adjunct Professor, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania, USA, and Private Practice, San Sebastián, Spain. 2 Shinbi Laboratory, San Sebastián, Spain. 3 Professor of Restorative Dentistry and Chairman, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania, USA. 1

Correspondence to: Dr Iñaki Gamborena, C/ resurrección M Azkue #6 -4, 20018 San Sebastián, Guipúzcoa, Spain. Email: [email protected], www.Drgamborena.com

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Clinical Steps to Ultimate Success

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s described in the authors’ previous article published in QDT 2017, the Slim concept provides the unique ability to create an abundance of soft tissue volume in the early surgical stages of implant restoration. It involves protocols and components, the Slim heal-

ing abutment being the most important, that enable long-term esthetic and functional success. The following case details further the clinical steps of the Slim concept in a patient ideally restored with implant crown restorations along with veneers in the anterior maxilla.

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CASE PRESENTATION A female patient presented with a removable partial denture replacing the maxillary right central and lateral incisors and first premolar as well as the maxillary left premolars (Fig 1). Her request was to have implantsupported fixed dental prostheses replace those teeth. The panoramic radiograph and cone beam computed tomography (CBCT) scan revealed the magnitude of the bone loss, especially on the buccal aspect, when compared to the adjacent central and lateral incisors (Fig 2). The heights of the papillae on the mesial and distal aspects of the defect were almost ideal, except for the volume loss on the buccal aspect (Fig 3). The large buccal and vertical defect in the edentulous area was caused by excessive pressure from the base of the removable denture, which replaced the teeth extracted about 10 years earlier.

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Graft, Implant, and Slim Placement (Figs 4 to 9) CBCT examination of maxillary tuberosities indicated sufficient soft tissue thickness to serve as preferred donor sites for subepithelial connective tissue grafts. Connective tissue from the tuber areas is more dense and provides better long-term stability than palatal tissue; however, it requires complete coverage to ensure adequate vascularization and avoid necrotizing. Since bone augmentation procedures add another level of complexity and unpredictability, it was decided to augment the deficient sites solely with a connective tissue graft. A buccal and crestal incision was made on the edentulous ridge, and a partial-thickness flap was elevated to increase the volume and tissue height, especially between the implants and buccolingually. A sulcular incision was

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made around the mesial and distal aspects of the teeth, and the papillae adjacent to the defect were elevated. Finally, the partial-thickness flap was prepared and raised above the mucogingival junction (MGJ) until it reached the desired coronal position. No vertical releasing incisions were made and the periosteum was left on the bone. A NobelActive NP 3.5 × 13-mm implant (NobelBiocare) was placed in the area of the maxillary right central incisor and a NobelActive 3.0 × 13-mm implant in the area of the lateral incisor. Slim healing abutments with 7-mm heights were selected to maximize crestal tissue grafting and enable primary flap closure. A large free tissue graft was harvested from the maxillary tuberosity and carefully deepithelialized. The connective tissue graft was sutured in position to the palatal aspect of the flap. The buccal flap was then sutured exactly to the initial incision to close the wound. Monofilament suture material (6-0 PTFE) was used to secure the tissues in place, and a 6-0 monopropylene suture was used for precise flap closure. This type of surgery should always be performed in one stage together with implant placement.

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Implant Planning and Execution (Fig 10) Bone morphology, implant selection, and surgical placement were assessed and determined with digital implant planning software. Virtual implant selection and placement suggested two NobelActive NP implants (3.5 × 13 mm). The yellow line indicates the bone level on the adjacent teeth and assists in the determination if bone or soft tissue augmentation is needed. About 3.7 mm of tissue depth for the central and 3 mm for the lateral incisor would be necessary to control tissue scallop and volume to mimic the adjacent site. Due to the thin buccal plate, the implant for the lateral incisor was selected to have a 3.0-mm diameter.

Healing Phase (Figs 11 to 13) The removable partial denture served as a provisional restoration and was adjusted to avoid any contact with the augmented site. The 3-month follow-up showed that the

QDT 2018 37

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original goal of creating a soft tissue contour similar to the adjacent site was achieved. The Slim healing abutments were initially completely covered with soft tissue, indicating the great volume gained.

Provisional Impression/Slim Management (Figs 14 to 17) Three months after surgery, an impression of the implants was made under local anesthesia. Removal of the healing abutments and connection of the impression copings were done carefully due to the large amount of tissue to displace, the bone depth, and the diameter of the impression copings—the smaller the better. Due to their wider base, Slim healing abutments must be removed with pliers. The impression coping was inserted with vertical pressure, and seating was verified radiographically. A diagnostic full-contour wax-up was made to replicate the natural tooth and duplicate its diameter, especially in the gingival third. A line was drawn on the master cast following the ideal scallop of the wax-up, and the desired emergence profile was carved from that line to the abutment head. Polyvinyl siloxane (PVS) matrices were made to visualize the full-contour wax-up and fabricate the composite abutment. The stone was carved with hand instruments until a divergent cone was created from the implant head. Composite abutments were then scanned and transformed in zirconia.

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Provisional Restoration/Adaptation (Figs 18 to 20) After the Slim abutments were removed with the patient under anesthesia, the final zirconia (Zr) abutments were connected and verified radiographically. Some interproximal bone had to be trimmed with diamond burs until final adaptation. No flap was deflected and all bone recontouring was done through the tissue hole created by the Zr abutments. The abutment screw of the 3.0 NobelActive implant should not be torqued beyond 15 Ncm. Ischemia is related to pressure and blanching of the tissues, which reduces blood supply and may cause necrosis of the surrounding tissues. The provisional crowns were then relined chairside to establish ideal fit and proper interproximal contact areas. The abutments were disconnected to adapt the margins and polish the provisional crown restorations extraorally.

Papilla Loss/Second Graft (Figs 21 to 25) During the healing process (3 months), papilla between the two implants was lost, which was likely caused by a loosening of the provisional and trauma due to incorrect occlusion. Buccal tissue volume was adequate. A second connective tissue graft was placed in the papilla area to improve the volume and density of the lost papilla. Zr abut-

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ments were modified to allow more space for grafting. A tunnel incision on the papilla and adjacent implants was prepared to attach the second connective tissue graft buc-

copalatally. A 6-0 PTFE monofilament suture material was used for that, while a 6-0 monopropylene suture was used for exact flap closure adaptation and positioning.

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Prosthetic Phase Healing (Figs 26 to 28) After 9 months, the healing process of the grafted site around the Zr abutments and provisional restorations was reevaluated. The soft tissue situation with respect to volume, interproximal height, and buccal/palatal support was almost ideal. Some additional pressure was needed on the buccal aspect to control and blend the scallop of the implant restoration with the adjacent central incisor. The original Zr abutments were replaced by an ASC (angulated screw channel) Zr abutment on the central and a new titanium/Zr abutment on the lateral incisor, due to fracture of the Zr abutment as seen on the periapical radiograph. A pick-up impression of the provisional restorations was made and poured in stone while the patient was waiting. This impression is helpful to transfer the emergence profiles but lacks accuracy in the interproximal contact areas.

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Veneers: Preparation/Final Impression (Figs 29 to 31) The maxillary left central and lateral incisors were prepared for porcelain laminate veneers to improve the overall esthetic outcome. The veneers were completed first and the veneered teeth would be used to match the implant crowns to their exact shade, value, and translucency. The preparation was approximately 1.4 mm in depth at the middle third of the tooth to create sufficient space for the ceramist to mask the dark shade of the natural abutment teeth. Since the interproximal contact areas were not completely opened, clear matrices were placed to facilitate sectioning of the individual dies in the laboratory during master cast fabrication. A two-cord technique was applied for the definitive impression, with a #000 retraction cord carefully placed into the sulcus first for margin location and to con-

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trol intracrevicular fluids and bleeding, and a #00 cord placed on top to further deflect the soft tissue and capture the finishing line. The top cord was removed immediately before the impression material was applied while the first cord stayed in the sulcus. Customized dies were fabricated for the prepared teeth with flowable composite. These dies were then stained chairside to replicate the shade of the natural abutment teeth as closely as possible. These customized dies allow dental technicians to adapt their porcelain layering technique individually and simulate the esthetic outcome in the laboratory.

Veneers: Model Work, Porcelain Buildup (Figs 32 to 35) A “Geller model” was made from the definitive impression to fabricate the two porcelain laminate veneers. The clear matrices in the interproximal areas allow the technician to trim the dies more efficiently and delicately without damaging the interproximal finish lines. The trimmed dies are placed back in the impression and secured into position to then pour the rest of the impression with stone, creating a master cast that allows the prepared dies to be removed while keeping the soft tissue contour of the model intact. During layering of the porcelain, the dental technician can simulate and verify the expected outcome on the customized composite dies in terms of final shade, value, chroma, and translucency.

QDT 2018 41

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Zr Abutment Fabrication (Figs 36 and 37) The new Zr abutments were fabricated to provide better support of the soft tissues after the second connective tissue graft. Modifications were also necessary to meet the goal of having the soft tissues supported 90% by the abutment and 10% by the crown. A two-piece Zr abutment was fabricated for the lateral incisor since there was no metal connection available for the specific implant (3.0 mm NobelActive). The Zr abutment part was bonded to a titanium abutment to maximize the esthetic outcome. It was first built in composite to the ideal contour. The composite and supporting titanium abutments were then scanned to design and fabricate the Zr component. The Zr abutment was perforated to facilitate the bonding process and limit voids in the resin cement.

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To block out the dark color of the titanium, three different resin cements were selected and tested with respect to their level of opacity. Of those, the high-opacity (Ho0) Multilink Hybrid abutment cement (Ivoclar Vivadent) seemed to provide the best ability to mask the titanium.

Abutment Scanning (Fig 38) The plastic ASC wax-up sleeve engaging abutment was connected to the laboratory analog, and composite resin was placed between the conically carved stone and the plastic sleeve until the ideal contour was achieved. The composite abutment was light cured and prepared to create a 1-mm subgingival margin on the buccal aspect of the ideally carved scallop and a slightly supragingival margin on the palatal aspect. The composite abutment was

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scanned (Nobel Biocare 2G scanner), allowing the technician to order a duplicate Zr abutment of the provisional abutment from the milling center.

Veneer Cementation and Final Impression (Figs 39 to 44) Impression copings were fabricated with an acrylic resin material on top of the final Zr abutments to ensure preci-

sion when pouring the impression in stone, to not disturb the soft tissues, and to speed up the process during the final impression of the maxilla after final cementation of the two porcelain laminate veneers. A double-cord technique was used for the two canines (first cord #3 and second cord #1) and multilayered single #1 cord around the Zr abutments on the premolar implants. The final Zr abutments were placed into the acrylic copings under the microscope before the impression was poured in stone.

QDT 2018 43

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45

46

47

48

49

Bisque Bake Try-in (Figs 45 to 47)

Delivery of Zr Crowns (Figs 48 and 49)

To assess the final value and shade, glycerin gel was painted on the intaglio surfaces of the crowns during bisque bake try-in. The shapes of the crowns were modified by adding composite; this would also give the dental technician some guidance for the finalization of the restorations. All functional and esthetic parameters were assessed and adjusted as needed. All crowns were cemented with provisional cement, and a pick-up impression was made to communicate the present soft tissue topography.

The soft tissue support was carefully evaluated on the pick-up model in terms of scallop, volume, interproximal contour, embrasure spaces, and contact areas. Additional pressure was exerted by the semi-pontic design on the buccal aspect of the implant crowns to blend the conventional with the implant-supported restorations.

44 QDT 2018

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www.pdflobby.com The Slim Concept—Clinical Steps to Ultimate Success

50

51

53

54

52

55

56

57

Try-in of Zr Crowns (Figs 50 to 55) The implant abutments were disinfected in 2% glutaraldehyde for 10 minutes and rinsed thoroughly before connecting them to the implants. The tissues were carefully inspected and any cement remnants from prior interventions were removed. The abutments were torqued to 35 Ncm on the maxillary right central incisor and 15 Ncm on the right lateral incisor, as recommended by the manufacturer. Periapical radiographs were taken to verify fit and proper seating of the components. All esthetic and function parameters were verified during the final try-in.

Cementation of Zr Crowns (Figs 56 and 57) For final cementation of the implant crowns, two retraction cords were placed independently: one on the buccal and the other on the palatal aspect of each abutment. The cords were extended into the sulcus of the adjacent teeth, which allows for easy retrieval of the cords and control of cement removal from both sides, buccally and palatally, in an independent manner. Self-adhesive cement (Rely X Unicem, 3M ESPE) was used for final cementation. A periapical radiograph was taken after cleaning of the cementation site with dental floss.

QDT 2018 45

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58

60

59 61

62

63

Final Result The preoperative compared to postoperative results (Figs 58 to 63) and 1-year postcementation situation (Figs 64 to 68) indicate a favorable blend of the various treatments performed in this patient—from conservative internal bleaching and direct composite restorations on the

46 QDT 2018

mandibular central incisors, to single-tooth implants with crestal connective tissue grafts to improve the soft tissue volumes, to porcelain laminate veneers, conventional crowns, and zirconia fixed dental prostheses. The high smile line demanded a carefully planned and executed approach to provide the patient with optimal and long-term stable prosthetic and soft tissue outcomes.

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65

64

66

67

68

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Copyright of Quintessence of Dental Technology (QDT) is the property of Quintessence Publishing Company Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

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B IOMATE R IALS & DIG ITAL TECH NOLOGY U PDATE

Assistant Professor and Assistant Director, Advanced Program in Operative & Adhesive Dentistry, Division of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 2 Resident, Advanced Program in Operative & Adhesive Dentistry, Master of Science Candidate in Craniofacial Biology, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 3 Assistant Professor, Advanced Orthodontics, Division of Endodontics, OMS, and Orthodontics, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 4 Associate Professor and Chair, Division of Restorative Sciences, Director of the Advanced Program in Operative Dentistry, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 1

Correspondence to: Dr Neimar Sartori, Division of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California, 925 W 34th Street, DEN 4365 Los Angeles, CA 90089-0641, USA. Email: [email protected]

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Digital Workflow for Multidisciplinary Esthetic and Functional Rehabilitation

Neimar Sartori, DDS, MS, PhD1 Sara Casado, DMD, MS2 Dan Grauer, DDS, MS, MOrth, PhD3 Sillas Duarte, Jr, DDS, MS, PhD4

D

igital technology is one of the fastest growing segments of dentistry. Computer-aided design/ computer-aided manufacturing (CAD/CAM) technology used to focus on the digital designing and fabrication of single or fixed partial denture restorations aiming to minimize chairside time, inaccuracy due to impression and cast distortion, and human error.1 Since the first dental

chairside CAD/CAM system was introduced in the mid1980s, there has been a considerable increase in both number of digital workflow CAD/CAM systems and range of indications.2 The main reasons for the fast development of CAD/CAM technologies are: (1) better, smaller, and faster intraoral scanners; (2) more user-friendly CAD design software; and (3) advancement in milling technology.2

QDT 2018

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49

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2

1

Fig 1 Preoperative facial view of patient showing vertical asymmetry of the mandible. Fig 2 Preoperative intraoral view. The patient was missing the maxillary right central incisor and mandibular first molar. Diagnosis included skeletal Class II, excessive overjet, open bite tendency, and deep curve of Spee, as well as unilateral posterior crossbite on the right side, retained deciduous maxillary canines, and mandibular midline deviated to the right.

One area that has significantly benefited from digital technology is orthodontics. Three-dimensional digital technologies have aided orthodontists in diagnosis, treatment planning of clear aligner therapies, custom facial and lingual orthodontic systems, and titanium Herbst appliances.3 As of late, orthodontists can also fabricate customized brackets, machine-milled indirect bonding jigs, and robotically generated archwires with patient-specific torque.4 The association of digital intraoral scanning and CBCT can be highly effective on multidisciplinary three-dimensional computer-assisted treatment (3DCAT) planning for esthetic and functional dental rehabilitation. The 3DCAT planning simplifies and improves communication among different dental professionals and with the patient by creating a treatment plan that can be easily visualized on the computer screen.5 A dental team composed of orthodontist, restorative dentist, and dental technician can virtually position and angulate teeth to the ideal location while providing the proper digital design of the restorations. The combined digital design is essential for a better understanding of benefits and limitations of the treatment, as well as to ensure the success of the future esthetic and functional rehabilitation. Patients can provide immediate feedback and possible modification even before esthetic and functional dental prototypes are created. Once the prototypes, based upon the digital design, are fabricated, it

50 QDT 2018

is possible to identify different aspects of the treatment before any restorative treatment is initiated.5,6 This article aims to provide an overview of the digital workflow possibilities for multidisciplinary esthetic and functional rehabilitations.

3D COMPUTER-ASSISTED TREATMENT FOR A DIGITAL WORKFLOW The interdisciplinary 3DCAT planning should start with a clear understanding of the patient’s chief complaints, clinical evaluation, and data collection. Two-dimensional (2D) digital records, such as extra- and intraoral photographs and videos (Figs 1 and 2) are highly recommended. Then 3D digital records, such as CBCT (Fig 3), intraoral scanning, and occlusal relationships must also be recorded to produce a 3DCAT planning. If orthodontic treatment is necessary, the dental team can use that information for the 2D and 3D records to virtually make the appropriate modifications on the patient’s teeth position and angulation through virtual orthodontic treatment. Insignia (Ormco) and Planmeca Romexis (Planmeca) are examples of design software that allow the virtual treatment planning method

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www.pdflobby.com Digital Workflow for Multidisciplinary Esthetic and Functional Rehabilitation Fig 3 Preoperative CBCT shows bone resorption and deficient ridge height and width at the maxillary right central incisor site. Impacted maxillary permanent canines are also observed. Figs 4a and 4b A virtual setup was created using Insignia (Ormco). The maxillary right lateral incisor was brought to the site of right central to regenerate alveolar bone in a lateral direction. The maxillary right permanent canine was exposed and brought to the arch through forced eruption to the lateral incisor site. The maxillary left first premolar replaced the extracted, and previously impacted, maxillary left canine. Crossbite was corrected by lateral expansion of the maxillary arch. Dental Class II relationship was corrected by retraction and extrusion of the maxillary incisors and canines. This extrusion increased the incisor exposure at rest and at smile.

3

4a

4b

(Fig 4).7 Once the patient accepts the treatment, the clinician can initiate the virtually guided orthodontic treatment. Once the orthodontic treatment is completed, new intraand extraoral photographs as well as intraoral scans are taken to reevaluate the patient’s postorthodontic esthetics and teeth length, proportion, contours, and display (Figs 5 and 6). The restorative digital esthetic design can be performed in 2D using presentation software such as Keynote (iWork, Apple) or Microsoft PowerPoint (Microsoft Office, Microsoft), independent standalone software for treatment planning (eg, Digital Smile Design), tablet applications (eg, GETApp, Fradeani Group Srl), or a 3D CAD/CAM chairside system (eg, Cerec Smile Design; Planmeca Romexis Smile Design, Planmeca).8–10 Evaluation of the teeth contours with the ideal widthlength ratio11 helps the restorative team to evaluate the risk factors of the case as well as to facilitate communication with the patient (Figs 7a and 7b).5 The digital treatment planning information performed with 2D software can be transferred to a 3D system using the “see-through” principle,12 which allows overlaying the design created in

2D onto the patient’s intraoral scanned dental arch to generate a reference for esthetic prototypes. Another option, if digital treatment planning software is available within a CAD program, is importing the patient’s portrait photography into the CAD software so esthetics is virtually designed using the patient’s face as a reference (Fig 8).8,10,12 The esthetic prototypes can then be milled in polymethyl methacrylate (PMMA) or resin-base materials, or 3D printed.10,12 After fabrication, intraoral evaluation of restoration prototypes allows dentist and patient to assess whether any modifications of restoration or tooth structure are necessary to achieve the desired function, esthetics, and phonetics (Fig 9). Once the restorative team receives the patient’s approval, the modified esthetic prototype is digitally scanned intraorally, so the modified prototype can be converted into the final restorations. CAD software tools, such as biogeneric copy (Cerec, Sirona Dentsply), preoperative (PlanCAD, Planmeca), or align and reuse (3Shape, Trios) are examples of these design functions within the CAD/CAM system.8,13

QDT 2018 51

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5

6

7a

7b

8

9

Fig 5 Postorthodontic preoperative view of the patient’s smile. Fig 6 Postorthodontic preoperative intraoral view of the patient showing teeth in an adequate position and angulation for the restorative treatment. Fig 7a Teeth outline showing the relationship between the preoperative situation and the ideal design. Fig 7b Occlusal view shows areas where facial and proximal reduction are needed. Fig 8 Patient portrait with the virtually designed restoration prototypes. Fig 9 Try-in of the restoration prototypes milled in PMMA.

52 QDT 2018

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www.pdflobby.com Digital Workflow for Multidisciplinary Esthetic and Functional Rehabilitation Figs 10a to 10c Facial tooth enameloplasty guided by the restoration prototype to avoid unnecessary removal of tooth structure. Fig 11 Final minimally invasive tooth recontouring. Areas of overcontour and undercuts were removed and teeth polished before optical impression. Figs 12a and 12b Restorations were designed based on restoration prototypes approved by the patient.

10b

10a

10c

11

12b

12a

CONSIDERATION FOR TOOTH PREPARATION Tooth Position, Angulation, and Shade Teeth with favorable dental shade, correct position, and angulation provided by the orthodontic treatment only require enamel-guided recontouring.14,15 The tooth recontouring should be performed based on (1) the possibility of increasing the volume on the teeth’s facial surface and (2) the need to create a path of insertion for the ultrathin bonded porcelain veneer.14,15 To ensure maximum enamel

preservation, tooth preparation must be guided by the restoration prototypes and reduction guides, and the gingival finishing line should be less than 0.3 mm of depth to avoid dentin exposure (Figs 10a and 10b).14,15 Before intraoral scanning, tooth preparations should be polished, because smooth surfaces ensure better scanning and superior internal fit of milled ceramic restorations. The better fit can be explained by the possibility to significantly reduce the internal spacer, and later, during bonding, the adhesive luting film thickness (Fig 11). Digital intraoral scanned 3D files can be used to design and fabricate the restorations (Figs 12a and 12b) using a

QDT 2018 53

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Table 1

Scanner

Software

Overview of the Most Common Chairside Systems on the Market Carestream Dental CS (3600 and Dental Wings CS 3500) DWIO

Dentsply Sirona (Cerec AC and Cerec Omnicam)

Fona Dental myCrown Scan

Powder

No

No

No

Yes

Color display

Yes

No

No

No (powderdependent)

Imaging mode

CS 3600: Video CS 3500: Single frame

Video

Video

Video

Imaging principle

Triangulation

Multiscan (10 cameras)

Triangulation

Stereo photogrammetry

Digital workflow

Chairside

Chairside

Chairside

Chairside

Data export

STL and PLY

STL

STL (model)

Not known

CAD/Design

CS Restore

DWOS Chairside

Cerec SW Cerec Premium SW

myCrown Design

CAM

CS Restore CS Connect as cloud for laboratory connection

DWOS Chairside

Cerec SW Cerec Premium CAM

myCrown Design

CS 3000

DW Lasermill— DWLM

Cerec MC (X/XL)

myCrown Mill

Axes

4 axes

6 independent axes Laser ablation

4 axes: 3+1-axis milling machine

4 axes: 3×2-axis stepper motor driver with microstepping

Materials

Zirconia, glassceramic, PMMA, composite, hybrid ceramic

Glass-ceramic, PMMA, composite, hybrid ceramic

Zirconia, glassceramic, PMMA, composite, hybrid ceramic (MCXL: CoCr)

Zirconia, glassceramic, PMMA, composite

Wet/dry processing

Wet

Dry

Wet & dry

Wet

Milling/grinding

Grinding

Laser pulses

Milling & grinding

Milling & grinding

Milling/CAM unit

Chairside systems information obtained from Zaruba and Mehl.2

chairside CAD/CAM system (Table 1).2 It is important that the intraoral scanner and milling unit are calibrated and the milling settings properly adjusted before milling ultrathin ceramic restorations. Otherwise, there might be chipping on the margins or perforation of the ceramic restorations.

54 QDT 2018

If the restorations will be fabricated by a dental laboratory, the dentist only needs to perform a digital impression using an intraoral scanner compatible with the CAD/CAM system used by the laboratory (Tables 1 and 2).2,16

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Planmeca (PlanScan and Emerald)

Zfx Zfx IntraScan

Ivoclar Vivadent/ 3Shape Trios 3

Lyra/ 3Shape Trios 3

Straumann/ 3Shape Trios 3; Straumann Cares intraoral scanner (Dental Wings DWIO)

No

No

No

No

No

Yes (grayscale optional)

No

Yes

Yes

Trios 3: Yes Trios 3 Mono: No

Video

Video

Video

Video

Video

Triangulation

Confocal laser technology

Confocal laser technology

Confocal laser technology

Confocal laser technology

Chairside

Chairside

Chairside cooperation

Chairside cooperation

Chairside cooperation

STL

STL

STL, DCM, UDX

STL, DCM, UDX

STL, DCM, UDX

PlanCAD Easy, integrated in Planmeca Romexis

Zfx CAD software

3Shape Trios Design Studio Open

3Shape LAB Praxis

3Shape Trios Design Studio Straumann Cares Visual

PlanCAD Easy, integrated in Planmeca Romexis

hyperDENT hyperMILL

3Shape Trios Design Studio PrograMill CAM V4 PrograMill One App

3Shape LAB Praxis Lyra Mill

3Shape Trios Design Studio Straumann Cares Visual Straumann Cares C series

PlanMill 40 S PlanMill 30 S

Zfx Inhouse5x wet & dry

PrograMill One

Lyra Mill

Straumann Cares C series

4 axes

5-axis simultaneous (servo motors A and B axes)

5-axis turn-milling technology (5XT)

4 axes

4 axes

Glass-ceramic, PMMA, composite, hybrid ceramic

Zirconia, glassceramic, CoCr, titanium, PMMA, composite, wax

Ivoclar materials: zirconia, glass-ceramic, PMMA, composite

Glass-ceramic, PMMA, composite, hybrid ceramic

Glass-ceramic, hybrid ceramic

Wet

Wet & dry

Wet

Wet

Wet

Grinding

Milling & grinding

Milling & grinding

Grinding

Milling & grinding

QDT 2018 55

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Table 2 Overview of the Most Common Intraoral Scanning Systems Currently Available 3M Espe (True Definition Scanner)

Align Technology Dentium (iTero (rainbow Element) iOS)

Densys 3D (MIA3D)

GC KaVo (AADVA) (Lythos)

MFI (Condor)

Ormco (Lythos)

Sirona (Apollo DI)

Powder

Yes

No

No

Yes

No

No

No

No

Yes

Color display

No

Yes

Yes

No

No

Yes

Yes

No

No

Imaging mode

Video

Video

Individual images

Video

Video

Video

Video

Video

Video

Imaging principle

Wavefront sampling

Confocal laser technology

Triangula- Triangula- Confocal tion tion laser technology

Digital workflow

Cloudbased platform— 3M Connection Center

Cloudbased platform— My Aligntech

Cloudbased platform

Direct

Cloudbased platform

Cloudbased platform

Direct

Cloudbased platform— Ormco Digital

Cloudbased platform— Cerec Connect

Data export

STL

STL

STL

STL

STL

STL

STL

STL

Closed system: STL (model)

Triangula- Stereopho- Triangulation tion togrammetric video

Confocal laser technology

Intraoral scanning information obtained from Zimmermann et al.16

Restorative Materials The type of material selected for the final restoration is another factor that must be taken into consideration during the tooth preparation. High-strength glass-ceramics, such as lithium disilicate–reinforced glass-ceramic or zirconiareinforced lithium silicate glass-ceramic, have higher Young’s modulus E and flexural strength than feldspar-reinforced aluminosilicate glass, leucite-based glass-ceramic, and

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hybrid materials.17–20 Due to their adequate mechanical (Table 3) and optical properties, high-strength glass-ceramics might be used to mill ultrathin monolithic CAD/CAM restorations, with up to 0.2 mm of thickness (Fig 13).21 The digital workflow allows minimally invasive adhesive restorations that preserve dental structure to its pristine condition, which is the aim of any modern esthetic rehabilitation (Figs 14 to 18).

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Table 3

CAD/CAM Materials: Composition, Indications, and Properties Young’s modulus E (GPa)b

Flexural strength (MPa)c

102.7

609.80

Material

Manufacturer

Composition

Clinical indicationa

e.max CAD

Ivoclar Vivadent

Lithium disilicate glass-ceramic

Veneers, inlays, onlays, anterior and posterior crowns, anterior and posterior implant abutments, three-unit fixed prostheses up to premolars, overlay veneers for multiunit frameworks

Celtra Duo

Dentsply DeTrey

Fully sintered lithium Veneers, inlays, onlays, anterior and posterior crowns silicate/phosphate glass-ceramic

107.9

565.80

Suprinity

VITA Zahnfabrik

Presintered lithium silicate/phosphate glass-ceramic

Veneers, inlays, onlays, anterior and posterior crowns

104.9

537.03

Vitablocs Mark II

VITA Zahnfabrik

Feldspar-reinforced aluminosilicate glass

Veneers, inlays, onlays, anterior and posterior crowns, overlay veneers for multiunit frameworks

71.3

118.65

Empress CAD

Ivoclar Vivadent

Leucite-based glass-ceramic

Veneers, inlays, onlays, anterior and posterior crowns

65.5

187.77

Enamic

VITA Zahnfabrik

Polymer-infiltrated particle-reinforced glass network

Veneers, inlays, onlays, anterior and posterior crowns

37.8

193.45

Lava Ultimate

3M ESPE

Nanoparticulate prepolymerized resin composite

Veneers, inlays, onlays

12.7

300.64

Clinical indication as given by the manufacturer. Values of elastic modulus obtained from Belli et al.19 c Values of flexural strength obtained from Wendler et al.20 a

b

Fig 13 Ultrathin CAD/CAM monolithic restorations milled in high-strength glass-ceramic (IPS e.max CAD) before crystallization.

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14

16

15

17

Fig 14 Restorations etched with 5% hydrofluoric acid, cleaned with 35% phosphoric acid, and silaned. Fig 15 Teeth air abraded with aluminum oxide, etched with 35% phosphoric acid, and bonded using a universal adhesive system. Fig 16 Restorations were adhesively luted using a light-cured resin cement. Excess cement was removed using artistic brushes. Fig 17 Postoperative view of maxillary arch.

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Figs 18a and 18b Postoperative facial views.

QDT 2018 59

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DISCUSSION The use of 3D interdisciplinary computer-assisted treatment planning for diagnosis and treatment phases offers multiple advantages over traditional techniques. It facilitates the communication between different dental team members to produce a multidisciplinary treatment plan with the end result in mind. Visualizing steps virtually allows the health care providers to identify challenges and limitations of the treatment and discuss them with other team members and the patient. However, there are still limitations that the computer cannot predict. It remains very difficult to foresee how the surrounding gingival tissues will appear after orthodontic treatment. Root and/or bone resorption might occur during orthodontic treatment that could result in the definitive gingival level or zenith being different than those aimed for during the virtual orthodontic treatment planning. Those differences may be due to tissue response to the orthodontic forces or discrepancies between the digital data and the actual case. Full-arch digital impressions also have their limitations. Intraoral scanners are still improving and full-arch optical impressions may be inaccurate due to the data distortion during scanning.22 To ensure data accuracy and avoid incompatibility during the treatment planning, the dental team providers should ideally use the same CAD/CAM platform or systems with official cooperation (Tables 1 and 2). Intraoral digital records acquired using the scanner from one system may lose optical impression data, such as color and details, when exported to another system for CAD designing of restorations. Moreover, not all CAD software allows the

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model and restorations to be exported in an open source format, such as STereoLithography (STL). Cross-communication between different digital platforms for orthodontic, oral surgery, and restorative treatment planning and esthetic design is still a challenge. Digital models, CBCT, and proposed restorations normally must be converted and then transferred to dedicated software for orthodontic, implant, and/or restorative treatment. As of today, not all CAD/CAM systems are fully integrated into single dedicated software. 3D digital treatment planning and execution still requires the use of multiple digital platforms to deliver multidisciplinary treatment planning. However, manufacturers are beginning to understand the need for one software that allows the integration of multiple modules for orthodontic treatment, implant placement planning, smile design, and restoration fabrication within one system.

CONCLUSION The treatment of esthetic cases using 3D computerassisted tools still requires a combination of systems encompassing CBCT, 3D digital impression, 2D intra- and extraoral photographs of the patient, and CAD software for better digital treatment planning. For multidisciplinary conservative esthetic and functional rehabilitations, knowledge of digital workflow; ideal teeth proportion, position, and angulation; as well as CAD/CAM materials and systems available is necessary.

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REFERENCES 1. Miyazaki T, Hotta Y, Kunii J, Kuriyama S, Tamaki Y. A review of dental CAD/CAM: Current status and future perspectives from 20 years of experience. Dent Mater J 2009;28:44–56. 2. Zaruba M, Mehl A. Chairside systems: A current review. Int J Comput Dent 2017;20:123–149. 3. Al Mortadi N, Eggbeer D, Lewis J, Williams RJ. CAD/CAM applications in the manufacture of dental appliances. Am J Orthod Dentofacial Orthop 2012;142:727–733. 4. Muller-Hartwich R, Prager TM, Jost-Brinkmann PG. SureSmile— CAD/CAM system for orthodontic treatment planning, simulation and fabrication of customized archwires. Int J Comput Dent 2007; 10:53–62. 5. Coachman C, Calamita M. Digital Smile design: A tool for treatment planning and communication in esthetic dentistry. Quintessence Dent Technol 2012;35:103–111. 6. Dawson PE. Functional Occlusion: From TMJ to Smile Design. St Louis: Mosby Elsevier, 2007. 7. Scholz RP, Sarver DM. Interview with an Insignia doctor: David M. Sarver. Am J Orthod Dentofacial Orthop 2009;136:853–856. 8. Zimmermann M, Mehl A. Virtual smile design systems: A current review. Int J Comput Dent 2015;18:303–317. 9. Kurbad A, Kurbad S. Cerec Smile Design—A software tool for the enhancement of restorations in the esthetic zone. Int J Comput Dent 2013;16:255–269. 10. Cofar F, Cofar I, Stumpf L, Popp I, Pineda A, Van Dooren E. RAW: A digital workflow. Quintessence Dent Technol 2017;40:7–25. 11. Duarte S Jr, Schnider P, Lorezon AP. The importance of width/length ratios of maxillary anterior permanent teeth in esthetic rehabilitation. Eur J Esthet Dent 2008;3:224–234.

12. Coachman C, Calamita MA, Sesma N. From 2D to 3D: Complete digital workflow in interdisciplinary dentistry. J Cosmet Dent 2016;32: 62–74. 13. Kano P, Xavier C, Ferencz JL, Dooren EV, Silva NR. The anatomical shell technique: An approach to improve the esthetic predictability of CAD/CAM restorations. Quintessence Dent Technol 2012;36: 27–36. 14. Clavijo V, Sartori N, Phark J-H, Duarte S. Novel guidelines for bonded ceramic veneers: Part 1. Is tooth preparation truly necessary? Quintessence Dent Technol 2016;39:7–25. 15. Sartori N, Alsamman R, Bocabella L, et al. Biomaterials Update: The adhesive restorative complex (ARC) concept. Quintessence Dent Technol 2017;40:48–65. 16. Zimmermann M, Mehl A, Mormann WH, Reich S. Intraoral scanning systems—A current overview. Int J Comput Dent 2015;18:101–129. 17. Anusavice KJ. Phillips’ Science of Dental Materials. St Louis, MO: Elsevier, 2013. 18. Guess PC, Selz CF, Steinhart YN, Stampf S, Strub JR. Prospective clinical split-mouth study of pressed and CAD/CAM all-ceramic partial-coverage restorations: 7-year results. Int J Prosthodont 2013; 26:21–25. 19. Belli R, Wendler M, de Ligny D, et al. Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization. Dent Mater 2017;33:84–98. 20. Wendler M, Belli R, Petschelt A, et al. Chairside CAD/CAM materials. Part 2: Flexural strength testing. Dent Mater 2017;33:99–109. 21. Sartori N, GilbertoTostado, Phark J-H, KazunariTakanashi, Lin R, Duarte S. Biomaterials Update: CAD/CAM high-strength glassceramic. Quintessence Dent Technol 2015;38:39–54. 22. Muallah J, Wesemann C, Nowak R, et al. Accuracy of full-arch scans using intraoral and extraoral scanners: An in vitro study using a new method of evaluation. Int J Comput Dent 2017;20:151–164.

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A New Tool for the Prosthetic Treatment Plan: Use of Minimally Invasive Prosthetic Procedures (MIPP) and GETApp

T

he purpose of all prosthetic rehabilitations should be to (1) restore optimal esthetics, (2) balance or maintain the healthy status of the stomatognathic system, and (3) ultimately perform minimally invasive treatment. This is now possible by following the fundamentals of Minimally Invasive Prosthetic Procedures (MIPP), described by Fradeani et al.1 In order to achieve the first goal, the clinician must perform a precise esthetic analysis, having a good knowledge of which parameters are to be analyzed and, if necessary, corrected. For the second goal, it is necessary to perform an appropriate functional analysis by first analyzing whether the stomatognathic system is in balance or if one or more of its components (joints, muscles, teeth) are compromised and suffering. In addition, the purpose of functional analysis should be to collect all data relating to the functional parameters of the patient, compare them to those considered to be more physiological, and evaluate whether it is possible to optimize them through prosthetic rehabilitation—all that to improve the health of the stomatognathic system, should it be necessary. Even in the

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Leonardo Bacherini, DDS1 Leonardo Bocabella, CDT2 Mauro Fradeani, MD, DDS3

Private Practice, Sieci, Firenze, Italy. Dental Technician, Campinas, São Paulo, Brazil. 3 Private Practice, Pesaro, Italy. 1 2

Correspondence to: Dr Leonardo Bacherini, Studio Odontoiatrico, Piazza Aldo Moro, 7, 50065 Sieci FI, Italy. Email: [email protected]

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www.pdflobby.com BACHERINI ET AL absence of a real illness of one of the components of the system or of a parafunction, the clinician should try to observe the ideal occlusal parameters in order to improve the stability of the prosthetic result and achieve long-lasting restorations. For the third goal, to perform minimally invasive treatment, it is important to establish an ideal treatment plan by correctly processing the data collected in the previous two steps and develop some specific skills needed to perform a minimally invasive tooth preparation. From these considerations, it is clear that the treatment plan is the key element of the minimally invasive prosthetic rehabilitation. In this stage, the clinician must be able to collect and process different information at the same time—often an unpleasant obstacle to overcome for the untrained clinician. A few years ago, Fradeani2 proposed a systematic approach to prosthetic rehabilitation that clearly described how to correctly collect all the esthetic and functional parameters needed to formulate the treatment plan. After collecting all the data, the clinician should be able to process them, formulate the treatment plan, and, thanks to the laboratory chart, send all the information to the dental laboratory so that the technician can perform the diagnostic wax-up, which represents the real prototype of the definitive work. Recently, given the many requests by dentists for support in treatment planning and the availability of innovative technologies capable of simplifying and accelerating many prosthetic procedures, a new application was designed. GETApp (Guided Esthetic Treatment Application) assists the clinician in all phases of data collection and processing, and it can also interact with various technological tools available in the different steps of the prosthetic treatment (intraoral scanners, milling machines, 3D printers, etc) for a fully digital workflow of the rehabilitation. The collected data are eventually processed by the application so to propose an ideal prosthetic treatment plan. GETApp was developed following the Fradeani systematic approach for data collection. In addition to offering the opportunity to automatically process these data, the application offers a treatment plan proposal. The treatment option suggested can be modified at any time by the clinician, who can keep possible changes under check thanks to GETApp, which constantly verifies whether the inserted parameters are appropriate. During the process, all the various steps and the purpose of each action are explained in detail; therefore, GETApp

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is also an efficient learning instrument for the clinician who may not have received specific training in simple and complex prosthetic rehabilitation. This instrument can be considered an updated and simplified digital version of the concepts described in Mauro Fradeani’s book.2 After processing the data, GETApp produces a pdf that contains all the information that will enable the technician to design the rehabilitation. Communicating with the dental technician has always been considered fundamental to prosthetic rehabilitation. For this reason it is very important that the clinician uses a reliable instrument to ensure effective communication with the laboratory. Following are the benefits and possibilities GETApp offers the clinician: • Collection of data for the patient’s anamnesis (the GETApp system can replace medical records) • Collection of all the clinical data necessary for proper communication with the dental team (radiographs, periodontal chart, health state of each tooth, tooth color, previous dental treatments to be redone, stomatognathic dysfunctions) • A guided and predictable method for dental photography and case documentation • Collection of all esthetic and functional values necessary for formulating the treatment plan • Complete and automatized support in formulating the treatment plan • Effective communication with the dental lab • Effective communication with the patient GETApp is a useful instrument in preparing a complete esthetic and functional treatment plan, but it does not offer any suggestion on the methods to be used in treating teeth that are damaged from a biologic and structural point of view. The final decision on how to treat a tooth or whether to replace it is made by the clinician. GETApp is structured in two distinct phases: (1) data collection (fully guided and can be done also by an assistant) and (2) data processing that can be done either with the patient in the chair or at a different time. At the end of the process, the app will generate a pdf file with all the indications for the technician to carry out a diagnostic wax-up for the mock-up and for the final restoration. This article will show, through a clinical case, how GETApp works with both a traditional prosthetic approach and an entirely digital approach. Note that GETApp is available only for tablets.

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1

2a

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Fig 1 Patient’s face preoperatively. Figs 2a to 2c Photographs for dentolabial evaluation.

PATIENT PRESENTATION The patient, a 35-year-old woman, was concerned with the esthetics of her anterior teeth. She wanted to improve her smile, as she thought her teeth were small and had an unpleasant color. Preoperative photographs and cast images are shown in Figs 1 to 4. During the patient’s first visit she was interviewed to understand her motivation in undertaking a prosthetic reha-

bilitation and consequently the possibility of proceeding with the use of the app to formulate the treatment plan. As the patient was eager to improve her smile, the decision was made to proceed and use the app in a very brief second appointment for the data collection. The appointment for data collection carried out with the app normally takes only a few minutes, but complete full-mouth radiographs can also be taken at this time to assess the mouth’s state of health.

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3b

3a

4a

4b

4c

Figs 3a and 3b Photographs showing shape, proportion, arrangement, and color of the maxillary and mandibular teeth. Figs 4a to 4c Patient’s occlusion.

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5a

5b

5c

5d

Figs 5a to 5d Data collection phase with GETApp. In step 1, the clinician has to collect both generic data, such as the patient’s medical history, and specific details regarding the patient’s teeth.

DATA COLLECTION WITH GETAPP Step 1: Patient In this step, the patient’s general information is taken. Some information is mandatory and very important, as it allows the app to process the best treatment plan according to the esthetic parameters of reference. Among these data, particular relevance is given to the age and sex of the patient, as these parameters are associated with different levels of tooth exposure at rest.

Other information collected in this step are: subjective perception, treatment requested by the patient, objective examination, and skeletal class. There is also the option to collect data on the patient’s medical history. For this patient, it was clear in this step that she had marked nonphysiological wear of the anterior teeth, which represented her main esthetic concern. The patient also requested that the color and dimension of her teeth be altered. Her requests were therefore to have aligned, white, youthful-looking teeth with treatment limited to the maxillary anterior teeth. Her skeletal class was Class 1 (Figs 5a to 5d).

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6b

6a

Figs 6a to 6c Photographs are necessary for the formulation of the treatment plan. A fixed number of photographs is required by the tool. The presence of a level allows the clinician to take each photograph correctly, and a complete guide makes the process easy and fast. The appropriate inclination of the device is fundamental to consider the horizon as a reference line, thus determining the orientation of the rehabilitation. Videos are also important for dynamic analysis of the esthetic and functional parameters.

6c

Step 2: Photographs and Videos The most important step in data collection is photo shooting. The photographs will be used in the data processing phase for some decisive measurements when formulating the treatment plan (Figs 6a to 6c). The photographs taken with GETApp are always correctly oriented according to the horizon. It is essential that the patient’s head is in a natural position and that the tablet is correctly oriented (check the spirit level). This set-up will enable the clinician to analyze some reference lines on the patient’s photographs, compare them with the horizon, and define which line is to be followed to correctly orient the rehabilitation. The clinician is guided by GETApp during the photo shooting, so errors by those not so familiar with dental photography for diagnostic purposes are avoided. It can be said that the GETApp acts as a digital facebow.

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Short videos can also be recorded for the dynamic analysis of some esthetic and functional parameters. Some examples are provided to indicate to the patient the correct position and the facial expressions to be assumed.

Step 3: Dentolabial Analysis In this step, data are collected concerning the relationship between the patient’s lips and teeth (Figs 7a to 7c). Among the most important data to be collected is the smile line, which is used to optimize the final appearance of the restorations. If the smile line is high, the app would be set to optimize the exposure at rest, the proportion of the teeth, and the appearance of the tissues during the preparation of the treatment plan. If the smile line is low, the parameter of reference would be only the exposure at rest, which

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7a

7b

7c

Figs 7a to 7c In step 3, more data regarding important esthetic parameters are collected, as per the systematic approach described by Fradeani.2

we know is the starting point for any prosthetic rehabilitation. Other esthetic parameters analyzed in this step are the labial corridor, smile width, interincisal line inclination, and interincisal line versus upper lip philtrum. This patient had an average smile line, a normal labial corridor, visibility of 10 teeth in the maxillary arch, a vertical

interincisal line, and a centered interincisal line with the labial philtrum. It was therefore necessary to optimize the dental proportions and the appearance of the tissues. This was taken into account by the app, which chose the proper method of data processing when automatically determining the central incisal margin position.

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8a

8b

8c

Figs 8a to 8c The tool guides the clinician in the collection of data concerning esthetics, such as tooth dimension and exposure at rest, as well as functional parameters, such as the relationship between maxillary and mandibular anterior teeth. All data will be automatically processed by GETApp for the optimization of esthetics and function. Figs 9a and 9b In formulating a treatment plan, the clinician can overlook functional parameters of the mandibular anterior teeth that can be important to optimize the patient’s occlusion. In step 4, GETApp allows the clinician to evaluate two important parameters: the inclination of the mandibular anterior teeth and the relationship between the mandibular posterior and anterior occlusal planes.

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9a

9b

Step 4: Dental Analysis In this step, both esthetic and functional data are collected, as the purpose of the whole process is not only to optimize the esthetic appearance of the anterior teeth but also to cross-reference the functional data (overbite and overjet) with esthetic data in order to optimize the anterior dental relationship. All this is done to obtain restorations that are in harmony with the patient’s stomatognathic system and to determine an appropriate anterior guidance (Figs 8a to 8c). Data are collected on the size of the teeth (length and width), exposure at rest, overbite value, overjet value, presence or absence of contact between maxillary and mandibular anterior teeth, dental wear, measurement of the thickness of the incisal margin of the maxillary central incisors, and the presence or absence of palatal wear. Additional data on the mandibular teeth will also be very important: in particular, the presence of overeruption or undereruption of the mandibular anterior teeth and their inclination with regard to the occlusal plane. All the data collected in this step will be processed and cross-matched

with data already collected in step 1. However, it will be very useful also for step 9, which will graphically show the relationship between the incisors before, during, and at the end of the data processing. The important data for this patient were the dimensions of the maxillary incisors, which were totally incorrect in terms of the length-width ratio, and exposure at rest, which even though minimal was not ideal for the age and sex of the patient. Furthermore, she presented a reduced overjet, considerable wear of the incisor margin, and wear of the palatal surface of the maxillary incisors. The mandibular teeth were slightly overerupted (approximately 0.5 mm) and lingually inclined (Figs 9a and 9b).

Step 5: Optional Data In this step, the clinician may want to collect some additional optional data relating to information about tooth color, endodontically treated teeth, remaining dental structure, and/or periodontal health.

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10a

Figs 10a to 10d The formulation of the treatment plan starts with the “data processing” of some esthetic parameters of the patient’s face. Note in Fig 10b the red advancement line in the circular diagram indicates an incorrect proportion of the lower third of the face. In this case, an alert will suggest analysis to be performed by an orthodontist and orthognathic surgeon.

10b

DATA PROCESSING The advantage of GETApp compared to other applications already on the market is that it is not limited to the optimization of the patient’s smile but also considers the reestablishment of an ideal occlusion. The purpose is to understand if the esthetic modifications that are planned for the anterior teeth will be in harmony with the new occlusion, meaning the new relationship between the maxillary and mandibular anterior teeth (anterior guidance). The app can maintain all the esthetic and functional aspects and at the same time optimize them, proposing a valid treatment from all points of view. The app works using specific color codes: red, green, and orange. When the numbers showing the esthetic and functional parameters are red, they are outside an acceptable range. Green numbers identify an ideal value, whereas orange numbers can be considered acceptable. At any time and in every screen,

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it is possible to use an appropriate button to recall important information regarding how to correctly carry out the steps and how to process and manage the data. The question-mark button can be used to view how and why to interact with the various active buttons present on the screen. The system does not permit continuing to the next step until the function on screen has been completed.

Step 6: Face Data Processing Data relating to the patient’s face, such as the dimensions of the three thirds of the face, profile analysis, and the position of the maxillary incisor with the Andrews method, are processed in this step (Figs 10a to 10d). The purpose is to identify important esthetic anomalies in the patient’s face and offer recommendations for treatment. Should any values appear red, the app, before proceeding, will show an

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10c

10d

alert and suggest a consultation with an orthodontist and orthognathic surgeon, or the possibility to accept an esthetic compromise and proceed with prosthetic treatment (Fig 10b). For this patient, all the data were within normal limits.

Step 7: Dentolabial Processing—Frontal This step is of particular importance, as it establishes the position of the incisal edge from the vertical/frontal point of view. We know that every prosthetic rehabilitation begins by defining the position of the incisal crest and then continues with the optimization of the functional parameters. The first part of this step involves defining the orientation of the rehabilitation. The possibility of taking photographs, correctly showing the natural position of the patient’s head, allows the app to work like a facebow. It will

therefore be possible to have the horizon as a reference and consequently the relationship of the bipupillary line with it. The clinician can therefore decide whether to follow the horizon or the bipupillary line in the orientation of the rehabilitation (Fig 11). GETApp will next automatically establish the ideal length of the central incisor taken as a reference. This means that the app, given the fact that the smile line is average and therefore that the proportions of the incisor must be optimized, will cross-reference the various lengthwidth measurements and exposure at rest to find the best compromise among them and establish the correct position of the incisal margin. Once the values have been obtained from the app, the clinician may decide to modify them in order to change the dimensions of the incisors and have the opportunity to control the validity of the lengthwidth ratio at each modification (ideally between 75% and 85%) and exposure at rest (Figs 12a to 12d).

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11

12a

12b

Once the incisal margin of the maxillary central incisors has been positioned, it will be necessary to position the incisal margin of the canines. The clinician has the opportunity to use a mask to establish the ideal curvature of the maxillary arch, and to decide on the position of the tip of the canines and then later also that of the premolars and

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molars, depending on the extension of the selected treatment (6 to 8 teeth or 10 or 12 teeth). In this patient, the bipupillary line was chosen as a reference for the rehabilitation, as this differed from the horizon line by only a few degrees. Following the automatic procedure undertaken to optimize all the esthetic parameters of

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12c

12d

Fig 11 In step 7 it is possible to analyze reference lines such as the bipupillary line and occlusal plane, and to compare them with the horizon. The clinician will be able to define the orientation of the rehabilitation by following either the bipupillary line or the horizon; in this way, the application acts like a digital facebow. Figs 12a to 12d GETApp presents several esthetic parameters regarding the maxillary anterior teeth, with the aim of optimizing the exposure at rest and the tooth proportions. This will determine the position of the incisal edge of the maxillary teeth, the starting point of the formulation of any treatment plan.

dental exposure and dental proportion, the app recommended lengthening the central incisors 1.8 mm. In this way, all the parameters were green. At the request to undertake manual modifications, NO was selected, as everything resulted as being ideal. Lengthening both the right and left canines 1 mm was suggested.

Step 8: Dentolabial Processing— Lateral This step defines the position of the incisal crest in a buccolingual direction, or lateral point of view. For this verifica-

tion and possible modification of the position of the incisal margin of the central incisor of reference, the app will take into consideration the angle formed by the Camper plane and the tangent at the vestibular surface of the incisor as well as phonetic analysis with the use of “F” and “S” phonemes. For every degree of deviation from the value considered as being normal, the app offers a precise movement in millimeters in a palatal or buccal direction. Should this be in disagreement with the phonetic analysis, it would be signaled as an error. This procedure is guided and therefore the clinician is able to avoid errors of excessive vestibular extension and lingualization of the incisal margin. Furthermore, the app is able to advise a possible vestibular move-

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13a

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Figs 13a to 13c Once the position of the incisal edge of the central incisor is set from a frontal point of view, the application will lead to the determination of the ideal position of the incisal margin from a lateral point of view. In this process the inclination of the central incisor will be considered and compared with the position of the incisal margin with reference to the lower lip vermilion during the pronunciation of the “F” or “S” sound.

ment of the margin to reduce the invasiveness of the prosthetic treatment. An alert appears in the case of excessive lingualization, implying the treatment is too aggressive. This patient required 1.2 mm buccal movement of the incisal margin. This was also considered to be correct from a phonetic point of view, as pronunciation of the phoneme “F” resulted in the incisal margin being lingualized by 2 mm (Figs 13a to 13c).

Step 9: Treatment Plan Formulation Once the esthetic optimization of the teeth in the maxillary arch is completed, the new occlusal relationship at the level of the maxillary and mandibular central incisors is evaluated. Following the esthetic changes, an incorrect

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overjet-overbite ratio can occur. If so, the clinician will have to adjust the treatment plan to return this parameter to optimum values. The most important step of the app has been reached now—formulation of the treatment plan, namely the optimization of function with definition of the correct anterior guidance. To achieve functional optimization, in this step it is possible to also modify the patient’s vertical dimension of occlusion (VDO) and all the esthetic parameters already given. At the same time it will be possible to view the changes, in real time, with a graphical view of the ratio between the incisors before, during, and after the changes. The clinician, always keeping the numerical values and their relative colors under control, can modify what has already been entered in order for everything to fall within the ideal values (Figs 14 and 15).

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Figs 14a and 14b Step 9 is the most important step in the process of treatment plan formulation. The clinician is guided by the app in the examination of the functional aspects of the rehabilitation, after having optimized the esthetic parameters. Often the final overjet and overbite of the patient are not ideal, causing the anterior guidance of the final rehabilitation to be incorrect. Since the goal of every treatment is the optimization of esthetics and function, the clinician may need to modify some of the already set esthetic parameters in accordance with important functional values such as the VDO. GETApp allows the clinician to have full control of the esthetic and functional parameters in order to define an ideal treatment plan. Figs 15a and 15b Information provided by the app that guide the clinician in the decision-making process for an ideal treatment plan.

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www.pdflobby.com BACHERINI ET AL Choosing a correct treatment plan also involves evaluating the possibility of treating the posterior teeth. Often the clinician concentrates only on the maxillary anterior teeth because this is what the patient wants. However, if the purpose of every treatment should be to restore both esthetics and function, the presence of mandibular defects (wear, incorrect inclination, or altered eruption of the anterior teeth) means treatment should be extended also to the mandibular teeth. GETApp proves to be extremely helpful for the clinician in completing analysis of the patient’s mouth, in detecting possible defects of the mandibular teeth, and in deciding whether to treat only the anterior teeth, the posterior teeth, or both. Modifying some functional parameters such as the VDO requires advanced prosthetic knowledge (eg, how to distribute the VDO increase between the maxilla and mandible). Some useful notes are available to help the clinician in this delicate decision. In this step, GETApp offers another useful aid regarding the procedures for optimization of the overjet-overbite. In this patient, after the evaluation of a new overjetoverbite ratio created by the previous modifications, the decision was made to increase the VDO by 3 mm. The overbite resulting from the modification of the length for esthetic purposes was 6.3 mm, unacceptable from a functional point of view. Furthermore, considering the lingual inclination and wear of the mandibular teeth, it was decided to treat them and at the same time increase the overjet, which from the start was at the minimum value. The VDO was increased gradually, in 1-mm increments, until it was possible to achieve an acceptable overbite value (4.1 mm), an ideal overjet value (2.9 mm), and a new inclination of the mandibular incisors (approximately 90 degrees to the occlusal plane); all the esthetic parameters were green at the same time, therefore optimal. At this point, considering that the space created at the occlusal level was still not closed (lack of contact between the maxillary and mandibular central incisors) and that the position of the incisal margin of the mandibular teeth could not be modified (moved coronally), the decision was made to cover the palatal surface of the maxillary incisors. By so doing, it was possible to define the type of restoration for the maxillary anterior teeth (full veneers). Ultimately, the procedure followed in this step echoes what should be the ideal method to define the relation between the incisors and at the same time the optimal VDO: first establish the position of the incisal margin of the maxillary incisors, then the position of the incisal margin of the

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mandibular incisors, and finally the correct VDO to obtain the ideal overbite and overjet values.

Step 10: Teeth Arrangement This step processes information concerning the arrangement of the six anterior teeth in the maxillary and mandibular arches. Up to this step only the position of the two maxillary and mandibular incisors of reference has been established, but now the modifications of all the other teeth must be communicated to the technician to complete the wax-up of the case. A modification of rotation can also be defined, as well as the overall palatal or vestibular shift of the entire crown. In this patient, given her request to have aligned teeth, indications were given to the technician to move all the maxillary and mandibular teeth to attain this result.

Step 11: Laboratory Chart A series of parameters are selected in this step to communicate to the technician how to set the articulator and the type of restoration to be fabricated. It states in detail the following information: • • • • • • • •

Mock-up masks Provisional or final restoration work Functional aspects (eg, canine guide or group function) Functional values to set on the articulator (average or individual values) Types of silicone indexes necessary for rehabilitation Type of restoration for each tooth in both arches (full coverage, buccal coverage, occlusal coverage) Choice of restoration material for each tooth Choice of color

For this patient, the technician was asked to carry out the diagnostic wax-up and the relative masks for the mockup. He was asked to work on an articulator with average values to obtain an anterior and canine guidance. The values to be set in the articulator were all standard values (immediate Bennett shift, 0 degrees; Bennett angle, 10 degrees; condylar eminence angle, 25 degrees). Considering the result obtained in step 9, it was decided to fabricate full veneers (lithium disilicate ceramic, layered only in the vestibular part) for the maxillary anterior teeth,

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16a

16b

Figs 16a and 16b Final pdf, processed by GETApp, with all the information necessary for the technician to design the case. This pdf can be referred to either an analog procedure associated with the traditional facebow or to a digital workflow in combination with the Face Hunter system (Zirkonzahn).

buccal veneers (layered lithium disilicate ceramic) for the mandibular anterior teeth, and occlusal veneers (monolithic lithium disilicate ceramic) for the mandibular posterior teeth. The selected color was A1 in the Vitapan shade guide. The selected ceramic material was e.max Ceramic MT AI (Ivoclar Vivadent).

Step 12: Summary Final Notes In this step, it is possible to graphically view all the modifications to be undertaken on each tooth included in the treatment in order to wax the case: • • • •

Frontal view: length and width modifications Occlusal view: buccolingual shift of the incisal margins Initial functional aspects Final functional aspects

• Type of restoration to be fabricated • Additional notes, if necessary

Step 13: Review This final step closes the procedure, indicating the delivery date of the work. The GETApp creates a pdf file that is sent to the technician or shared with the dental team (Figs 16a and 16b). The treatment plan formulated by the app could require additional orthodontic or surgical treatment, as mentioned earlier. If this is necessary, it is possible to share with the orthodontist and orthognathic surgeon information about how and how much to move the teeth (extrusions, intrusions, buccolingual shifts, or derotations) and/or how much to move the cervical margins (coronally or apically).

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PROSTHETIC TREATMENT SEQUENCE Once the treatment plan has been defined with the use of GETApp, the prosthetic rehabilitation can proceed with either a traditional method or a completely digital workflow (Figs 17 to 51).

Traditional Method The pdf with the indications for the diagnostic wax-up was sent by email to the dental technician together with the silicone impressions of the dental arches and the centric relation (Dawson maneuver3 and the use of a wax) and facebow registrations. Thanks to the idealization of the treatment plan and the precise definition of the VDO increase (step 9), the wax for centric relation registration can be registered at the VDO at which the work will be finalized. Once all the information was received, the technician mounted the models in the articulator, carried out the diagnostic wax-up, and fabricated the silicone indexes for the mock-up. The mock-up was carried out with a bis-acrylic resin on both arches and was adjusted with a selective grinding procedure to guide the mandible in centric relation. The mock-up was then reevaluated from an esthetic and functional point of view in order to obtain well-distributed contacts on the posterior teeth, delicate contacts on the anterior teeth, and presence of an appropriate anterior and canine guidance. The ratio between overbite and overjet,

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due to the precise planning with GETApp, was perfectly replicated as shown in the diagram in step 9. Once the mock-up was confirmed, an impression was taken, as this was going to be used as a guide for the technician to fabricate the final restorations. The mock-up was also used as a guide to carry out the preparations of the mandibular posterior restorations. Minimally invasive tooth preparations were made with the aim of preserving all the enamel for buccal-occlusal veneers either with the contact points maintained or removed. The decision to open or not to open points of contact depended on the presence of interproximal defects (caries or composite restorations). When the preparations were finished, impressions were taken using the traditional technique (one-step double mix), with the use of a metal tray and silicone material (polyvinyl siloxane, light body and heavy body). Together with the impressions, the facebow was recorded once again. Thanks to the presence on the anterior mock-up that keeps the mandible in centric relation at the new VDO, a bite registration between the posterior prepared teeth was taken. After the model was mounted in the articulator, the dental technician carried out the wax-up for the definitive restoration of the posterior teeth. These were made in monolithic lithium disilicate ceramic (e.max Press, Ivoclar Vivadent) with a press technique. At the next appointment, the posterior restorations were cemented using an adhesive technique and the occlusal adjustment was done with selective grinding to guide the mandible again in centric relation with the Dawson maneuver. The maxillary and mandibular teeth were also prepared

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www.pdflobby.com A New Tool for the Prosthetic Treatment Plan: Use of Minimally Invasive Prosthetic Procedures (MIPP) and GETApp during the same appointment. A specific design to prepare the maxillary anterior teeth was developed to keep the contact points unaltered, while at the same time to cover both the vestibular and palatal areas with one unique restoration (“V” veneer) (Figs 35a to 35d). With this technique, it is not necessary to perform two different restorations with two different materials, reducing the invasiveness of the treatment. As can be seen in Figs 33a to 33c, the enamel completely covered the portion of the prepared tooth. For this reason, no anesthesia was needed to perform the tooth preparation. To prepare the mandibular anterior teeth, a conventional design for vestibular veneers was chosen, opening the contact point. Once the preparations were completed, impressions were taken using the conventional technique as described above. The impressions were once again sent to the lab, together with a new facebow registration. All the information on the type of restoration and material to be used was already in the pdf initially sent to the technician via GETApp. After reassembling the models in the articulator, the technician was able to do the wax-up for fabrication of the final anterior restorations. In order to obtain extremely resistant maxillary restorations, all palatal surfaces were made in monolithic lithium disilicate to completely support the layering ceramic at the incisal margin (Figs 34a to 34c). This is the best compromise between esthetics and strength for full-coverage restorations in a patient with a high risk of chipping. After the restorations were fabricated, they were tried in and, after further finishing modifications, were cemented using an adhesive technique. The restorations were then adjusted occlusally in order to have an adequate distribution of contacts, both static (centric relation) and dynamic (edge-to-edge in protrusive). Postcementation checks and final photographs took place after 1 week.

Fully Digital Workflow After the pdf was produced and sent to the dental technician as in the traditional method, digital impressions were taken (True Definition Scanner, 3M) and a facial scan of the patient with different expressions was taken (Face Hunter Scanner, Zirkonzahn). The facial scans were also taken with an instrument to define the patient’s natural

head position and consequently evaluate some horizontal reference lines of the face in relation to the horizon (Plan Finder, Udo Plaster). In this way, after having transformed the patient’s real image into a virtual image and after overlapping digital impressions with digital facial images, it will always be possible for the dental technician to have the horizon as a reference to correctly perform the virtual diagnostic wax-up. The virtual wax-up will therefore be performed following the indications of GETApp but with the possibility of seeing, in real time, the validity of the digital prosthetic design in different virtual images, with different facial expressions. This is certainly one of the most interesting aspects of the digital procedure even if the representation of the patient will always be static and nondynamic. It will therefore not be possible to evaluate the digital design with the various phases and expressions of facial mimicry. Once the digital mock-up has been made, respecting anterior guidance parameters shown in step 9, the technician is able to fabricate very thin shells of PMMA resin using CAD/CAM technology. This digital mock-up (snapon) will be used for the esthetic and functional evaluation in the patient’s mouth. It can be adjusted to proceed with the tooth preparation steps, as performed in the traditional procedure. The digital impressions will then be done and sent to the laboratory, where they will be inserted into the digital articulator for the final modeling. The restorations for the mandibular posterior teeth were made in monolithic lithium disilicate ceramic using CAD/ CAM technology and then compared in terms of accuracy with those made with a press technique, as mentioned previously. Since the restorations made with the press technique were considered slightly more precise for all the teeth fabricated, they were chosen for final cementation. Once the posterior restorations were cemented as previously described, the anterior teeth were prepared and a digital impression was registered. With the digital impressions, the dental technician fabricated the anterior restorations in monolithic and layered lithium disilicate using the same design previously described. The final restorations made with the digital workflow were compared in terms of accuracy with those produced with a traditional impression, both on stone models and in the patient’s mouth. Those produced with the digital workflow were slightly less precise, so it was decided to finalize the restorations using the traditional technique (Fig 37).

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Figs 17a and 17b Traditional and digital centric relation records. Figs 18a to 18e Traditional wax-up performed following the indications provided by GETApp.

Traditional vs Digital Workflow Consider the following comparisons between a traditional and a completely digital workflow:

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Formulation of the treatment plan: There are significant

advantages with digital technology thanks to the use of GETApp, which facilitates data collection, allows for correct processing of these data, and provides a complete (and in some phases, automatic) guide for the optimization of esthetic and functional parameters of the patient.

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Design of the prosthetic work: The combination of GETApp

Fabrication of the restoration: In the case described herein,

with an intraoral scanner, facial scanner, and Plane Finder allows absolute control and previsualization of the not-yetideal (nondynamic) prosthetic design, but which is better than the traditional method.

with its unusual restoration designs and extremely limited thickness of the final restorations, the traditional technique was found to be superior in terms of precision and marginal adaptation compared to the CAD/CAM procedure.

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Figs 19a to 19e Digital procedure for the design of the rehabilitation following the indications of GETApp. With the use of the Face Hunter system, it is possible to previsualize the esthetic outcome.

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GETApp Design

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Figs 20a and 20b Initial and final relationship between the anterior teeth with the mock-up. The app allows the clinician to previsualize the overbite-overjet ratio, which will have to be replicated in the patient’s mouth with the mock-up. Figs 21a and 21b Esthetic evaluation of the mock-up in reference to the face of the patient.

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Fig 22 Before and after the mock-up. Note the VDO increase. Figs 23a and 23b Dentolabial evaluation with the mock-up. Fig 24 Snap-on mock-up fabricated in PMMA resin using CAD/CAM technology. Figs 25a and 25b Dentolabial evaluation of the snap-on mock-up.

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Fig 26 Comparison between traditional and digital mock-up. Note the difference in the definition of the final shape and volume. The traditional mock-up is still considered best for precise definition of the final design of the restoration and evaluation by the patient. Figs 27a and 27b Final preparation of the mandibular posterior teeth.

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Figs 28a to 28c Buccal-occlusal veneers for the mandibular posterior teeth. Note the amount of enamel remaining after preparation. Fig 29 The digital procedure to define the margin of the preparation and to fabricate final restorations as precisely as possible.

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Fig 30 Comparison between (left) traditionally and (right) digitally fabricated restorations. Figs 31a to 31d Tooth preparation of the maxillary anterior teeth following the mock-up. The traditional mock-up proved to be more precise, thus being the best guide to perfectly calibrate tooth reduction during the preparation. Fig 32 Final preparation maintaining contact points. With this type of preparation, it is possible to fabricate a single restoration to cover both the palatal and buccal areas.

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Figs 33a to 33c Remaining amount of enamel on the tooth surface after preparation.

Layering porcelain e.max ingot

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Figs 34a to 34c Design of the framework supporting the layering ceramic on the buccal side. The palatal side up to the incisal margin was fabricated in monolithic lithium disilicate ceramic. Figs 35a to 35d The “V” veneers. Note the accuracy of the margins.

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Figs 36a to 36c Try-in of the “V” veneers. Figs 37a and 37b CAD/CAM procedure to fabricate the restorations. The accuracy of the final restorations is inferior to that of restorations fabricated with the traditional technique.

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Fig 38 Definitive restorations after the cementation. Fig 39 Occlusal view of the maxillary anterior restorations. Fig 40 Patient’s new occlusion. Fig 41 Final lateral views. Fig 42 Patient’s protrusive mandibular movement with appropriate anterior and canine guidance. Fig 43 Lateral views of the final occlusion. 40

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Initial

GetApp Design

Final

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Fig 44 Initial and final relationship between the central incisors. Note the overjet increase and the new anterior guidance, which is flatter than the original. Fig 45 Development of the treatment. With GETApp it was possible to idealize the overjet-overbite ratio and replicate it on the final restoration. Fig 46 Initial and final overjet.

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Figs 47a to 47d Final smile views of the patient. Fig 48 Final views showing the texture obtained with the traditionally fabricated restorations. Fig 49 Pre- and posttreatment facial photographs.

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Fig 50 Final photographs with different amounts of tooth exposure. Figs 51a and 51b Final portrait photographs.

ACKNOWLEDGMENTS The authors would like to thank Antonio Corradini, MDT, for the digital workflow and the fabrication of the snap-on mock-up.

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REFERENCES 1. Fradeani M, Bacherini L, Brennan M. Esthetic rehabilitation of a severely worn dentition with minimally invasive prosthetic procedure (MIPP). Int J Periodontics Restorative Dent 2012;32:135–137. 2. Fradeani M. Esthetic Rehabilitation in Fixed Prosthodontics: Esthetic Analysis. Chicago: Quintessence, 2004:28. 3. Dawson PE. Functional Occlusion: From TMJ to Smile Design. St Louis: Mosby/Elsevier, 2007.

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Focus Stacking Macro Photography: Achieving Ultra-High Resolution and High Magnification in Dentistry

Carlos A. Ayala Paz, DDS, MS Orthodontist Cayetano Heredia University, Lima, Peru Email: [email protected] Website: www.flickr.com/photos/carlos_ayala

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M

acro photography is essential in dentistry for documentation, record keeping, and communicating among colleagues and patients. However, one of the greatest benefits of macro photography in dentistry is its role in the learning process, since dental photography can be used as an educational tool.

Different techniques and the use of adapted lenses and optics are sometimes necessary to capture the beauty of the dental structures. One of the most sensitive areas of macro photography is control of the depth of field. Only through understanding the depth of field can one capture the beauty of the macro world.

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www.pdflobby.com AYALA PAZ

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Figs 1 and 2 Reproduction ratio of 100-mm macro lens, from 1:1 at 0.3 meters of working distance to 1:10 at 1.25 meters of working distance—in a full frame sensor. Fig 3a Flat sample (zirconia) milled by CAD/CAM at 1:1 with a 100-mm macro lens at f/22 with depth of field of 3 mm. Fig 3b Same sample magnified at 5:1 (5×) with a depth of field of 0.02 mm (20 µm) in a microscope objective with f/0.25 diaphragm value.

Macro lenses (100 mm and 60 mm) are essential for capturing the details of the oral cavity. When using a closed aperture (f/32) with a 100- to 105-mm macro lens at maximum proximity, one is only able to get a depth of field of 6 mm. Conversely, with a 60-mm macro lens at maximum proximity, one is able to get a depth of field of 12 mm. Most photographic lenses are not capable of magnifying beyond 1:1. Macro lenses are able to reach a 1:1 reproduction ratio (1× at maximum lens proximity/life-size or real projection), 1:2 (reduction of half the actual size), 1:4 (reduction of one-fourth), and up to 1:10 (reduction of one-tenth) (Figs 1 and 2). However, some special lenses are capable of magnification above 1:1. For example, Canon MPE-65 is a macro

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lens capable of 1:1, 2:1 (2×, or double magnification), 3:1, 4:1, and up to 5:1 (5× magnification). As the magnification increases, the depth of field and useful focused area decrease. For example, at a magnification of 5:1, the depth of field will be reduced to only 0.5 mm, even in the most closed aperture (eg, f/16 of Canon MPE-65). The result would be a final image that is useless (Figs 3a and 3b). For an adequate depth of field in dental photography, a small aperture should be used (f/22, f/32, or smaller). In such small apertures, an optical phenomenon—known as diffraction of light—occurs when the path of light is altered as it passes through the small aperture; this causes a decrease in sharpness that can be seen at magnifications greater than 300% (Fig 4).

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Fig 4 Relation of diffraction of light with aperture. Fig 5 Depth of field at (a) f/5.6, (b) f/8, (c) f/11(probably the sweet spot of this lens), (d) f/18, and (e) f/32 with a 100-mm macro lens.

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Diffraction of light can occur with an aperture of f/11 or smaller. Most all dental photography will have a high diffraction of light index with a loss of sharpness. However, this loss of sharpness is barely perceivable and it allows us to obtain an acceptable depth of field. To generate the maximum level of sharpness, one should use an f-value no greater than f/11; this is known as the “sweet spot” of the lens. However, this would be unacceptable in clinical dental macro photography due to the poor depth of field at f/11 (Figs 5a to 5e).

5e

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Fig 6a A-point (start point of the scan) in the sample shown in Fig 3 magnified at 5:1, with a depth of field of 0.02 mm (20 µm) in a microscope objective with f/0.25 aperture. Fig 6b B-point (final point of the scan) in the sample shown in Fig 3. Fig 6c Sample after the focus stacking process, made with 481 images. Note the nylon fiber that was not previously visible.

For scientific/nature micro and macro photography, both sharpness and absolute control of the depth of field are essential. While exceeding the laws of optics, both sharpness and control of the depth of field can be achieved by digital photography with the use of specialized software. To generate an image with controlled depth of field, a photographic scanning of the object must be done. The photographic scanning captures a series of different focused areas on different images that will be merged, or stacked, using dedicated software. This is known as the focus

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stacking technique. The focus stacking technique allows the photographer to use any amount of magnification while obtaining full control of the depth of field (Figs 6a to 6c). The main advantages of focus stacking are to (1) develop a perfectly focused image with extraordinary depth of field, (2) create an ultra-sharp image (even if enlarged up to 300%) free of diffraction of light (Figs 7a to 7c), and (3) obtain higher resolution than a sophisticated microscope when a magnifying lens is used (Figs 8a to 8c).

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7a

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Fig 7a Image of palatal side of a maxillary central incisor composed of 485 different images focus stacked using a microscope lens and computer software. Magnification: 5:1. Fig 7b Same image as in Fig 7a enlarged 100%. Note how the details are preserved. Fig 7c Same image as in Fig 7a enlarged 300%. Note the sharpness and richness of the details.

7c

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8a

8b

Fig 8a Focus stacking of maxillary central incisor composed of 493 different images focus stacked using a microscope lens. Magnification: 5:1 (5×) with depth of field of 0.02 mm (20 µm). Fig 8b Focus stacking of posterior fractured zirconia crown composed of 50 stacked images with a 35-mm reversed coupled lens. Magnification 2:1 (2×) with depth of field of 1.5 mm. Fig 8c Focus stacking of an angulated screw composed of 90 stacked images with a 35-mm reversed coupled lens with 52-mm extension tube. Magnification 3:1 (3×) with depth of field of 0.5 mm.

8c

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www.pdflobby.com Focus Stacking Macro Photography: Achieving Ultra-High Resolution and High Magnification in Dentistry

9

10

Fig 9 Camera and 100-mm macro lens with cable connected to a computer with Helicon Remote software. Fig 10 Helicon Remote Software with usual settings on the camera for method A.

FOCUS STACKING METHODS Method A: Static Camera and Focus Scanning with the Lens In this method, the camera and the object remain static on a tripod and stand, and it is necessary to use a lens with a focus ring. A mechanical lens can be used, moving the focus to make a manual scan. Autofocus (electromechanical) can also be used, which will allow connection of the camera (via data cable) to a computer and dedicated software

(Helicon Remote, http://www.heliconsoft.com/heliconsoftproducts/helicon-remote/) (Fig 9). This software controls the process of stacking. It also assists in calculating the number of images needed. For this procedure, the photographer selects the aperture (f-value on sweet spot) and assigns the start and the end points for the photographic scanning process (Fig 10). Method A is applicable for a reproduction range of 1:1. A conventional 105-mm, 100-mm, 85-mm, or 60-mm electromechanical macro lens can be used.

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Fig 11 Nikon D810 DSLR camera with 35-mm inverted lens and Stack Shot device (rail and controller).

Method B: Moving Camera and Lens for Focus Scanning

For method B, there are several options depending on the amount of magnification the photographer needs:

This is the most versatile method, as it allows the use of any type of lens and adaptations to achieve 1:1, 1:5 (5×), 1:10 (10×), or greater magnification. A macro rail is necessary for advancing the camera and lens complex. The rail can be mechanical or electronic. According to the magnification and depth of field of the lens used, the photographer can advance the rail in millimeters or microns (Fig 11).

• 100/105-mm macro lens with extension tubes. • Normal lens (50 mm) with extension tubes. Up to 1:1 can be achieved with an extension of a 50-mm reversed coupled lens. A reproduction of 1:1 can also be achieved with a 50-mm non-macro reversed coupled lens with a special adapter (Nikon BR2 or similar adapter for Canon). A 50-mm extension tube can be added to obtain a reproduction of 2:1. • 35-mm lens reversed coupled (Figs 12a and 12b). Almost 2:1 can be achieved. A 50-mm extension can be added to achieve 3:1. • Specialized lenses: Canon MPE-65 mm (up to 5:1) and Mitakon Zhongyi 20-mm f/2 (up to 4.5:1).

LENSES AND MACRO RAILS For method A, the ideal lens is the 100/105-mm macro lens. A mechanical macro lens with a wide focus wheel is preferable, since it allows a softer and more precise scanning process. A lens controlled electronically is easier to operate using a computer connected to your camera by data cable (USB type) and remote focusing software.

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Mechanical rails are ideal for short-distance scanning (Velbon Super Mag Slider Macro Rail or Kirk SRS-7 Slide Rail System). Electronic macro rails include the Stack Shot, an automated macro rail from Cognisys (Fig 13).

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12a

12b

13

Fig 12a Nikon 35-mm 1.8G lens with BR2 adapter for reverse coupling. Fig 12b Nikon 35-mm 1.8G lens reversed coupled in the camera. Fig 13 Stack Shot macro rail with the controller and shutter cable for camera.

ILLUMINATION Both continuous light and flash are acceptable for focus stacking photography. The only advantage of using continuous light (LED lights) is for modeling and controlling shadows. The disadvantages of continuous light are many:

control of color temperature is complicated, very intense lights must be used so the exposure time is not too prolonged, and a very stable tripod must be used. For flash photography, one can choose from ring flashes, speedlites, or studio lights. Color temperature, light intensity, and exposure time are easily compensated. Tripod

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Fig 14 Usual settings on the camera for method B.

use is also important, but due to the short exposure time and flash synchronization, instability or vibration is more controllable.

Aperture Setting Always use the sweet spot of your lens. The rule to finding that mid-range sweet spot is to count up two full f-stops (aperture settings are called f-stops) from the widest aperture. If the widest aperture of a lens is f/3.5, then two full stops from there would make the sweet spot around f/7.

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Shutter Speed If using continuous light, the shutter speed will depend on the intensity of the illuminator; the camera exposure meter calculates the correct exposure. If using flash, a flash sync speed of 1/125 to 1/250 second is used to synchronize any type of flash.

ISO Range The ISO value compensates for the light intensity. When using flash, it is easier to be within an ideal range of ISO 100 to 400 to avoid digital noise (Fig 14).

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15a

15b

Fig 15a Direct image of a presinterized sample zirconia crown at 1:1 with a 100-mm macro lens on f/22 diaphragm value. Fig 15b Helicon Focus software for stacking 41 images captured with a 35-mm reversed coupled lens.

PROCEDURES Method A with Autofocus Macro Lens 1. Prepare and connect your camera to your computer with focusing software. 2. Adjust the settings: ISO, shutter speed for flash sync, and aperture (always on sweet spot). 3. Adjust the power of the flash and control the exposure. 4. Select the start point A and end point B of the scan; the software will calculate the number of images you need based on the diaphragm value. 5. Start the process.

Method B with Non-Autofocus Macro Lens and Macro Rail 1. Select the lens and the magnification ratio. 2. Adjust the settings: ISO, shutter speed for flash sync, and aperture (always on sweet spot). 3. Adjust the power of the flash; correct the exposure. 4. Select the start point A and end point B of the scan; calculate the number of images you need based on the

depth of field area generated by your diaphragm value and your lens magnification. 5. Set the number of shots on the controller. 6. Start the process.

FOCUS STACKING SOFTWARE Although Adobe Photoshop can stack images, it is not the ideal tool for this job. Specialized software developed exclusively for focus stacking photography is available: Zerene Stacker and Helicon Focus. This author has experimented with multiple software, and Helicon appears to be the simplest and most effective (Figs 15a to 15d). In addition, Helicon has the Helicon Remote to control the lens and camera in case the photographer wants to use method A. In both cases, the process is very simple and requires few steps. After obtaining the images, drag them to the software window: 1. Select the stacking method. 2. Start the process (render button). 3. Save the final image (can be saved in different formats).

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15c

Fig 15c Final result of the process at 3:1 reproduction ratio. Fig 15d Final result at 5:1 reproduction ratio with a microscope lens (444 stacked images).

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15d

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CONCLUSION The focus stacking technique, described herein for the first time specifically for use in dental photography, offers the possibility to achieve images of high magnification with high detail, resolution, and digital amplification up to 300%. Such images can offer great potential for dental educators and other dental professionals who want to learn and explore with simple and affordable equipment.

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Copyright of Quintessence of Dental Technology (QDT) is the property of Quintessence Publishing Company Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

MASTERPIECE

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Full-Mouth Rehabilitation of a Bruxist Patient: A Functional Approach

Mario Alessio Allegri, DDS1 Cristian Marchini, DT2 Allegra Comba, DDS3

Private Practice, Verona, Italy. Dental Technician, Verona, Italy. 3 PhD Student, University of Bologna, Bologna, Italy. 1 2

Correspondence to: Dr Mario Alessio Allegri, Vicolo San Faustino 2, 37129 Verona, Italy. Email: [email protected]

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C

omplete oral rehabilitation requires careful evaluation of the patient to formulate an appropriate and minimally invasive treatment plan. The prognosis for oral rehabilitation is known to rely mainly on control of infection and occlusal forces. However, whereas the diagnosis and treatment of infectious diseases such as caries and periodontitis are always taken into consideration, precise study of occlusal forces is often considered a minor aspect of treatment. Occlusal forces are related closely to bruxism, the only dental function associated with the application of high levels of tangential stress to a resistive unit (ie, a tooth-restoration complex or implant-prosthetic unit).1

Complete rehabilitation also requires precise evaluation of existing restorations in the patient’s mouth. The FDI World Dental Federation criteria are used widely to determine whether reintervention is needed. Initially formulated for operator calibration in clinical studies and for didactic purposes, these criteria can be applied in daily clinical practice to evaluate the biologic risk related to the maintenance of existing restorations.2 This article describes a case that involved consideration of various aspects of reintervention, occlusal force management, and minimally invasive indirect restoration.

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1b

1a

Figs 1a and 1b Initial situation of the patient complaining about poor esthetics of her smile.

Table 1

Evaluation Criteria for Reintervention and the Level of Biologic Risks of Maintenance Obtained Through Literature and Subjective Clinical Experience Low

M/L

M

M/H

H

N/A

Esthetic properties Surface luster

X

Staining Surface Margin

X* X

Color match and translucency

X

Esthetic anatomical form

X

Functional properties Fracture of material and retention

X*

Marginal adaptation

X

Occlusal contour and wear Qualitatively Quantitatively

X* X*

Approximal anatomical form Contact point Contour

X* X*

Radiologic examination (when applicable)

X*

Patient’s view

X

Biologic properties Postoperative (hyper-) sensitivity and tooth vitality

X

Recurrence of caries, erosion, abfraction

X*

Tooth integrity (enamel cracks, tooth fractures)

X*

Periodontal response (always compared to a reference tooth)

X

Adjacent mucosa

X*

Oral and general health

X

L = low; ML = medium/low; M = medium; M/H = medium/high; H = high; N/A = not applicable. *Clinical experience confirmed by evidence-based dentistry.

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2a

2b

Figs 2a to 2c Preoperative intraoral situation. (a, b) The maxillary and mandibular arches showed occlusal wear and inadequate restorations. (c) The Brux Checker showed severe interferences on both the working and balancing sides.

2c

PATIENT PRESENTATION AND DIAGNOSIS A 65-year-old patient complained about the esthetics of her smile and her chewing efficiency at a routine visit (Figs 1a and 1b). The medical anamnesis was negative, and clinical examination revealed several direct and indirect restorations placed about 15 years previously. The existing restorations were evaluated using a modified version of FDI World Dental Federation criteria implemented to determine the biologic risk of their maintenance, with support from data in the literature and clinical experience (Table 1). Intraoral examination revealed that the existing fillings and

crowns were clinically insufficient and did not meet the minimum requirements for their maintenance. The patient’s restored and natural teeth showed wear, with poor margin quality and areas of dentinal exposure. Analysis of the dental surfaces, Brux Checker evaluation, and the anamnestic exclusion of intrinsic factors contributing to this wear (eg, acidic diet, gastroesophageal reflux) led to the diagnosis of sleep bruxism (Figs 2a to 2c). Full-mouth radiography (Fig 3), periodontal charting, and complete photographic documentation were performed. Study casts were made, and Angle Class I relationships of the canines and molars were detected, despite the occlusal surface wear (Figs 4a to 4e).

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3

4a

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4e

4d

Fig 3 Preoperative full-mouth radiographs. Figs 4a to 4e Plaster casts in maximum intercuspation. (a to c) Right lateral, frontal, and left lateral views. (d, e) Lingual views show canine and molar Angle Class I relationships of the left and right sides.

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5c

5b

5a

Figs 5a to 5c Plaster casts mounted in the articulator by means of an individual facebow and intermaxillary keys registered in neuromuscular position.

TREATMENT GOALS

CLINICAL PHASES

The following treatment goals were established with the patient’s agreement:

Phase 1: Evaluation of the Vertical Dimension of Occlusion and Data Collection

• Improvement of smile esthetics • Replacement of old inadequate restorations • Occlusal therapy to improve chewing efficiency and minimize the detrimental effect of bruxism on tooth and joint structures • Minimal removal of sound tissue

To restore the esthetic and functional parameters, the vertical dimension of occlusion (VDO) was evaluated and changed according to the treatment goals. The new VDO was established using the following approaches, as suggested in the literature3: • • • • •

Analysis of pretreatment records (photographs) Evaluation of incisor height Phonetic evaluation Evaluation of mandibular position at rest Assessment of facial appearance with the muscles and other soft tissue at rest

To record the position of the mandible at rest without muscular tension (ie, the neuromuscular relaxation position) and to transfer the VDO obtained clinically to the dental technician, a resin jig was created. Hard-setting silicone indices were created on the posterior teeth to enable the collection of all information needed for mounting the casts in the articulator (Figs 5a to 5c).

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6a

6b

6d

6e

7a

7b

6c

6f

7c

Figs 6a to 6f Occlusal plane setting by means of a dedicated device. (a to c) A 10-degree inclination plane was planned with respect to the axio-orbital plane. (d, e) Individual definition of curve of Spee by means of a dedicated device. (f) Active centric definition: active centric cusps were established in the mandible. Figs 7a to 7c Incisal table and articulator condylar housings setting according to condylography.

Phase 2: Complete Wax-up The plan for restoring functional occlusion was developed using a Slavicek Class I wax-up.4 An individual occlusal plane inclination (OPI) of 10 degrees relative to the axio-orbital plane was calculated according to the following schematic rule: OPI = sagittal condylar inclination (SCI) – disclusion angle (DOA) – cusp inclination (CI) (Figs 6a to 6f).

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The SCI was determined using condylography (Figs 7a to 7c). Protrusion and retrusion curves providing SCI values of 51 degrees and 56 degrees for the right and left jaws, respectively, were selected. The DOA represents the patient’s freedom of sagittal movement, with a higher value indicating a lower risk of occlusal interference. DOAs are usually 8 to 12 degrees. However, as patients with bruxism require larger DOAs, an angle of 10 to 12 degrees was chosen.

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8c

8b

8a

Figs 8a to 8c Sequential guidance system developed, starting from the functional guidance path of the maxillary first molar. Fig 9a Occlusal view of the guidance system of the maxillary first molar. Figs 9b and 9c Wax-up of the functional guidance path of the maxillary first and second premolars. The guidance system was set to allow the anterior tooth to disclose the following one. Fig 9d Occlusal view of the guidance systems of the maxillary first molar and premolars.

9a

9c

The CI is closely related to chewing efficiency, with a higher value indicating greater masticatory efficiency. For the present case, a CI of 30 degrees was planned to provide favorable chewing function. Once the articulator was set, wax-up was performed by the dental technician and a sequential guidance system with canine dominance was developed in harmony with the SCI

9b

9d

to ensure the lack of interference during functional movement and minimal, but efficient, disclusion (Figs 8 to 12). The guidance system was studied to ensure that it guaranteed progressive enrollment of the posterior elements if canine wear occurred. The buccal aspect of the wax-up was then implemented by esthetic evaluation supported by a complete photographic documentation (Figs 13 to 15).

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10b

10a

10c

11b

11a

12a

12b

12c

Fig 10a Protrusive guidance system setting. Figs 10b and 10c Protrusion keys (1 mm and 2 mm) inserted on the articulator. Figs 11a and 11b Protrusive guidance system waxed on the canine according to articulator settings. Figs 12a to 12c Incisal table and laterotrusive guidance path waxed on the canine. Fig 13 Complete sequential guidance system. Figs 14a and 14b Occlusal views of the completed wax-up of the maxillary and the mandibular arches. Figs 15a to 15e Complete wax-up providing an effective guidance system, nice esthetics, and good intercuspation.

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13

14b

14a

15a

15d

15c

15b

15e

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16a

16b

16c

16d

16e

16f

17a

17b

17c

17d

17e

17f

Figs 16a to 16f Comparison of the smile of the patient (a to c) before and (d to f) after a composite resin mock-up validating the esthetic outcome planned with the wax-up. Figs 17a to 17f (a) Increased VDO creating an interocclusal space that is (b, c) filled with no-prep provisional veneers (d to f) luted on the palatal walls.

Phase 3: Validation of Maxillary Arch Esthetics and Function Esthetic validation of the wax-up was performed using a mock-up. A silicone index with high Shore hardness and a

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self-curing composite resin were used for this purpose. No intraoral adjustment was made, as the shape and proportions of the teeth in the wax-up met the patient’s expectations (Figs 16a to 6f).

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18a

18b

18c

18d

18e

18f

Figs 18a to 18d Posterior teeth prepared to receive indirect composite overlays. Figs 18e and 18f The provisional restorations replicated the occlusal design of the wax-up.

Phase 4: Anterior and Posterior Preliminary Preparations No-prep palatal veneering was planned for the maxillary anterior teeth (Figs 17a to 17f). All posterior restorations were removed under rubber dam isolation, and carious lesions were cleansed. When complete detersion of the affected tissue had been achieved, biomechanical evaluation of the residual tooth structure was performed, and cuspal coverage was planned for all posterior elements.5

Endodontic treatments were performed where necessary. An implant was inserted to replace the missing first molar and to allow single-tooth rehabilitation of the third quadrant. Composite buildups were made to restore the lost dentinal cores, and fiber posts were placed where needed to strengthen the tooth-restoration complex considering transversal loads. The posterior teeth were then prepared for provisional restoration, reproducing the occlusal morphology of the wax-up (Figs 18a to 18f).

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18g

18h

18i

18j

19a

19b

19c

Figs 18g to 18j The composite overlays were luted under rubber dam isolation with a multi-step adhesive procedure. Figs 19a and 19b Occlusal view of the provisional restorations luted in the maxilla and mandible. Fig 19c Brux Checker showed improved support and guidance system efficiency with respect to the initial evaluation.

Phase 5: Manufacture and Luting of Provisional Restorations Provisional restorations were made with composite resin, except for the existing full-crown preparations, which received acrylic crowns. All provisional restorations exactly reproduced the new occlusal scheme created with the wax-up. Composite overlays were cemented using a multistep luting procedure, with combined use of a three-step etchand-rinse adhesive system and a preheated composite resin (Figs 18g to 18j). The provisional acrylic crowns were fixed with a eugenol-free temporary cement (Figs 19a to 19c).

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The provisional phase has two main advantages: it enables (1) testing of the therapeutic position and new occlusal scheme and (2) performance of restoration finalization at different times according to the patient’s schedule and needs.1

Phase 6: Occlusal Reevaluation At 1, 3, and 6 months after delivery of the provisional restorations, the masticatory muscles and articular structures were evaluated. A Brux Checker test was also performed at the 6-month follow-up appointment to confirm the clinical effectiveness of the new occlusion.1

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20a

20b

21a

21b

Fig 20a Definitive preparations for full crowns in the maxillary anterior teeth. Fig 20b Controlled and uniform thickness was provided for the restorations. Figs 21a and 21b Thickness control verified intraorally with silicone index obtained from the wax-up.

Phase 7: Definitive Preparations All preparations benefited from the increased VDO in terms of tissue invasiveness. In the anterior region, the need to reprogram the functional palatal surfaces, close the diastemas, and restore the morphology of the buccal surfaces indicated the placement of complete coronal preparations and full crowns. In the posterior area, preparation design followed the princi-

ple of minimal invasiveness and considered the biomechanical requirements of cavity design.5 In the anterior region, accurate thickness was achieved with silicone index guidance; in the posterior region, thickness control was obtained by means of guiding grooves and the preparations were performed with strict reproduction of the anatomical reconstructions from the occlusal wax-up (Figs 20 to 23).

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www.pdflobby.com ALLEGRI ET AL Figs 22a to 22l Silcone indices obtained from the initial casts to evaluate the amount of sound tissue removal. The sagittal slices showed a minimally invasive tooth reduction on both (a to f) the vestibular and (g to l) the palatal sides.

22a

22b

22c

22d

22e

22f

22g

22h

22i

22j

22k

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22l

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23a

23b

23c

23d

23e

23f

Figs 23a to 23f Definitive preparations of the maxillary and mandibular posterior teeth.

24a

24b

24c

24d

24e

24f

Figs 24a to 24f (a to c) Master casts for the manufacturing of lithium disilicate monolithic crowns. The crowns were (d) waxed, (e) heat pressed and carefully adapted on the galvanized model, and (f) stained.

Monolithic lithium disilicate was used for anterior crowns and posterior partial restorations. Zirconia copings with pressed leucite-reinforced feldspathic ceramic veneering

were used for full-crown restorations, including the screwretained implant-supported crown (Figs 24 to 26).

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25a

25b

25c

25d

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25f

25g

25h

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25j

Figs 25a to 25j (a to c) Master casts for the manufacturing of posterior restorations in the maxilla. (d to f) After waxing, (g to j) monolithic lithium disilicate was employed for partial tooth preparations with the press and stain technique, while zirconia copings with pressed leucite-reinforced feldspathic ceramic veneering were used for full-crown restorations.

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26a

26b

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Fig 26a Master cast for the manufacturing of posterior restorations in the mandible. Fig 26b and 26c After waxing, monolithic lithium disilicate was employed for partial tooth preparations with the press and stain technique. Figs 26d to 26k Zirconia copings with pressed leucite-reinforced feldspathic ceramic veneering were used for fullcrown restorations and for the screwretained implant-supported crown.

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27a

27b

Figs 27a and 27b Occlusal views of the definitive restorations in the maxilla and mandible. Fig 27c Brux Checker showed correct support (blue marks recorded with occlusal paper in maximum intercuspation) and an efficient canine guide. Fig 28 Final full-mouth radiographs. Figs 29a and 29b Lateral views of the final treatment outcome. Fig 30a Frontal view of the final situation. Figs 30b and 30c The patient’s smile showed a clear improvement of the esthetics. 27c

Phase 8: Luting The anterior lithium disilicate full crowns and posterior overlays were checked carefully to ensure marginal fit, proper occlusion, and color integration. Luting was performed under rubber dam isolation following a multistep protocol. The tooth surfaces were cleaned and gently sandblasted with aluminum oxide particles. A three-step etch-and-rinse adhesive with 2% chlorhexidine digluconate as an additional primer was used on the dental surfaces. The inner ceramic surfaces of the restorations were acid-etched and treated with silane and bonding. Low-viscosity photocured composite resin was used for anterior crown cementation to guarantee undisturbed seating of the restorations, while preheated high-viscosity photocured composite resin was used to lute the overlays. The zirconia full-crown restorations were luted using a simplified technique: a retraction cord was placed around the tooth in the gingival sulcus, and the abutment surface was sandblasted gently with 50-micron aluminum oxide

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particles. The inner surfaces of the restorations were sandblasted with silica-coated aluminum oxide particles, treated with a specific primer for zirconia containing 10-MDP, and finally a self-adhesive cement was used. Careful occlusal adjustment was performed once the cementation procedures were completed.

Phase 9: Occlusal Reevaluation and Follow-up At the end of treatment, full-mouth radiography, periodontal charting, and complete photographic documentation were performed. Final casts were made, and the patient was evaluated with Brux Checker, which confirmed that satisfactory functional results had been obtained. The results of muscle palpation were good, and the patient confirmed satisfactory chewing efficiency and a pleasant esthetic outcome (Figs 27 to 30).

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28

29b

29a

30a

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DISCUSSION This case report described full-mouth rehabilitation in a patient complaining of poor esthetics and exhibiting severe tooth wear. The treatment conformed to two main criteria: minimal biologic invasiveness and control of occlusal forces. Tooth wear is a common condition that affects the tooth anatomy and causes the loss of mineralized tissue. This condition increases the risks of tooth sensitivity, tooth discoloration, and adverse reactions of the pulp; most importantly, tooth wear leads to the loss of function and poor esthetics. Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear produced through tooth-to-tooth contact), and erosion (dissolution of hard tissue by acidic substances).6 In the case presented here, the tooth wear was associated mainly with attrition, due largely to sleep bruxism. Bruxism is defined as repetitive activity of the jaw muscles characterized by clenching or grinding of the teeth and/or maintenance of the mandible in a fixed position. Bruxism has two distinct circadian manifestations: it can occur during sleep (sleep bruxism) or during wakefulness (awake bruxism).7 In patients with bruxism, the natural teeth and restorations are submitted to abnormal occlusal forces, which may overload the muscles and joint structures and dramatically increase the risk of mechanical failure of a rehabilitation. Some authors have suggested that bruxism is caused or exacerbated by occlusal interference, which supports the need for occlusal treatment to stop or at least reduce it. However, evidence from the literature does not support this point of view.8 Furthermore, whether bruxism should be considered an undesirable habit (or condition) is questionable. According to Slavicek and Sato, bruxism is associated with stress management, a major function of the “masticatory organ.” Following this philosophical perspective, called the cybernetic approach, bruxism should not be treated as a pathologic condition. Instead, it requires accurate examination when planning adequate rehabilitation to control the occlusal forces developed during stress management.9 The moduli and directions of occlusal forces must be evaluated. The design of a restoration can avoid excessive stress concentration on the restorative interfaces and, ultimately, the residual tooth structure. A guiding system designed in harmony with the SCI, together with creation of proper OPI and DOA, may provide the patient with interference-free function and avoid stress concentration on the

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tooth-restoration complex from occlusal loading during bruxism. Once the occlusal forces have been managed, a second factor must be considered to improve rehabilitation longevity: the amount of residual tooth structure. The preservation of an adequate amount of sound tissue is fundamental to the integrity of the tooth-restoration complex, and minimally invasive preparation should always be preferred. In the case described here, minimal invasiveness was made possible by: 1. An increased VDO 2. Guided reduction of wax-up–derived anatomical provisional indirect composites adhesively luted on the remaining tooth structure in the posterior area 3. Guided reduction of the anterior teeth, assisted by silicone indices obtained from the wax-up

CONCLUSION Patients with bruxism requiring prosthetic rehabilitation can be treated successfully when the achievement of stable occlusion and an individual guidance system are planned together with a minimally invasive approach to tooth preparation.

REFERENCES 1. Onodera K, Kawagoe T, Sasaguri K, Protacio-Quismundo C, Sato S. The use of a bruxchecker in the evaluation of different grinding patterns during sleep bruxism. Cranio 2006;24:292–299. 2. Hickel R, Peschke A, Tyas M, et al. FDI World Dental Federation— Clinical criteria for the evaluation of direct and indirect restorations. Update and clinical examples. J Adhes Dent 2010;12:259–272. 3. Abduo J, Lyons K. Clinical considerations for increasing occlusal vertical dimension: A review. Aust Dent J 2012;57:2–10. 4. Slavicek R. The Masticatory Organ. Klosterneuburg, Austria: GAMMA Medizinisch-wissenschaftliche Fortbildungs-GmbH, 2002 (reprinted 2013). 5. Fichera G, Devoto W, Re D. Cavity configurations for indirect partial coverage adhesive-cemented restorations. Quintessence Dent Technol 2006;29:55–67. 6. Jonsgar C, Hordvik PA, Berge ME, Johansson AK, Svensson P, Johansson A. Sleep bruxism in individuals with and without attritiontype tooth wear: An exploratory matched case-control electromyographic study. J Dent 2015;43:1504–1510. 7. Lobbezoo F, Ahlberg J, Glaros AG, et al. Bruxism defined and graded: An international consensus. J Oral Rehabil 2013;40:2–4. 8. Lobbezoo F, Ahlberg J, Manfredini D, Winocur E. Are bruxism and the bite causally related? J Oral Rehabil 2012;29:489–501. 9. Slavicek R, Sato S. Bruxism—A function of the masticatory organ to cope with stress [in German]. Wien Med Wochenschr 2004;154:584– 589.

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Digital Communication in Three Perspectives

Jun Hyouk Shin, DDS, MS

E

sthetics in dentistry is affected by current trends as well as the limitations imposed by the equipment and materials presently available. As CAD/CAM continues to be developed and analog procedures replaced, use of the latest technology will challenge our current esthetic limitations.

Digital Art Dental Clinic, Busan, South Korea. Correspondence to: Dr Jun Hyouk Shin, Digital Art Dental Clinic, 79, Bujeon-ro, Busanjin-gu, Busan, South Korea. Email: [email protected]

Digital fabrication offers advantages from various perspectives. Of particular interest is digital communication. For instance, when utilizing the data provided by an intraoral scanner, communication about the prosthesis can take place between the dentist and dental technician through a software program and then confirmed through the results of accurate digital CAD/CAM crowns. And when using a surgical guide for placing an implant, it is possible to discuss and simulate the ideal implant location before surgery, which will translate to better prosthetic and ultimately better esthetic results. Now, with digital communication directly affecting the integrity of the prosthesis, we have entered a new era for prosthetic and esthetic dentistry. The case presentations in

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this article introduce direct and real digital communication in three perspectives: • Intraoral scan data • Digital CAD/CAM prosthesis fabrication • Digital guided surgery Digital devices are very much a part of our clinical environment today; digital cameras and video recorders, intraoral scanners, and computerized tomography are used

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routinely from the time a patient first steps in our offices and throughout all subsequent treatment phases. We know the importance of using intraoral photographs, facial photographs, and video recordings to achieve the best esthetic results through better communication. Today we also need to include intraoral scan data files in this list. In the patient shown above, for whom laminate veneers were fabricated with a refractory cast process, digital consultation and digital diagnosis were able to provide analysis on the same day for easier and more effective communication of the treatment plan.

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Using conventional methods, we typically consult with our patients after taking an analog impression and using it to make a stone cast and wax-up, as above, which is quite difficult to do on the same day. However, in the digital world, we can easily communicate with our patients regarding their esthetic concerns the same day.

The patient below required two crowns in the esthetic zone. As in the previous patient shown, after consultation with her in regard to the shape, shade, and size of the teeth, a provisional crown could be prepared in advance according to the agreed-upon CAD/CAM design. Once again, this is a good visual communication tool during consultation with the patient to ensure that the patient, dentist, and technician are informed and in agreement.

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My passion for clinical esthetic treatment includes the photo shoot, as shown throughout this article in the cases described. In addition to the camera, I rely heavily on the intraoral scanner. Our digital devices can change our clinical environment, and smart devices now allow us to communicate directly in clinical practice—for instance, in transferring occlusal contact points as shown below.

After intraoral scanning, the occlusal contact points are marked using articulating paper in the patient’s mouth and scanned. This scan can be used for digital CAD virtual mounting. The file shown with the occlusal contacts marked was designed using CAD in the laboratory. With the CAD design we can confirm that the prosthesis is fabricated as intended and that the full zirconia crown is precisely made. With digital software and equipment, the occlusal contact points can be reproduced in the restored tooth, but for best results, clinical considerations—such as occlusion and tooth morphology—must be considered. I typically compare the patient’s actual oral cavity with the intended occlusal contact points as well as tooth shape using helpful applications, such as WhatsApp, Facebook Messenger, KakaoTalk, etc, on a digital device, such as a TV, PC monitor, or smart phone.

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PROVISIONAL PROSTHESIS In esthetic treatment, the provisional prosthesis is particularly important, especially in terms of facial harmony. Cases 1 to 5 present the design and fabrication of provisionals

for different restorative situations with a focus on the digital methods used, which have continued to develop during the treatment of these patients.

Case 1: Maxillary and Mandibular Provisionals

tion and mandibular anterior six-unit fixed partial denture. At the time, intraoral scanners were available only in monocolor. The data of the initial examination could be analyzed and stored through the scanner, so that after treatment, the first visit record was stored permanently in the file without any space or time constraints—a very nice feature.

This patient, a 60-year-old man, was treated from 2013 to 2014 with continual follow-up from that time. The treatment plan included a maxillary full-arch implant reconstruc-

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At the time, CAD/CAM polymethyl methacrylate (PMMA) provisional crowns were fabricated using a traditional impression technique on a stone cast. The maxillary implant rehabilitation was divided into three parts: anterior, right posterior, and left posterior. Customized abutments and full zirconia definitive prostheses were later made with the aid of an intraoral scanner. The implants were titanium-based hybrid screw type.

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Setting the vertical dimension of occlusion was done using a Gothic arch tracer and comparing (using an analog method) current photographs with 20-year-old photographs of the patient when the teeth were healthy. The implants were placed without a digital surgical guide.

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Case 2: Provisional Anterior Crowns This patient, a 30-year-old woman, presented with worn maxillary anterior teeth that required crown restoration. The wax-up and copings were fabricated digitally by double scanning. The diagnostic wax-up could then be designed directly on CAD software with the intraoral scan data. Before teeth preparation, CAD/CAM PMMA provisional crowns were fabricated. The digital provisional crowns

could be used in the preparation guide template to check the proper amount of tooth preparation required and other details. In clinical practice, working only in the mouth can make it difficult to achieve harmony with the patient’s face and lips. Modifications were required for this patient. The modified provisional crowns were copied in the patient’s mouth. The lines were marked directly on the teeth, and the intraoral color scanner was used to scan the marked teeth. The PMMA provisional crowns were made using only the scan data.

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Case 3: Provisional Crown for Single-Implant Restoration Provisional crowns are important for immediate restoration of esthetics and function in implant treatment. They can be fabricated preoperatively (requiring two visits) or postoperatively (requiring only one visit), as in this case. The patient’s maxillary right central incisor was missing when she presented. In a single visit, an implant was placed and immediately scanned intraorally, and the provisional was fabricated.

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CAD/digital tissue sculpting

CAD/mirroring

CAM & milling

The workflow was determined initially, followed by the scanning step immediately after implant surgery and CAD/CAM fabrication of the provisional abutment. At the time (2012), TRIOS (3Shape) was only a monocolor scan system. Implant surgery was completed in 1 hour and the provisional abutment was made and placed in the patient’s mouth all in one visit. The provisional crown was purposely made smaller than the final prosthesis for less tension and a tight seal. The final implant abutment and crown (titanium-based zirconia customized abutment, porcelain layered lithium disilicate crown) were then completed. Viewing the tooth from different angles on the computer monitor is an important aspect of CAD/CAM. The 3D examination of the tooth axis is especially important. The photographs at left are from the patient’s 2-year follow-up appointment.

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Case 4: Surgically Guided SingleImplant Placement In this case, digitally guided implant placement was used to restore a patient’s central incisor. Using CT scans and intraoral scan data, diagnosis and analysis

were done immediately, and the digital provisional crown was prepared before tooth extraction and implantation. Implant placement was simplified using digital guidance as planned in advance. This digital workflow can make our clinical procedures easier and more precise, and the result is good for both dentist and patient.

Provisional Stock Abutment Digital Workflow The PMMA provisional crown above was made of a stock abutment base produced from a digital library. “Library” refers to a 3D drawing for manufacturing. Working with the library directly to the stock abutment can give a detailed and accurate result. Usually stock abutments have a well-managed tolerance of 0 to 5 microns. Library and actual abutments are essentially the same. Given this, a library can offer a great advantage.

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With the library, we do not need to take an impression of the margin, which is nicely subgingival. We do not need to place gingival cord in the margin or worry if the margin is invisible. Regardless of the incomplete impression data, we can make a precision restoration using the library merge on the computer.

Although this stock abutment’s margin is invisible and the scan state is poor, the crown can be fabricated accurately. This zirconia screw-type implant crown stock abutment was made by merging the digital library with intraoral scan data.

Using the digital workflow with the stock abutment library, this precise result was possible.

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Case 5: Provisional Maxillary FullArch Implant Rehabilitation

(one visit) was shown in Case 3. In Case 5, the fabrication method for full-arch implant provisional crowns in advance of surgery (two visits) is described.

CAD/CAM digital fabrication of an implant provisional abutment with production immediately after surgery

To obtain the jaw relation/vertical dimension digitally, the proper vertical dimension was first set by using the digital Gothic arch tracer. Light-body rubber impression material was applied accurately to the inner edentulous surface for good fixation in the mouth. To prevent radiation artifacts, a metal plate was not used in the palate area in this case; instead, alumina markers that are visible on cone beam computed tomography (CBCT) scans were attached, and the CBCT was taken.

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Next, the inner impression of the tracer including the markers was scanned using an intraoral scanner. This was merged with the CBCT image. Then by converting the scanned image, the intraoral situation for implant planning is reproduced in 3D.

This method can also be used for the 3D-printed resin base wax rim.

It can be used with the patient’s original denture or provisional prosthesis as well.

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Sagittal and coronal section views of edentulous state without the resin base denture.

Sagittal and coronal section views of edentulous state wearing only the resin base denture. It is difficult to distinguish between soft tissue and the resin denture. Because of the radiolucent empty space, it is sometimes difficult to know if the denture is placed accurately in the patient’s mouth.

The inner surface of the denture filled with light-body impression material, which can be distinguished well from the radiolucent empty space between the soft tissue and resin base, as it is slightly more radiopaque. When taking the patient’s CBCT, resin denture fit is easily verified.

If there is a radiolucent empty space, as shown above, it can indicate that the denture is unstable in the patient’s mouth. Through the digital inner impression technique and the Gothic arch tracer, the wax rim and denture can be fitted more accurately when taking the CBCT, and the fit of the denture in the patient’s mouth can immediately be easily determined.

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Implant placement was planned using the 3D image containing the jaw relationship, edentulous soft tissue surface, and CBCT information. At the same time, various facial photographs of the patient are helpful for the treatment plan. In planning the ideal implant position, it is necessary to set the tooth position after determining the proper vertical and horizontal relations of the patient’s face.

After the implant treatment plan was evaluated from various perspectives, the digital surgical guide was designed by Implant Studio CAD software (3Shape).

At the same time, the digital provisional crowns were designed by dental CAD software. In this case, the shape of the provisional prosthesis, which would be placed immediately after surgery, needed to be different from the shape of the final prosthesis. The neck portion of the provisional crowns had to be narrow for a good primary closure, with no pressure on the surrounding tissue.

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The digital guide stent was made through 3D printing and the PMMA provisional prostheses through milling, using only the scanned 3D data file. They were ready before the surgery took place.

A benign cyst in the central incisor area can be seen on the CBCT scan. Bone trimming and graft procedure would be necessary. This was already discussed with the patient during the initial visit. Because the patient was apprehensive about having implant surgery, eight implants were placed with flapless surgery for functional and esthetic recovery as soon as possible. It was then planned to remove the cyst and perform the bone surgery with an open flap and place an additional single implant.

Postsurgery photographs taken the same day as surgery. In approximately 1 hour, the patient went from being edentulous to having maxillary full-mouth implants and a provisional prosthesis placed.

Photographs 1 day postsurgery. The patient was not swollen at all and was very pleased to have a full set of teeth. Although nervous before surgery, the patient was thrilled with the result and feeling very confident.

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After 1 month, the second surgery took place to remove the cyst along with bone trimming and grafting. An additional implant was placed in the central incisor area with the previous digital surgical guide stent. At this time, by opening the flap, it could be confirmed that the implants were placed in the proper position as planned. Without the stent, this would have been difficult to achieve.

Ten days after the second surgery; the patient continued to use the existing PMMA provisional prosthesis.

CBCT scans and panoramic radiograph taken 3 months after initial digital guided implant surgery.

This provisional implant prosthesis incorporated many digital technologies: merging of intraoral scanning and CBCT images, 3D printing, guided implant surgery, and CAD/CAM milling. Despite this being my first digitally guided surgery, the results were acceptable, especially given that this was a provisional prosthesis.

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An old photograph of the patient, when her teeth were healthy, was used to confirm the harmony of the vertical dimension and face. The harmony of expression with the provisional prosthesis is captured in photographs at various angles.

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DEFINITVE PROSTHESIS Case 1—Revisited (Final Restoration) The definitive restoration procedure for the patient presented in Case 1 also incorporated the digital perspectives

presented in this article. The definitive mandibular six-unit fixed partial denture was fabricated from the CAD/CAM PMMA provisional prosthesis. The teeth and gingiva were scanned with an intraoral scanner, and the prosthesis was produced using these data only.

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The mandibular six-unit fixed partial denture was CAD/ CAM produced in full zirconia. The full zirconia technique has undergone rapid development in the last few years. For the maxillary full-arch reconstruction, customized abutments were fabricated. After scanning the entire maxilla, the occlusal bite scan was obtained in two parts.

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Because only the visible parts are scanned, even if a crown is fitted in another part of the mouth, it does not appear in the scanned picture; only the scan body and antagonist appear. The customized abutments (titanium-based hybrid zirconia) were applied and then each of the three parts was scanned to produce the final prosthesis.

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The maxillary full-mouth prosthesis was fabricated by intraoral scanner only—no wax-up or porcelain layering. Digital CT-guided surgery was not used in this patient; implants were placed in the traditional manner without a stent. However, I now use digital guided surgery, as was shown in Case 3, routinely for full-mouth implant restora-

tions. Likewise, analog methods were used for jaw relationship and vertical dimension to fabricate the ideal prosthesis in harmony with the patient’s face. As shown in previous cases, I now use the digital Gothic arch tracer and CBCT merging for more direct and easy access.

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At a later follow-up appointment, an intraoral scanner could be used on the gingival surface being maintained by the prosthesis. Through this, the proper relationship of the prosthesis and gingiva could be observed in 3D from various angles. The data could be saved and used later for reference, another great advantage of the digital scanner. With the abutments removed, the intraoral scanner provided a digital impression immediately, which is useful to

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determine the proper emergence profile and crown contour. To make an ideal prosthesis requires close communication between dentist and dental technician. Using remote control software on a mobile device, direct communication among dentists, dental technicians, and the manufacturing centers can take place in real time without limitation no matter where they are located.

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At the 8-month follow-up, the implant prosthesis was removed and the soft tissue profile and full zirconia prosthesis were scanned. With the CAD software it could be observed that function was stable and the appropriate gin-

gival form maintained the tight seal. The papilla height could be measured and the emergence profile and soft tissue profile viewed in cross-section from various views.

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DIGITAL COMMUNICATION Intraoral scan data Digital CAD/CAM Prosthesis (PMMA provisional crown, full zirconia crown) Digital guided surgery

CONCLUSION Indeed, the continuous developments in digital dentistry have made our clinical research and procedures more convenient. However, regardless of the convenience and automation provided by the new technology, we must remain faithful to our long-held values and must preserve and respect the fundamentals laid by our senior scholars. Nonetheless, the continuous advancements in dentistry have enabled us to set higher goals. With exposure to more information in terms of what is possible, through the

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Internet and social media, both dental professionals and patients have higher expectations. Because of this, dentists and dental technicians require a great deal of study to keep up with the new technology and more adept skills to apply the technology in clinical and laboratory practice. Digital technology allows us to achieve more elaborate analysis and results, better communication for patient consultation, more accuracy in prosthetic processes, and more objective implant surgery precision. All this is possible through digital communication in the three perspectives presented throughout this article.

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BIBLIOGRAPHY Anh JW, Park JM, Chun YS, Kim MA, Kim MJ. A comparison on the precision of three-dimensional images acquired by two different digital intraoral scanners : Effects of tooth irregularity and scanning direction. Korean J Orthod 2016;46:3–12. Fasbinder DJ. Computerized technology for restorative dentistry. Am J Dent 2013;26:115–120. Ferencz J, Fanetti P. Enhanced communication: An open dialogue between the dentist and ceramist offered this patient an esthetic and functional solution to teeth discolored by bonded orthodontia. Inside Dental Technol 2011;2:44–50. Guess PC, Att W, Strub JR. Zirconia in fixed implant prosthodontics. Clin Implant Dent Relat Res 2012;14:633–645. Malament KA. The interdisciplinary relationship between prosthodontics and dental technology. Int J Prosthodont 2010;23:134–140. Marinello CP, Meyenberg KH, Zitzmann N, Lüthy H, Soom U, Imoberdorf M. Single-tooth replacement: Some clinical aspects. J Esthet Dent 1997;9:169–178. Mörmann WH, Brandestini M, Lutz F, Barbakow F. Chairside computeraided direct ceramic inlays. Quintessence Int 1989;20:329–339.

Mütherties K, Körner G, Minami T. Art Oral: Non Invasiv, Minimal Invasiv, Invasiv [in German]. Berlin: Quintessenz, 2011. Park JM, Yi TK, Jung JK, Kim Y, Park EJ, Han CH, Koak JY, Kim SK, Heo SJ. Accuracy of 5-axis precision milling for guided surgical template. J Korean Acad Prosthodont 2010;48:294–300. Park JM, Yi TK, Koak JY, Kim SK, Park EJ, Heo SJ. Comparison of fiveaxis milling and rapid prototyping for implant surgical templates. Int J Oral Maxillofac Implants 2014;29:374–383. Scherer U, Stoetzer M, Ruecker M, Gellrich NC, von See C. Templateguided vs. non-guided drilling in site preparation of dental implants. Clin Oral Investig 2015;19:1339–1356. Sun Y, Lü P, Wang Y. Study on CAD&RP for removable complete denture. Comput Methods Programs Biomed 2009;93:266–272. Williams RJ, Bibb R, Eggbeer D. CAD/CAM in the fabrication of removable partial denture frameworks: A virtual method of surveying 3D scanned dental casts. Quint J Dent Technol 2004;2:268–276. Yamazaki M. Esthetic Classifications: Management of Difficult Esthetic Prosthetic Treatment. Tokyo: Quintessence, 2009.

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Yusuke Ninomiya, DDS1 Takayuki Kobayashi, RDT2 Luiz Narciso Baratieri, DDS, MS, PhD3

Nino Dental Office, Tokyo, Japan. Felicita Dental Lab, Kanagawa, Japan. 3 Professor, Department of Dentistry, Federal University of Santa Catarina, Florianópolis, Brazil. 1 2

Correspondence to: Dr Yusuke Ninomiya, Elixir Omotesando, 4-17-16 Jingumae, Shibuya-ku, Tokyo, 150-0001, Japan. Email: [email protected]

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Reconstruction of the Morphology of Teeth Damaged by Wear Using Adhesive Technology

QDT 2018

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2

1

Fig 1 Facial view at the first visit. Fig 2 Condition of the anterior teeth was the patient’s chief complaint.

I

n recent years there has been an increase in the number of patients with tooth erosion reported internationally.1–3 Tooth wear is one of the symptoms of tooth erosion. Tooth wear occurs 10 times faster in patients suffering from tooth erosion—especially on the palatal side, which can lead to more serious problems.4 The risk of tooth loss is higher and the therapeutic intervention more complicated as tooth wear progresses. Therefore, early dental therapeutic intervention is required along with treatment of the cause of the tooth erosion. Exposed dentin after the loss of enamel causes further symptoms. Symptoms induced by tooth wear include loss of tooth morphology, hypersensitivity, and pain. It is reported that 60% of patients with tooth wear complain about esthetics as well.5 For patients with tooth wear, aggressive tooth reduction used to be an inevitable part of treatment, along with crown lengthening and root canal therapy, to increase retention of the prosthesis.6 The risk of losing teeth increases as the treatment becomes more involved.7–9 Recent progress in adhesive technology and dental materials has overcome some of the limitations of conventional mechanical retention of the prosthesis. Enamel is preserved as much as possible when adhesives are used for direct restoration with composite resin or indirect restoration with ceramic compared to full-coverage restorations,

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such as porcelain-fused to-metal crowns, which require conventional circumferential tooth reduction. In the following case, minimally invasive restorative treatment using adhesive technology was carried out to improve esthetics and function in a patient with tooth wear.

CASE PRESENTATION Diagnosis The patient was a female in her twenties. Esthetics and hypersensitivity were her chief complaints (Fig 1). Circumferential enamel loss and multiple caries lesions were apparent. The periodontal condition was within normal limits. The patient was not happy with the color of her teeth, which was affected by the transmitted color of the dentin due to the lack of enamel. She had tried whitening procedures multiple times, but they did not provide a satisfactory result (Fig 2). Overall, the teeth were in good alignment. The anatomical shape of the teeth was lost due to lack of enamel. Tooth wear on the palatal aspect was more apparent, especially on the maxillary anterior teeth. The rough surfaces of the existing restorations in the posterior area were evident (Figs 3a to 3d).

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3a

3b

3c

3d

4b

4a

4c

4d

Figs 3a to 3d Occlusal views of (a) maxillary anterior teeth, (b) maxillary right posterior teeth, (c) maxillary left posterior teeth, (d) maxillary arch. Figs 4a to 4d (a) Occlusal view of mandibular arch, (b) frontal view of mandibular anterior teeth, and (c and d) occlusal views of mandibular right and left posterior teeth, respectfully.

The anatomy of the occlusal surfaces of the teeth was lost and some dentin exposed. The restorations appeared as though they were hanging in the oral cavity due to excessive wear. Diastemas and pathway wear were apparent in the mandibular anterior teeth. Caries lesions on the proximal surfaces were also evident (Figs 4a to 4d).

Treatment Planning and Treatment Phase The first step was to evaluate and determine the position of the maxillary central incisors in relation to the face. It was not necessary to do a full-arch wax-up at this point, since

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5

6

Fig 5 Mock-up of maxillary anterior teeth. Fig 6 Facial view with the mock-up. Fig 7a Casts mounted on the articulator with facebow transfer. Figs 7b to 7g Condition of tooth wear is checked on the casts.

7a

7b

7c

7d

7e

7f

7g

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8a

8b

Figs 8a and 8b Occlusal views of maxillary and mandibular diagnostic wax-ups. Fig 8c Diagnostic wax-up in occlusion.

8c

the patient had not yet accepted the treatment. The maxillary anterior teeth were waxed up for evaluation, since this area was the patient’s main concern (Figs 5 and 6).10 Elongation of the teeth in an apical direction sometimes is required in addition to simple coronal repositioning of the incisal edge due to altered passive eruption. Apical repositioning of the gingiva, orthodontic intrusion, or a combination of these treatments is sometimes indicated. Once the patient agreed to the treatment plan, occlusal diagnosis was made for functional analysis with the casts mounted on the articulator in centric relation with facebow transfer (Figs 7a to 7g). A prominent curve of Spee was observed on the models. Tooth wear was more extensive in the maxilla than the mandible. Characteristics of tooth erosion were seen on both the labial and palatal sides of the maxillary anterior teeth. Loss of tooth structure does not necessarily indicate loss of vertical dimension of occlusion (VDO). However, space for restorative material is secured by increasing the VDO, minimizing the amount of tooth reduction.11,12

There are various theories regarding increasing VDO. Dawson stated that VDO is determined by muscle, which maintains the same length.13 Hence, VDO tends to return to the original height after it is increased due to intrusion of the teeth by muscle activity. Other reports have shown no clinical issues as a result of increasing the VDO up to 5 mm as long as there is no problem in the temporomandibular joints.14–17 If an increase of the VDO is indicated, the new position should undergo functional evaluation for a certain period. VDO is evaluated by a combination of factors, such as facial appearance, phonetics, swallowing, and freeway space.18–21 In this case, the VDO was increased minimally just to restore the original shape of the crown lost by wear.22,23 A diagnostic wax-up was made at the increased VDO, preserving enamel as much as possible (Figs 8a to 8c). Yellow wax was used directly on the cast for mock-up. Provisional mock-ups of the maxillary and mandibular posterior area were fabricated by CAD/CAM (Shofu) of polymethyl methacrylate (PMMA) (Figs 9a to 9f). PMMA

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9b

9a

9c

9d

9f

9e

Fig 9a Designing of posterior mock-up. Figs 9b to 9f Completed mock-ups.

was chosen because of its superior strength and wear resistance compared to conventional self-cure acrylic resin (103 MPa for PMMA; 78 MPa for conventional acrylic resin). The provisional restoration material needs to be strong enough to sustain molar occlusion and be resistant to wear due to parafunctional activity such as bruxism. The posterior provisional mock-up was inserted with no tooth preparation (Figs 10a and 10b). Space for restorative material was created in the anterior area. The condition with both posterior and anterior mock-ups inserted compared to the original condition is shown in Figs 10c and 10d.

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Shown two months after the mock-ups were inserted, the patient was very satisfied with her smile (Fig 11a). The relationship between the central incisors and upper lip was well harmonized (Fig 11b). Since all of the patient’s concerns were resolved after reevaluation of esthetics and function, the treatment continued. First, 0.5-mm pilot grooves were made through the mock-ups (Figs 12a and 12b). Enamel was preserved in the majority of the prepared surfaces. Preservation of as much marginal ridge as possible is important as well.

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10a

10b

10c

10d

Fig 10a Frontal view with posterior mock-up in place. Fig 10b Space for restorative material was created. Figs 10c and 10d Views before and after insertion of anterior mock-up. Fig 11a Two months after insertion of mock-ups. Fig 11b Relationship between central incisors and upper lip.

11b

11a

12a

12b

Fig 12a Pilot grooves are made through the mock-ups. Fig 12b After preparation is completed.

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Fig 13 Completed thin occlusal veneers.

14a

14b

Fig 14a Pilot grooves made as depth guides. Figs 14b and 14c Frontal and occlusal views after completion of preparation.

14c

The completed occlusal veneers are shown in Fig 13. The very thin restorations were fabricated of lithium disilicate.24 The posterior occlusion was established first by bonding the posterior restorations sequentially. The anterior teeth were then restored. Preparation of the anterior teeth was initiated through the mock-ups, same as in the posterior teeth (Figs 14a to 14c).25 The marginal ridge area should be preserved as much as possible, as recommended by Vailati and Belser and others, using the sandwich technique.8,26–31 In this case, circumferential veneer preparation

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was done due to the existence of caries lesions and composite resin restoration in the proximal area. Reduction of the palatal aspect was kept to a minimum, removing undercuts only. The posterior teeth were restored with monolithic lithium disilicate for strength with external staining. The layering technique was used for the maxillary anterior teeth for esthetic reasons (Figs 15a to 15g). Layering was done only on the facial surface to maintain strength. The rest of the dentition was restored using a conventional impression technique and cementation of restorations (Figs 16 and 17).

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15e

15a to d

15f

Figs 15a to 15d Maxillary anterior restorations layered for strength. Figs 15e and 15f Completed restorations on the master cast. Fig 15g Monolithic mandibular restorations.

15g

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16a

16b

16c

16d

17a

17b

Figs 16a and 16b Maxillary occlusal views before and after treatment. Figs 16c and 16d Mandibular occlusal views before and after treatment. Figs 17a and 17b Frontal views before and after treatment.

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18a

18b

18c

Figs 18a to 18c Facial view after the treatment is completed. Well-harmonized smile is achieved.

The patient was very happy with the result, which resolved all of her original concerns. It is clear from her facial expression that the treatment improved not only her intraoral condition but her overall well-being (Figs 18a to 18c).

CONCLUSION Recent progress in dental adhesive technology enables the dentist to provide patients more conservative treatment, effectively solving their patients’ problems and improving

their oral health. While dentistry has taken advantage of the benefits of CAD/CAM technology and its progress has been remarkable, digital technology cannot evaluate the oral condition or make adjustments to restorations. Needless to say, human intervention is necessary, with the dentist being the one who ultimately makes the diagnoses, evaluations, and decisions. Integration of analog and digital technology is inevitable. In general, preserving more tooth structure provides a better treatment prognosis than the conventional approach. It is also beneficial for the patient, who will have more options available for future treatment if it is indicated.

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ACKNOWLEDGMENTS Dr Ninomiya takes this opportunity to express his sincere appreciation to Dr Luiz Narciso Baratieri, Dr Kazutoshi Sakaki, and Dr Shohei Terasawa for their continuous support.

REFERENCES 1. Bardsley PF. The evolution of tooth wear indices. Clin Oral Investing 2008;12(suppl):s15–s19. 2. Van’t Spijker A, Rodriguez JM, Kreulen CM, Bronkhorst EM, Bartlett DW, Creugers NH. Prevalence of tooth wear in adults. Int J Prosthodont 2009;22:35–42. 3. Lussi A, Jaeggi T. Erosion—Diagnosis and risk factors. Clin Oral Investing 2008;12(suppl):s5–s13. 4. Bartlett DW, Blunt L, Smith BGN. Measurement of tooth wear in patients with palatal erosions. Br Dent J 1997;182:179–184. 5. Wazani BE, Dodd MN, Milosevic A. The signs and symptoms of tooth wear in a referred group of patients. Br Dent J 2012;213:e10. 6. Azzopardi A, Bartlett DW, Watson TF, Sherriff M. The measurement and presentation of erosion and abration. J Dent 2001;29:395–400. 7. Lavigne GJ, Khoury S, Abe S, Yamaguchi T, Raphael K. Bruxism physiology and pathology: An overview for clinicians. J Oral Rehabil 2008; 35:476–494. 8. Vailati F, Belser UC. Classification and treatment of the anterior maxillary dentition affected by dental erosion. Int J Periodontics Restorative Dent 2010;30:559–571. 9. Dietschi D, Argente A. A comprehensive and conservative approach for the restoration of abration and erosion. Part I: Concepts and clinical rationale for early intervention using adhesive techniques. Eur J Esthet Dent 2011;6:20–33. 10. Spear FM, Kokich VG, Mathews DP. Interdisciplinary management of anterior dental esthetics. J Am Dent Assoc 2006;137:160–169. 11. Sicher H. The biology of attrition. Oral Surg Oral Med Oral Pathol 1953;6:406–412. 12. Berry DC, Poole DF. Attrition: Possible mechanisms of compensation. J Oral Rehabil 1976;3:201–206. 13. Dawson PE. Evaluation, Diagnosis and Treatment of Occlusal Problems, ed 2. St Louis: Mosby Elsevier, 1989. 14. Turner KA, Missirlian DM. Restoration of the extremely worn dentition. J Prosthetic Dent 1984;52:467–474. 15. Walther W. Determinants of a healthy aging dentition: Maximum number of bilateral centric stops and optimum vertical dimension of occlusion. Int J Prosthodont 2003;16(suppl):s77–s79.

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16. Carlsson GE, Ingervall B, Kocak G. Effect of increasing vertical dimension on the masticatory system in subjects with natural teeth. J Prosthet Dent 1979;41:284–289. 17. Kohno S, Bando E. Functional adaptation of masticatory muscles as a result of large increase in the vertical occlusion [in German]. Dtsch Zahnarztl Z 1983;38:759–764. 18. Hammond RJ, Beder OE. Increased vertical dimension and speech articulation errors. J Prosthet Dent 1984;52:401–406. 19. Gross MD, Ormianer Z. A preliminary study on the effect of occlusal vertical dimension increase on mandibular postural rest position. Int J Prosthodont 1994;7:216–226. 20. Abduo J. Safety of increasing vertical dimension of occlusion: A systematic review. Quintessence Int 2012;43:369–380. 21. Spear F, Kinzer G. Approaches to vertical dimension. In: Cohen M (ed). Interdisciplinary Treatment Planning: Principles, Design, Implementation. Chicago: Quintessence, 2008:249–281. 22. Johansson A, Johansson AK, Omar R, Carlsson GE. Rehabilitation of the worn dentition. J Oral Rehabil 2008;35:548–566. 23. Kois JC, Phillips KM. Occlusal vertical dimension: Alteration concerns. Compend Contin Educ Dent 1997;12:1169–1174, 1176–1177. 24. Magne P, Knezevic A. Simulated fatigue resistance of composite resin versus porcelain CAD/CAM overlay restorations on endodontically treated molars. Quintessence Int 2009;40:125–133. 25. Gurel G, Yerusalmi BM, Shayder A. Monolithic CAD/CAM porcelain laminate veneers with external staining. Quintessence Dent Technol 2013;36:174–182. 26. Magne P, Magne B, Belser UC. Adhesion restorations, centric relation, and the Dahl principle: Minimally invasive approaches to localized anterior tooth erosion. Eur J Esthet Dent 2007;2:260–273. 27. Fradeani M, Barducci G, Bacherini L, Brennan M. Esthetic rehabilitation of a severely worn dentition with minimally invasive prosthetic procedure (MIPP). Int J Periodontics Restorative Dent 2012;32:135– 147. 28. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. Part 1. Eur J Esthet Dent 2008;1:30–44. 29. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. Part 2. Eur J Esthet Dent 2008;2:128–146. 30. Vailati F, Belser UC. Full-mouth adhesive rehabilitation of a severely eroded dentition: The three-step technique. Part 3. Eur J Esthet Dent 2008;3:236–257. 31. Vailati F, Belser UC. Palatal and facial veneers to treat severe dental erosion: A case report following the three-step technique and the sandwich approach. Eur J Esthet Dent 2011;3:268–277.

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Clinical Applications of Ultra-Translucent Zirconia Crowns

M Kazunobu Yamada Cusp Dental Supply Kanare Technical Center 2-1319, Umegaoka Tenpaku-ku, Nagoya-shi Aichi, Japan Email: [email protected]

etal ceramics, long established in the field of esthetic dental restorations, have seen an annual reduction in market size, whereas zirconia ceramics have shown high growth rates. Using a CAD/ CAM system, layered porcelain is applied to the zirconia crown and reproduces the esthetic properties similar to natural teeth. Clinical cases have shown that zirconia resists bending and maintains strength. Recent innovations include the availability of colors—from white to specific matching shades—and high translucency. The recently developed ultra-translucent multilayered Katana Zirconia UTML series and STML series (Kuraray Noritake Dental Inc) have a translucency higher than that of the company’s previous series. It is now possible to achieve esthetically pleasing full-contour zirconia crowns without porcelain layering. Also, since the gradation is built into the disk, color from dentin to the enamel, from a dark color tone to a light tone, shade irregularity is less noticeable. This article describes the properties of these materials, recommendations for usage, and clinically appropriate stain techniques.

QDT 2018

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www.pdflobby.com YAMADA Fig 1 Third-generation Katana Zirconia UTML and STML series (Kuraray Noritake Dental Inc).

HISTORY OF ZIRCONIA IN DENTISTRY Zirconia offers the following benefits for application in esthetic dental restorations: • It is a light and durable material. • It transmits light and there is no black line margin. • It has excellent biocompatibility and is noncorrosive in the oral cavity. • It prevents dental plaque buildup. These benefits rapidly resonated in the market amid the backdrop of a surge in metal prices. Originally when zirconia appeared, the high flexural strength material (with an average high value of 1,100 MPa) was commonly referred to as “white metal.” It was also utilized for full-mouth prostheses and considered “first-generation” zirconia. In some zirconia materials that emphasized strength, alumina was introduced as an additive element. Others sacrificed translucency, which was the original advantage of all-ceramic materials. Because of concern for low-temperature degradation, it was recommended to layer with porcelain and minimize the exposed surface layer of the zirconia material. Thereafter, “second-generation” zirconia appeared, offering improved light-transmitting properties without significantly lower bending strength. High light transmission is particularly advantageous for porcelain layering, as it allows for less reduction of anterior prostheses on the labial side because there is no potential abutment discoloration. The use of full-contour zirconia restorations without porcelain layering increased in posterior teeth. Although it was not esthetically ideal, this expanded the application range to create strong “white” crowns.

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In recent years, “third-generation” zirconia, developed for improved translucency, has been drawing considerable attention (Fig 1). This zirconia material is stabilized in its cubic crystal state, which is reduced in tetragonal form, and is resistant to low-temperature degradation. However, in terms of flexural strength and propagation of cracks, it is necessary to pay attention to fabrication handling and sintering specifics in order to achieve proper transformation to the cubic crystal state. Third-generation zirconia offers ultra-high translucency versus just high light transmittance.

CHARACTERISTICS OF ULTRATRANSLUCENT MULTILAYERED ZIRCONIA Due to patients’ growing dental knowledge and promotion of the 80/20 movement in the dental industry,1,2 the use of prostheses with multiple tooth splints is decreasing. Therefore, new materials suitable for single-tooth restorations or short-span prostheses that exhibit excellent chipping resistance are becoming more desirable and more readily utilized. Figures 2a and 2b compare the transmittance of light in a sample slice (thickness 0.8 mm) of the Katana STML series and the company’s layering porcelain Cerabien ZR (CZR) for veneering to zirconia. Although to the naked eye the STML series is somewhat lower in translucency than the body porcelain, it does have translucency similar to the enamel and mimics the color with a slight gray; this is equivalent to the enamel part of the crown. The STML series shows excellent characteristics as a single monolithic material.

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www.pdflobby.com Clinical Applications of Ultra-Translucent Zirconia Crowns

CZR Opacious Body

CZR Body

Katana Zirconia STML CZR Enamel

CZR Opacious Body

Katana Zirconia STML CZR Enamel

CZR Body

2b

2a

Lithium disilicate glass-ceramic

Katana Zirconia KT Zirconia A

Katana Zirconia UTML

Katana Zirconia ML Katana Zirconia STML

Zirconia B Katana Zirconia STML

Zirconia E

Zirconia C

Zirconia D

Zirconia D

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Katana Zirconia UTML Lithium disilicate glass-ceramic

Zirconia B 0.0

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6.0

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Figs 2a and 2b Comparison of light transmittance in samples (0.8 mm thick) of Katana STML and CZR layering porcelain.

Katana Zirconia KT

Fig 3 Fracture toughness comparison. Measurement condition: indentation fracture (IF) method; weight, 20 kg. Fig 4 Translucency comparison. Measurement condition: light source, D65/2; sample thickness, 0.5 mm. Fig 5 Flexural strength comparison. Measurement condition: according to ISO 6872:2008 (three-point bending test); distance, 30 mm; sample size, 40 × 4 × 3 mm.

Katana Zirconia ML

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Katana Zirconia UTML Lithium disilicate glass-ceramic

0

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5

Figure 3 compares the fracture toughness (in MPa) of a single ceramic material (monolithic). The higher the toughness value, the greater the chipping resistance. Zirconia strength varies depending on the generation in which it appeared. For Kuraray Noritake Dental zirconia, the first KT series has the highest nominal strength. In terms of perceived appearance, the UTML series is highest in terms of translucency (Fig 4) while inferior in terms of its toughness value; however, it shows a value equal to

or higher than that of the lithium disilicate glass-ceramics. Also, the flexural strength (Fig 5) is only half that of the first- and second-generation zirconia. Therefore, clinically applying the STML series and UTML series to long-span fixed partial dentures or prostheses in which crown length is insufficient would not be recommended. Figures 6a to 6c show a comparison of the shade, value, and translucency of the three generations of zirconia in the same mouth. In order to compare the appear-

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www.pdflobby.com YAMADA Figs 6a to 6c Comparison of shade, value, and translucency of (a) firstgeneration, (b) second-generation, and (c) third-generation zirconia with no staining in the same patient’s mouth. Fig 6d Third-generation STML series zirconia with staining shows more harmonized appearance in the mouth. 6a

6b

6c

6d

ance of the zirconia materials, each crown finished with hand polishing was tested (water was used on the inner surface of the crown) without any staining. With the KT series (first generation), HT and ML series (second generation), then STML series (third generation), the appearance is harmonized in the mouth. Figure 6d shows the postoperative condition in which the STML series is stained, exhibiting an even more harmonized appearance with the natural teeth. In addition, a clinical report states that abrasive wear of the opposing natural molar occlusal surface is not influenced by a highly polished zirconia surface3; therefore, the use of staining and glazing to finish should be limited.

APPLICATION OF ULTRATRANSLUCENT MULTILAYERED ZIRCONIA Katana multilayered zirconia disks are structured with four uniquely different layers of color and translucent zirconia powders, but since each interface is blended there is a very natural gradation (Fig 7). In addition to the 16 Vita Classical A1–D4 shades (Vita Zahnfabrik), the UTML series includes 4 enamel shades with less dentin chroma: EA1, EA2, EA3, and ENW. For detailed internal staining with no negative influence from the dentin coloring, the enamel shades should be used. The STML series has a total of 14

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shades consisting of A1, A2, A3, A3.5, A4, B1, B2, B3, C1, C2, C3, D2, D3, and NW (bleaching shade). Taking advantage of these esthetic multilayered zirconia disks is simple and straightforward. One simply selects the disk that corresponds to the restoration shade requested and mills according to the specified CAD/CAM system instructions; an outsourcing CAD/CAM production center can also be asked to produce it. Since the color tone and characterization of natural teeth varies widely, as does translucency, it is rare to encounter natural teeth that resemble a shade guide. Therefore, color and subtle detail adjustments using stains may be necessary. The following presents the author’s recommendations for staining.

Stain and Glaze Application Kuraray/Noritake CZR LF External Stain (LF-ES), from the CZR Press lineup, and LF Internal Stain (LF-IS) are most often used by the author. A mixture of CZR Press Glaze can be applied for a wide range of applications (Fig 8). This creates a more even color appearance with the use of lighter stains rather than the necessity of using darker stains. The diluting liquid used for staining must be an internal stain liquid (IS Liquid), which can also be utilized for applying external stain. CZR Press Glaze matches the coefficient of thermal expansion of zirconia, and leucite crys-

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Translucency

Translucency High translucency through all the disk layers.

High translucency through all the disk layers.

Color

Color

Body (Dentin) Layer

Color of Shade Guide*

Reduced chroma from incisal to the middle layer (① part).

Fig 7 Color and translucency of Katana multilayered zirconia disks.

CZR Press Glaze

CZR External Stain

Fracture strength: 1.57 MPa∙√m

Fracture strength: 1.44 MPa∙√m

9a

8

9b

Fig 8 Kuraray/Noritake CZR internal and external stains, glaze, and internal stain diluting liquid. Figs 9a and 9b Fracture toughness test results of CZR Press Glaze and CZR External Stain. Fig 10 Results of CZR Press Glaze (left) and CZR External Stain (right) sample tabs after baking.

10

tal is found in the composition. In addition to high toughness, the glaze has superior permeability resistance. Figures 9a and 9b show the fracture toughness test results of CZR Press Glaze and CZR External Stain, which produced an average of 2.0 MPa • √m. This performance is higher than that of a general buildup layering porcelain. Figure 10

shows the difference in performance between CZR External Stain (baking temperature 880°C/1,161°F) and a sample tab of CZR Press Glaze at the same temperature. If there are no concerns of matching the shade with the original UTML and STML colors, and only minimum characterization is desired, bake once after applying stain, then

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1

2

3

4

5

1

2

3

4

5

11b

11a

12

Fig 11a Sample tabs of CZR Press Glaze mixed with A+ Stain at the same ratio (5:1) and baked at wide temperature range. (1) Press Glaze only, (2) Press LF External Stain A+ and Press Glaze; (3) Press LF Internal Stain A+ and Press Glaze, (4) CZR External Stain A+ and Press Glaze, (5) Press LF Internal Stain Fluoro and Press Glaze. Fig 11b Same sample tabs with light transmission. Fig 12 One part of blended mixture of incisal stains and gray is mixed with 5 parts of CZR Press Glaze to emphasize incisal translucency.

apply CZR Press Glaze and bake a second time. A mixture of CZR Press Glaze (recommended baking temperature: 850°C/1,562°F) and LF Stain can be baked lower than 850°C/1,562°F, which minimizes the influence on zirconia. Figure 11a shows sample tabs of a mixture of CZR Press Glaze and A+ Stain that were baked at a wide temperature range. All were mixed at a 5:1 ratio of CZR Press Glaze to A+ Stain. Figure 11b shows the appearance with light transmission. Among the sample tabs, the one mixed with internal stain (tab 3) is best in terms of color. The Katana UTML series has a higher translucency. Therefore, if the chroma development is weak, the desired restoration shade may not be achieved. Sample tab 5 in Figs 11a and 11b is a 1:1 mixture of CZR Press Glaze and LF-IS Fluoro. When mixed, the trans-

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13a

13b

Figs 13a and 13b Crown fabricated with UTML EA1 shown with the A2 shade tab of the VITA Classical Shade Guide. (a) Before shade staining. (b) After shade staining, as shown in Fig 12, to emphasize translucency in the incisal one-third.

lucency will decrease slightly. However, for an anterior crown, applying this mixture in approximately the cervical one-half will closely mimic natural tooth fluorescence. For emphasizing translucency, apply a 2:1:2 mixture of LF-IS Incisal Blue 1, Incisal Blue 2, and Gray as a single component. Then mix 1 part of this blended stain component with 5 parts of CZR Press Glaze. Apply this to approximately the incisal one-third (Fig 12). Staining is not easily standardized compared to building up porcelain, as each technician has a different sense of desired viscosity and the application layer is very thin. However, the stain application process requires an ongoing degree of visual evaluation, so the technician will likely soon develop his or her own standard method.

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www.pdflobby.com Clinical Applications of Ultra-Translucent Zirconia Crowns

14

15

16

Fig 14 Silicone rubber point with fine diamond particles is used for surface contour to mimic wax model. Fig 15 Definition of deeper vertical and horizontal grooves on labial side with a Meister Point. Fig 16 Completed crown with surface texture and anatomy adjustments.

Figures 13a and 13b present crowns using the UTML series with staining (tab 3 shown in Fig 11a), and the shading stain as shown in Fig 12. By the time this article is published, Kuraray Noritake will have introduced Cerabien ZR FC Paste Stain, which features a suitable viscosity of powder and liquid pre-blended in 27 shades. The appropriate amount of fluorescence is added to the stains and glaze to enhance the clinical application and appearance of zirconia, which does not have fluorescence. The translucency and strength of Cerabien ZR FC Paste Stain are similar to those of the CZR Press Glaze described earlier, and it exhibits excellent physical properties.

Stain/Glaze Materials and Surface Properties When the CZR Press Glaze and shading stain is applied, the surface anatomy may become flat and incongruous. Therefore, important points of form and contour adjustment are recommended. First, double scan the wax-up for transfer to the CAD/ CAM design so that the accurate shape of the crown and surface anatomy is similar to the wax-up shape. After sintering the milled crowns, adjust the surface anatomy to conform with that of adjacent teeth and to have proper contacts with the opposing tooth.

If staining is not needed, hand polish to finish to a high shine. The potential for propagation of cracks through the material is higher than with conventional zirconia. When smoothening the grooves and striations created by the milling bur of the CAM machine, it is recommended that sharp pointed tools not be used, as they can create even deeper scratches and fissures on the surface. Use a silicone rubber point impregnated with fine diamond particles to contour the surface to mimic the original wax model (Fig 14). To define the deeper vertical grooves of the labial side, use the edge of a disk-shaped Meister Point (Kuraray Noritake Dental), then change to a small-diameter Meister Point to level out the horizontal contours in a lateral direction (Fig 15). Next, sandblast at 2 bar (30 psi) with 50 µm alumina oxide to the crown surface, clean the restoration using a steam cleaner, and then stain and glaze, as described earlier, as necessary. Figure 16 is the completed crown with surface texture and anatomy adjustments. The reason the surface anatomy and contour appearance can become flat is that deeper vertical grooves on the labial sides are filled with glaze material. There are two different methods to prevent or minimize this. In the first method, a thinly diluted mixture of CZR Press Glaze and IS Liquid is applied on the concave areas, and a thicker blended mixture of CZR Press Glaze on the convex areas. In the second method, a thick blended mixture of CZR Press Glaze is applied over the entire surface and then selectively wiped off in the concave ar-

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17b

17a

Figs 17a and 17b Thick blended mixture of CZR Press Glaze is applied over the entire surface and then wiped off in the concave areas to reduce glaze thickness.

Table 1

Strength Testing of CZR Press Glaze Sandblast processing

Shear strength Standard deviation

High-shine polish

19.9

21.0

0.6

7.9

Measurement condition: ISO 9693. Sandblast processing: 2 BAR, 50 µm. High-shine polish: Silicone rubber point impregnated with fine diamond particles.

eas to reduce glaze thickness (Fig 17a). In either case, a slight vibration should be given to flatten the surface of the thick blended glaze material (Fig 17b). In this process, be sure to prevent too much glaze from collecting in the concave areas.

and additional empirical clinical testing and studies are necessary.

CASE PRESENTATIONS Strength Testing of CZR Glaze Table 1 shows the results of shear testing of CZR Press Glaze baked with a release vacuum at 850°C/1,562°F and a 1-minute holding time in air on high-shine, handpolished surfaces compared to sandblasted surfaces. As one can see, there was not much difference between the two in the median value of the shear strength testing. However, the high-shine, hand-polished samples had more variability (higher standard deviation) in sintering strength, whereas the sandblasted samples showed a generally consistent value. Therefore, the author performs the sandblast process for easy quality control and staining workflow. Also, the aciduric strength of CZR Press Glaze did not show any degradation in the evaluation of 4% acetic acid water solution for 16 hours (80°C/176°F) at a solubility of 9.93 µg/cm2. However, these are early test results,

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The following clinical cases present the uses of the Katana Zirconia UTML and STML series. Among the cases there may be some ambiguity as to the reasons behind material selection that may raise some questions, but this may help push the innovation of new materials.

Case 1: Central Incisors This male patient required restoration of his two central incisors. Occlusal force was found to be strong. The target shade was the color of the lateral incisors or a slightly lighter shade. Upon observation, brightness was found to be high near the cervical margins of the lateral incisors and the translucency strong near the incisal edges (low value). In the porcelain buildup method, measures can easily be taken to increase the lightness (high value condition) to

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CASE 1

18

19

20

Fig 18 Color/shade evaluation. None of the natural teeth match the shade guide. A decision must be made whether to adjust saturation based on the A shade, select D2 to emphasize the translucency of the preparation end region, or choose C1 to raise the brightness (increase value) around the cervical part. Fig 19 A 3:1 mixture of D+ and White stains blended with CZR Press Glaze at a ratio of 1:5 (stain mixture to glaze) is applied near the cervical margin of the crown processed from UTML C1 to increase the brightness. A mixture of A+ and CV-2 is applied adjacent to the cervical margin. Fig 20 Translucency of the truncated or prepared incisal area is partially emphasized. The stain used is the same as that shown in Fig 12.

21

22

23

Fig 21 Enamel crack line and slit of the maxillary left central incisor are drawn. Fig 22 When the staining steps have been completed and baked at 840°C/1,544°F, the crown is covered with CZR Press Glaze and LF-IS Fluoro (nearer to the cervical area). Excess glaze material should be wiped from the recess areas, such as the lip groove, gently in a longitudinal direction. Fig 23 Completed multilayered Katana Zirconia UTML shaded crowns. Fig 24 Postoperative intraoral view. Case provided by Dr Akira Nakazawa.

about one-half of the crown (increasing the layers of porcelain such as Opacious Body, or blended dentin powder sandwiching to increase the reflective layer, etc). Careful

24

consideration is necessary for the correct color tone and shade selection of the UTML series when only stains and glazes will be utilized.

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CASE 2

26

27

25

29

28

30

Fig 25 Color/shade evaluation done chairside. The target tooth color is not too different from the gradation of the dentin color to the enamel color seen in the shade guide. Fig 26 Shading stains, as shown in Figs 11a and 12, were applied and baked. Then only LF-ES (external stain) for characterization was applied and baked to set. Fig 27 The stain mixture is applied near the incisal edge, and then most of the area is coated with the fluorescent CZR Press Glaze mixture as shown in Fig 11a (tab 5). Fig 28 At the start of firing, the crown should be held horizontally at the port of the furnace. It should be dried before placing it in vertically. This prevents the thick glaze material from leaking during drying. Fig 29 Intraoral view after cementation. The adjacent natural tooth has a strong translucency at the incisal edge that was not reproduced in the restoration because porcelain layering was not done. Fig 30 Extraoral frontal view showing excellent match and acceptance at conversation distance. Case provided by Dr Kiyonobu Saburi.

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CASE 3

31

32

33

34

Fig 31 Shade taking for first molar inlay. Fig 32 UTML A3.5 was used. The inlay body was milled out from the lower area of the gradation part of the disk, that is, from the area with a less enamel appearance. The inlay was then stain finished. Kuraray/Noritake Panavia V5 Universal (A2) color was used to cement the inlay. Fig 33 On the mesial side of the inlay, the zirconia material can be seen, but there is no particular negative appearance of white restorative material in contrast to the prepared natural tooth. The second premolar adjacent to the inlay is a full zirconia crown using STML A3.5. Surface staining was used to reproduce the enamel crack at the distobuccal developmental groove. Fig 34 As can be seen in this occlusal view, the translucency was not an ideal match, and color tone fusion with the tooth was lacking. However, zirconia was selected for the inlay in this case because abrasion and possible subsequent breakage of the prosthetic material was a concern. Case provided by Dr Atsushi Nakazawa.

Case 2: Single Central Incisor

Case 3: Inlay

This female patient’s right central incisor had some abrasion on the incisal edge and additional characterization, such as a white band, white turbidity, and orange at the incisal edge. The color was not far from the shade guide, except for a part of the incisal mesial center. UTML A2 was chosen.

According to the Katana Zirconia instructions for use, inlay production is possible. In this case, abrasion was already significant; therefore, zirconia was the material of choice for fabrication of the restoration, given its greater physical strength properties as compared to other options.

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CASE 4

35

36

37

38

39

Fig 35 Preoperative view. The patient’s chief desire was an esthetic improvement of the diastema and color of the dentition. The female patient hoped for restorations brighter than her own natural tooth color. Fig 36 Lingual reduction. It is advisable to mark the abutment tooth line angles with a pencil during the procedure. An inclination angle (bevel) of 120 degrees with respect to the tooth axis is provided. Fig 37 Angled view of the abutment model with the preparations for the laminate veneers. Fig 38 Laminate veneer restorations on the abutment model. The finished veneers are 0.5 mm at their thickest points. Fig 39 Full zirconia laminate veneers were fabricated by selecting the UTML EA1 disk. Staining was intentionally minimal. To emphasize the translucency in the prepared incisal area, the stain shown in Fig 12 was selectively applied to the labial developmental grooves. Case provided by Dr Masayuki Yamakawa.

Case 4: Laminate Veneers Laminate veneer restoration of multiple teeth can also be accomplished with full-contour zirconia. Due to this female

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patient’s diastema, the adjacent tooth surface would have contact with veneer restoration. However, this would not impose any stress and so there would be no risk of cracking in the oral environment. For ideal preparation of the

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CASE 5

40

42

41

43

44

Fig 40 Color evaluation and shade taking. The basic color tone is assumed to be NP1.5 (specific to the Noritake Shade Guide). Fig 41 Designed by wax-up, the shape of the dentin structure is digitized for the CAD process with the double scan method. Fig 42 UTML A2 was processed into the shape of a dentin structure. When layering on top, the portion of the zirconia disk with a lot of the gradation dentin layer was used. Fig 43 The 20% white color of LF-IS (Internal Stain) was mixed as shown in Fig 11a, then the basic color tone of the dentin structure was adjusted and applied to the cervical two-thirds. Fig 44 Shade comparison check with shade guide. The stain mixture as shown in Fig 12 was lightly applied to the V-shaped groove near the incisal end of the dentin structure.

abutment teeth when laminate veneers are produced by CAD/CAM, the edges are cut and reduced by about 1.2 mm and the lingual side should have an inclination angle (bevel) of 120 degrees with respect to the tooth axis. When these guidelines are followed and the teeth gently prepared, potential issues during CAM processing are reduced.

Case 5: UTML Series with Porcelain Layered Buildup

thickness is maintained, it is possible to layer porcelain to the crown. The target tooth in this case has a deep translucent layer, especially in the incisal one-third, which is not seen in the shade guide. Determining that the translucency expression would be inadequate with only a thin stain of the surface layer, it was decided to try building the characterization with the CZR Press LF porcelain. For comparison, two versions were made: one milled from UTML A2 that was stained and glazed, and the other a dentin structure that had the porcelain layered on it. Both were then tried in the oral cavity.

For the UTML series and STML series, the minimum thickness for maintaining strength is specified as 0.8 mm. If this

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45

46

47

Fig 45 Buildup of the LF porcelain LT0 from the CZR Press system. Because of the thickness of the UTML in the cervical margin area, there is no space for porcelain buildup. Fig 46 After LF porcelain buildup in the incisal area, the stain mixture was applied and baked as shown in Fig 11a (tab 5) to the solid UTML zirconia exposed near the margin. Fig 47 Comparison of the two completed ceramic crowns with shade guides: (left) stain and glaze method; (right) porcelain layering method. Fig 48 UTML full zirconia crown finished with only staining/glazing. Panavia V5 Universal (A2) color try-in paste was used on the inner surface of the crown. In the incisal area, the result was lacking in detail and translucency, but the basic color tone was achieved. Fig 49 UTML A2 crown with porcelain layering. Again, the layering method has more flexibility in reproducing the translucent layer. The only concern was whether the white surface stain was made too excessive. Fig 50 Clinical follow-up 2 weeks after completion. Case provided by Dr Yumiko Amakawa.

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48

49

50

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CONCLUSION

ACKNOWLEDGMENTS

In the past, the performance of traditional CAD/CAM technologies required the technician’s eyes and a lot of labor by hand. However, materials introduced in this article demonstrate that we have taken the first steps in the process of easier “color reproduction.” With CAD/CAM and its many available materials, which are improving rapidly, we are in a position to select materials according to specific requirements of our patients. However, as can be seen from the clinical cases presented, this still requires human eyes and hands. Dental technicians need to understand the characteristics of the materials and explore how to use each technology to their advantage, operate within the technical environment, and develop strong chairside relationships.

The author would like to express gratitude and appreciation to Dr Yumiko Amakawa, Amakawa Dental Office Gaienmae; Dr Masayuki Yamakawa, Sakae Swan Dentistry; Dr Kiyonobu Saburi, Saburi Dentistry; Dr Atsushi Nakazawa, Nakazawa Dental Clinic; Dr Toshizumi Hino, Hino Dental Clinic; as well as to everyone at Quintessence Publishing for this publishing opportunity and to Kuraray Noritake Dental for producing the materials.

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REFERENCES 1. Shinsho F. New strategy for better geriatric oral health in Japan: 80/20 movement and Healthy Japan 21. Int Dent J 2001;51:200– 206. 2. Ishii T. The meaning and problem of the 8020 movement in Japan [in Japanese]. Nihon Hotetsu Shika Gakkai Zasshi 2005;49:168–178. 3. Kwon S, Lawson NC, Beck P, Bansal R, Burgess J. Bond strength, wear, and enamel wear of translucent zirconia. Presented at the American Association for Dental Research Meeting, Los Angeles, March 17, 2016.

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Multidisciplinary Approach Using Slow Orthodontic Extrusion and the Immediate Dentoalveolar Restoration Technique José Carlos Martins da Rosa, DDS, MSc, PhD1 Juliana Romanelli, DDS, MSc2 Luis Eduardo Calicchio, DDS3

R

econstruction of the bone and soft tissue architecture around teeth with implant-supported restorations continues to be a major challenge. Better understanding of the biology of peri-implant tissues and the limitations of implant treatment can aid in obtaining more predictable restoration outcomes in the esthetic zone, particularly for single-tooth restorations. However, in complex cases, such as for patients with extensive bone and gingival defects and with teeth that are in a state of collapse, selecting the ideal restoration strategy can be difficult. For such complex cases, three reconstruction strategies can be used: (1) surgical tissue reconstruction, (2) dentogingival prosthesis, or (3) regeneration of the soft

Specialist in Periodontics and Prosthodontics, São Paulo Association of Dental Surgeons, São Paulo, Brazil. 2 Specialist in Orthodontics, São Paulo, Brazil. 3 Private Practice, Associate Director of Ateliê Oral, São Paulo, Brazil. 1

Correspondence to: José Carlos Martins da Rosa, Av. São Leopoldo 680, CEP 95097-350, Caxias do Sul, RS – Brazil. Email: [email protected]

and hard tissues by the immediate dentoalveolar restoration (IDR) technique combined with slow orthodontic extrusion (SOE). Surgical reconstruction of hard and soft tissues through bone grafting and tissue augmentation can be done before or at the same time the implant is placed. Although good results can be obtained in some cases with bone defects, predictable results are difficult to achieve and, in many instances, require multiple substantial compensatory surgical interventions. As a result, it is difficult to predict how well the tissues will develop back into their original positions. In the dentogingival prosthesis, the gingival portion is made in acrylic resin, composite resin, or porcelain that is colored pink to mimic the gingival tissue. Good esthetic results can be obtained, especially when multiple prostheses are required. However, long-term hygiene or phonetics maintenance is not always ideal, particularly for patients who are susceptible to periodontal problems. Moreover, patients may be apprehensive of this therapy because the lost hard and soft tissues are substituted with an artificial device.

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www.pdflobby.com ROSA ET AL The multidisciplinary treatment approach using SOE to move the soft and hard tissues coronally combined with the IDR technique has shown particular benefit in cases of asymmetry of the bone and soft tissues in the esthetic zone in unnrestorable teeth. Use of the IDR technique for alveolar reconstruction has led to important improvements in terms of the long-term stability of the soft tissues because the biological properties of the technique favor faster and more effective bone incorporation. This technique has proven efficient in preventing bone resorption and gradual loss of graft volume. Moreover, the technique promotes maintenance of the tissue architecture of the gingiva and papilla.1–3 This article presents a clinical case of multidisciplinary treatment involving orthodontics and implant rehabilitation with immediate reconstruction of alveolar bone defects of both maxillary central incisors. The clinical results support the idea that this approach is a viable option for implantsupported rehabilitation.

MULTIDISCIPLINARY TREATMENT FOR COMPLEX CASE Multidisciplinary treatment needs to be well-coordinated and systematically directed, with excellent communication among all involved specialists. In this complex clinical case, SOE4 was used initially to improve positioning of the gingival and papilla line in the apicocoronal direction before performing IDR and finalizing the restoration, as described below. A 32-year-old woman visited the authors’ office seeking a solution to trauma-induced loss of bone and gingival tissues in the esthetic area. Initial analysis showed that both maxillary central incisors could not be saved (Figs 1a to 1d). The fact that they were consecutive teeth to be restored by implants made the esthetic prognosis dubious with respect to formation of the interdental papilla.5 Extensive bone loss in the “U” between the teeth was an aggravating factor that made it difficult to plan surgery with any predictability. Loss extended from the mesial side of the root of the right lateral incisor to the same area on the left lateral incisor, with a lack of papillae between the central and lateral incisors on both sides.

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Step 1: Basic Preparation Basic prophylactic periodontal therapy (three sessions), treatment of caries, and endodontic treatment were performed to prepare the patient and to stabilize the affected teeth. Periodontal and endodontic treatment should always be performed before orthodontic extrusion.

Step 2: Slow Orthodontic Extrusion Vertical bone and soft tissue volumes can be augmented by coronally repositioning the clinical levels of periodontal insertion through SOE of the involved teeth. Treatment time depends on the amount of apicocoronal movement required. A minimum of 3 months of fixed containment is needed to allow for complete mineralization of the bone and maturation of the anatomical contours of the soft tissues around the compromised teeth.6 For the SOE concept to be utilized, adjacent pillars need to be present. The teeth to be extruded may have damaged tissues, but there must be sufficient periodontal insertion to allow for gradual movement in the coronal direction. SOE achieves superior results over other surgical techniques for tissue reconstruction in terms of periodontal tissue and papillae changes and low morbidity.7,8 The technique enables bone and gingival gains of the appropriate height and thickness in the vertical and horizontal directions. These advantages facilitate implant placement in the ideal three-dimensional (3D) position and correct implantcrown proportion, and they simplify the design and manufacture of the prosthetic crown, thereby allowing for a more predictable outcome. Patients are receptive to this treatment because they know that they will get clinical crowns that are compatible with their natural teeth. This case involved orthodontic treatment by SOE to facilitate dental extrusion. The traumatically lost alveolar bone was recreated by traction of the unrestorable maxillary central incisors until the inserted bone overcorrected for the loss. To achieve this objective, SOE was performed at a velocity of approximately 1 mm per month. The amount of movement that is needed determines the extrusion time. As this patient required a large amount of traction, a 2-month “rest” period was included in the treatment to allow for maturation of the formed tissue. An orthodontic device (Equilibrium Mini, Dentaurum) was inserted to achieve an initial basic leveling (Fig 2). SOE was

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Figs 1a to 1d Initial photographs and periapical radiograph showing the loss of bone and gingival architecture with significant loss of papilla between the central incisors. The two maxillary central incisors were planned to be extracted.

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Fig 2 Passive bonding of brackets for initial leveling of teeth.

begun, with the maxillary left central incisor being chosen as the first to be tractioned. The choice of this tooth was random because both teeth required extraction in this case. In cases where only one of the teeth is condemned and needs to be extracted, that tooth should be extruded first, in a continuous way, until it is substituted by the implant. Then, after bone remodeling and accommodation of this procedure by the peri-implant tissue, the adjacent tooth can be tractioned up to the limit of being just maintained in

the mouth. In cases where both teeth are to be extracted but one tooth is in a better position of insertion visually and in better periodontal health, the tooth in the poorer situation should be extruded first. This consideration is supported by the fact that the tooth with a greater volume of periodontal insertion and, consequently, irrigation, allows better formation of new bone that is enabled through extrusion of the less-favorable tooth.

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Figs 3a to 3c First phase of the SOE technique, with extrusion of the left central incisor. Figs 4a and 4b (a) After extrusion of the right central, (b) the teeth were adjusted to provide a more triangular shape that favors papilla formation. Fig 5 Remarkable formation of the interproximal gingival tissue in the buccal and palatal aspects, with a greater volume in the palatal due to the greater irrigation in this region. Figs 6a to 6c (a) End of slow orthodontic extrusion. (b) Provisional restorations placed on the extruded teeth. (c) Bonding of the brackets for the wire to passively enter the stabilization phase with no tooth movement.

The sequence for the first phase of the technique (Figs 3a to 3c) took 45 days—from the first apical position of the bracket on the left central incisor to the final stipulated movement. The total extruded length was 1.5 mm. Thus, the extrusion velocity, which was fundamental to treatment success, was 1 mm per month. Among the various methods available for performing SOE, the technique involving wires with slight memory was used in this case. Wires were arranged for successive apical repositioning of the bracket.9 Because of the square shape of the teeth, good formation of the interdental papilla was impossible. The best way to proceed with the planned reconstruction of the papilla was by adjustment between the teeth from an appropriate

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height to the point of contact between them (Figs 4a and 4b). In this way, the tissue and space that were created through extrusion could be accommodated. The result could be verified within 30 days, during extrusion of the left central incisor. In most cases, the result can be seen first on the palatal and later on the vestibular side. The palatal region has good irrigation, which promotes rapid and extensive growth in this area (Fig 5). To ensure that there was no interference with the bite during the extrusion maneuver, the incisal and palatal sides of the tooth were preventatively adjusted. During extrusion, it was observed that a portion of the root in the cervical area remained exposed, indicating that there was a sub-

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www.pdflobby.com Multidisciplinary Approach Using SOE and the IDR Technique Fig 7a After orthodontic extrusion, the crestal bone between the central incisors was missing. Fig 7b CBCTs showing the absence of the buccal bone walls in both central incisors. Figs 7c to 7e The buccal probing depth was approximately 10 mm and 9 mm in the right and left central incisors, respectively. 7a

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gingival region without periodontal insertion. In some cases, root exposure can indicate rapid orthodontic extrusion, in which heavy force is used and the periodontal ligament is injured. To finalize the SOE process, the brackets were repositioned passively (Figs 6a to 6c) using stiff rectangular wires, so that there was no more movement. At the end of the extrusion process, the teeth had a reasonable amount of mobility. During a 6-month stabilization phase, the patient’s elastic bands were changed but there was no tooth movement. The aim of this “rest period” was to allow the newly formed bone to mature. Bone maturation is fundamental to the success of implant treatment. At the end of the stabilization period, 6 months later, the gingival volume was maintained and the teeth were no longer mobile. The patient was evaluated by tomography before implant placement. Evaluation revealed the apex of the roots of the extruded teeth beneath the gingival tissue in the vestibular region. The case proceeded to the surgical phase. To make the surgical guide and provisional prostheses and to carry out the surgery without interference, the orthodontic brackets were removed from the anterior region, to be replaced after surgery. After osseointegration of the implants and complete maturation of the peri-implant tissues, the absence of periodontal insertion of the mesial cervical thirds of the lateral incisors made the papillae migrate in the apical direction. Therefore, with the orthodontic brackets in

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the mouth, the lateral incisors were extruded, by approximately 1.5 mm each, to move the interproximal bone crest in the coronal direction. This step supported appropriate formation of papillae in the distal area of the implants.

Step 3: Immediate Dentoalveolar Restoration This step involves a surgical and prosthetic protocol for bone and soft tissue reconstruction to keep the gingival architecture stable. The IDR technique allows for implant placement in the compromised socket after extraction, reconstruction of the socket using the maxillary tuberosity as the donor area, and immediate provisionalization in a single procedure.1,2,10,11 The IDR approach has many benefits: it is a minimally invasive technique, avoids the need for complex grafting surgeries of the bone and/or gingival tissue, and reduces morbidity by harvesting a graft from the maxillary tuberosity.1,2 After the slow orthodontic forced eruption was completed and the positioning of the coronal gingival architecture improved, the IDR technique was applied. Both central incisors still presented total loss of the buccal walls and crestal bone deformity after orthodontic treatment; however, a good amount of available bone was present beyond the root apex (Figs 7a to 7e). The surgical guide and pro-

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Figs 8a to 8c Correct emergence profile built over stone cast in both central incisors. Figs 8d to 8f Construction of the (d and e) provisional prosthesis and (f) surgical guide.

visional prosthesis were manufactured on a stone cast, which defined the ideal anatomical contour of the gingival margin of the central incisors (Figs 8a to 8f). Considering the esthetic and functional demands, a treatment plan was developed including the following steps: atraumatic extraction of the teeth (Figs 9a and 9b); curettage of the sockets; immediate placement of implants in the correct 3D position, while achieving primary stability and leaving a gap of approximately 3 mm in the labial aspect (Figs 10a to 10g); construction of a provisional pros-

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thesis with the ideal emergence profile; reconstruction of the alveolar bone defects by using the IDR technique, as described elsewhere1–3,10,11; and use of corticocancellous bone grafts harvested from the maxillary tuberosity (Figs 11a to 11c) to restore the lost socket walls and crestal bone between the central incisors. Buccal bone defects were restored with corticocancellous bone harvested from the maxillary tuberosity. The graft was shaped to the defect, while maintaining a biological distance of 2 to 3 mm to the gingival margin. Residual gaps were filled with can-

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www.pdflobby.com Multidisciplinary Approach Using SOE and the IDR Technique

Fig 9a The hopeless right central incisor was extracted using a minimally invasive procedure that favored preservation of the remaining bone walls.

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Fig 9b Clinical evaluation with a periodontal probe confirmed the extension of buccal bone defect.

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Figs 10a and 10b Site preparation of the palatal wall of the right central incisor. Fig 10c The implant was anchored in the remaining apical bone and at the palatal wall. Figs 10d and 10e Surgical guide in position. Figs 10f and 10g Evaluation of the gap and dimension of bone to be restored on the labial aspect of both central incisor sites.

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Fig 11a CBCT images show the amount of bone height and width available in the right tuberosity. Figs 11b and 11c Corticocancellous graft harvested from the maxillary tuberosity.

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Figs 12a and 12b Reshaping of the graft according to defect configuration using a rongeur. Fig 12c Corticocancellous graft was inserted to restore the buccal wall, and particulate bone was compacted to completely fill the gaps between the marrow portion of the graft and the implant in both central incisor sites. Particulate bone graft was also carefully inserted and compacted underneath gingival papilla between the central incisors to restore crestal bone.

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Fig 13a Provisional prosthesis was inserted with an adequate emergence profile to allow space for the correct accommodation of the tissues. Fig 13b Periapical radiograph shows the bone compacted in the crestal area.

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Fig 14 Periapical radiograph 6 months postoperatively shows the crestal bone completely remodeled.

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www.pdflobby.com Multidisciplinary Approach Using SOE and the IDR Technique Fig 15 Mock-up in position. The soft tissue had healed and maintained an appropriate position. Fig 16a Peri-implant soft tissue healed. Fig 16b Occlusal view of final teeth preparation shows that the anatomical contour of the soft tissue was maintained.

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cellous bone harvested from the same donor area, while maintaining the reconstructed bone walls and surrounding soft tissue. Crestal bone damage between the central incisors was carefully curetted and filled with particulate cancellous bone while preserving the papilla integrity (Figs 12a to 12c). The provisional prosthesis was positioned immediately and out of occlusion. A periapical radiograph verified the reconstructed bone in the crestal area (Figs 13a and 13b). After 6 months, radiography verified that the crestal bone was completely restored between the implants (Fig 14). The definitive restoration could now be accomplished.

Step 4: Final Restoration Prosthetic rehabilitation involved the construction of customized zirconia abutments and individual metal-free leucite-reinforced crowns, leading to satisfactory esthetic results. After completing the IDR phase, new anatomical documentation was obtained, including new photographs of the patient’s face and intraoral areas and new videos for esthetic reevaluation. Ceramic veneers were needed on

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the lateral incisors and canines, with crowns over the implants on the central incisors, to obtain suitable shape and size distributions. Readjustment of the smile was confirmed with a bis-acryl resin mock-up (Fig 15). After the dentist and patient approved the new smile contour, tooth preparations were initiated. Rubber wheels for ceramic were used to polish the preparations (Figs 16a and 16b). Impressions of the implants and prepared teeth were made using the double-impression technique. On the prepared natural teeth, cords 000 and 0 (Ultrapak, Ultradent) were used. An important element is customizing the impression transfer caps; in this case, the authors opted for a closed-tray impression technique. To customize the transfer caps, provisional crowns were fitted for the central incisors, which already had their correct emergence profiles for future restorations defined in the analogs. With the addition of silicone, an impression was taken of the unit up to the cervical area of the provisional crowns. After the impression material hardened, the crowns were removed and the analogs left inside the mold. The caps were screwed onto the analogs and, using acrylic resin (Pattern Resin, GC), transfer of the whole emergence profile was completed. Customized transfers were fitted in the mouth, and

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periapical radiographs were used to check their correct adaptation with the implant. The two-step impression was then performed, first with the addition of heavy-body followed by light-body silicone (Honigum and Silagum, DMG). In the laboratory, veneer restorations for the lateral incisors and canines were digitally manufactured using Empress CAD ceramic (D’sign, Ivoclar Vivadent) (Fig 17). Abutments for the central incisor implants were made with zirconia, which was chosen for its biological and biomechanical properties. Lithium disilicate ceramic (e.max, Ivoclar Vivadent) was applied over the zirconia abutments on the cervical and middle thirds to gain fluorescence and adhesion. The e.max is an acid-sensitive material, favoring the cementation of future full crowns made with Empress CAD ceramic (D’sign). The cervical anatomical contour of the abutments followed a concave design in the transmu-

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cosal region, as described by Rompen et al,12 to minimize gingival recession (Figs 18a to 18c). Color, shape, and contact points of the restorations were checked and approved (Figs 19a to 19c). Ceramics were conditioned outside the mouth using 10% hydrofluoric acid for 90 seconds. According to Peumans et al,13 acid conditioning creates microretentions on the restoration surface, increasing adhesion with resin cement. The restorations were cleaned with 35% phosphoric acid (scrubbing the surface for 10 seconds), followed by abundant washing and drying. They were placed in an ultrasonic bath with distilled water for 5 minutes to remove residual acid and then were dried. Silane was applied for 1 minute, and the restorations were dried at 100°C for 1 minute.

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www.pdflobby.com Multidisciplinary Approach Using SOE and the IDR Technique

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Fig 17 Empress CAD veneers on model.

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Fig 18a Zirconia abutments on model.

Fig 19a Checking adaptation of zirconia abutments. The cervical anatomical contour of the abutments accommodated the soft tissue volume on the labial and proximal aspects.

Fig 18b Customized zirconia abutments.

Figs 19b and 19c Checking contact points of the crowns.

Fig 18c Final customized zirconia abutments and final crowns.

Figs 20a and 20b Cementation of crowns with resin cement.

Cementation of the restorations was performed using rubber dam isolation (Figs 20a and 20b). The dental surfaces were cleaned with pumice stone and water, rinsed abundantly with water, and surface dried. The teeth preparations were conditioned with 35% phosphoric acid for 15 seconds. The surface was again washed with abundant water and dried. Three to four layers of adhesive (SingleBond, 3M) were applied, according to the manufacturer’s recommendation. Without polymerizing the adhesive, resin cement (Variolink, Ivoclar Vivadent) was applied to the interior of the veneers and they were placed in the mouth for correct adaptation in the prepared areas. Excess cement was removed with cotton balls, dental floss, and delicate brushes, while carefully stabilizing the restoration in position. Restorations were light cured for 3 seconds. The remaining cement was removed using the blade of a #12D scalpel and strips of serrated metal (Komet). The restorations were light cured for 60 seconds on each side.

Customized lithium disilicate abutments were conditioned outside the mouth with 10% hydrofluoric acid for 20 seconds. The protocol for ceramic conditioning was followed in the same way as described above. Abutments were placed on the implants and torqued to 35 N. Crown cementation followed the same steps and involved the same materials as the veneers. Occlusal adjustment was performed with carbon paper to correctly distribute the occlusal contacts during protrusive and excursive movements. Final impressions were made in silicone to obtain the rigid occlusal protector. The digital ceramic restorations recreated the correct emergence profile and shape of natural teeth (Figs 21a to 21d) and provided ideal soft tissue support (Figs 22a and 22b). The patient was followed up for 3 years. Clinical and radiographic images taken from the 3-year follow-up appointment demonstrate that the conditions and levels of bone and gingival architecture remained stable (Figs 23a to 23c).

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Figs 21a to 21d Final result after cementation of crowns. Dental technician: Wagner Nhoncance.

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Fig 22a Occlusal gingival contour showing stability of the soft tissue. Fig 22b Emergence profile of the final crowns.

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Figs 23a and 23b Clinical photographs at 3-year follow-up show harmony between lips, crowns, and gingival architecture. Fig 23c Radiograph at 3-year follow-up shows stability of the crestal bone between the implants and bone stability between the implants and neighboring teeth.

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BENEFITS OF USING THIS MULTIDISCIPLINARY APPROACH 1. Less invasive surgery: This type of treatment prioritizes preservation instead of complex reconstruction involving soft and hard tissue grafts. Surgical morbidity for patients is reduced by avoiding invasive procedures. Thus, satisfactory esthetic results can be achieved with more predictability. 2. Ease of making the prosthetic crown: The manufacturing technique for the restorations is simplified because the prosthetic restoration essentially restores the clinical crown. By contrast, dentogingival prostheses are complicated to use and are often rejected by patients. 3. Biomechanical aspects: The crown-implant proportion is optimized, and complex prosthetic reconstructions involving cantilevers of the dentogingival prosthesis are avoided. 4. Simplified oral hygiene and maintenance: An appropriately designed prosthesis with single crowns of ideal shapes and contours makes maintenance and oral hygiene procedures easier, with clear long-term benefits in terms of maintaining peri-implant tissue health. 5. Phonetics: In patients with advanced bone and papillary loss, reconstituting an ideal relationship between the teeth and soft tissues avoids the phonetic complications that can be caused by large spaces in implantsupported fixed prostheses. 6. Biological restoration: In contrast with more complicated graft procedures, the approach of using SOE with IDR achieves an ideal biological restoration of the soft and hard tissues. 7. Tissue stability: This approach reduces risks of resorption and gradual loss of the graft volume, complications that are seen with most surgical techniques used for grafts involving large reconstructions in esthetic areas.

CONCLUSION An excellent functional, biological, and esthetic result was maintained after 3 years of follow-up, with vertical and horizontal bone stability. In addition, the soft tissue architecture was maintained in terms of the esthetic stability of the contours of the gingival and papillary margins. For patients affected by trauma and major tissue loss, as in the case described, a multidisciplinary approach involving

SOE of the compromised teeth and IDR can offer an excellent method for esthetic rehabilitation, particularly in the vertical augmentation and regeneration of bone and soft tissues. This approach can improve the results of implantsupported restorations. Meticulous surgical and prosthetic treatment, excellent hygiene control, and careful maintenance are essential.

REFERENCES 1. Rosa JC, Rosa AC, Fadanelli MA, Sotto-Maior BS. Immediate implant placement, reconstruction of compromised sockets, and repair of gingival recession with a triple graft from the maxillary tuberosity: A variation of the immediate dentoalveolar restoration technique. J Prosthet Dent 2014;112:717–722. 2. Rosa JC, Rosa AC, Francischone CE, Sotto-Maior BS. Esthetic outcomes and tissue stability of implant placement in compromised sockets following immediate dentoalveolar restoration: Results of a prospective case series at 58 months follow-up. Int J Periodontics Restorative Dent 2014;34:199–208. 3. Rosa JCM (ed). Immediate Dentoalveolar Restoration: Immediately Loaded Implants in Compromised Sockets. Sao Paulo: Quintessence, 2014. 4. Salama H, Salama M. The role of orthodontic extrusive remodeling in the enhancement of soft and hard tissue profiles prior to implant placement: a systematic approach to the management of extraction site defects. Int J Periodontics Restorative Dent 1993;13:312–333. 5. Salama H, Salama MA, Garber D, Adar P. The interproximal height of bone: a guidepost to predictable aesthetic strategies and soft tissue contours in anterior tooth replacement. Pract Periodontics Aesthet Dent 1998;10:1131–1141. 6. Mankoo T. Esthetic rehabilitation of the periodontally compromised dentition: A novel interdisciplinary approach using orthodontic extrusion and dental implants. J Cosmet Dent 2014;29:12. 7. Mirmarashi B, Torbati A, Aalam A, Chee W. Orthodontically assisted vertical augmentation in the esthetic zone. J Prosthodont 2010;19: 235–239. 8. Rose TP, Jivraj S, Chee W. The role of orthodontics in implant dentistry. Br Dent J 2006;201:753–764. 9. Romanelli J. Excelência nas finalizações estéticas e periimplantares. In: Napoleão (ed). Especialidade em foco: Beleza do Sorriso. Brasil: Napoleão, 2013:216–245. 10. Rosa AC, Francischone CE, Cardoso MeA, Alonso AC, Filho LC, Rosa JC. Post-traumatic treatment of maxillary incisors by immediate dentoalveolar restoration with long-term follow-up. Compend Contin Educ Dent 2015;36:130–134. 11. Rosa AC, Rosa JC, Dias Pereira LA, Francischone CE, Sotto-Maior BS. Guidelines for selecting the implant diameter during immediate implant placement of a fresh extraction socket: A case series. Int J Periodontics Restorative Dent 2016;36:401–407. 12. Rompen E, Raepsaet N, Domken O, Touati B, Van Dooren E. Soft tissue stability at the facial aspect of gingival converging abutments in the aesthetic zone: A pilot clinical study. J Prosthet Dent 2007;97(6 suppl):S119–S125. 13. Peumans M, Van Meerbeek B, Lambrechts P, Vanherle G. Porcelain veneers: A review of the literature. J Dent 2000;28:163–177.

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Copyright of Quintessence of Dental Technology (QDT) is the property of Quintessence Publishing Company Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

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Enrique Diaz, DDS1 Julian Conejo, DDS, MSc2 Julio Flores, CDT3 Markus B. Blatz, DMD, PhD4

Private Practice, Mexicali, México. Visiting Professor, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania, USA. 3 Dentaltek Lab, Michoacán, México. 4 Professor of Restorative Dentistry and Chairman, Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania, USA. 1 2

Correspondence to: Dr Julian Conejo, Robert Schattner Center, University of Pennsylvania School of Dental Medicine, 240 South 40th Street, Philadelphia, PA 19104, USA. Email: [email protected]

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Full-Mouth Rehabilitation with the Flowable Injection Technique

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www.pdflobby.com DIAZ ET AL

T

he necessity for full-mouth rehabilitations in young adults with noncarious lesions is a common challenge for clinicians.1 The dilemma as to whether to prepare these teeth for indirect ceramic restorations or restore them without any preparation at all is yet another challenge to the thorough decision-making process that full-mouth rehabilitations require.1 Additive techniques with CAD/CAM indirect restorations are commonly used to minimize the reduction of healthy tooth structures.2 The decrease in tooth hypersensitivity and in many cases evasion of endodontic treatments are some of the benefits this concept provides.3 The flowable injection technique in combination with prosthodontic occlusal and esthetic concepts offers a different approach for restoring teeth suffering from the effects of erosion and bruxism. This article presents the clinical application of this technique in a step-by-step manner so dentists can incorporate it into their treatment armamentarium.4

TREATMENT GUIDELINES To achieve long-term high success rates, prosthodontic guidelines for proper diagnosis and treatment planning should be followed. Simplified techniques to obtain esthetic and functional results by means of detailed clinical execution will provide high-quality dental care for our patients.5 Proper evaluation and reestablishment of the occlusal vertical dimension (OVD) with a correct clinical application is crucial for minimally invasive full-mouth rehabilitations. By increasing the OVD, new interocclusal restorative space is created without the need to remove healthy tooth structure.6 According to the Glossary of Prosthodontic Terms, maximal intercuspal position (MIP) is the best relation between the opposing teeth independent of the condylar position.7 This position is used when a limited number of restorations with no occlusal scheme changes are required. In fullmouth rehabilitations, however, the centric relation (CR) position should be used. CR is defined as “a maxillomandibular relationship, independent of tooth contact, in which the condyles articulate in the anterior-superior position against the posterior slopes of the articular eminences; it is a clinically useful, repeatable reference position.”7 When

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using the CR position as a reference, centric occlusion (CO), defined as the occlusion of opposing teeth when the mandible is in centric relation, is obtained.7 For proper diagnosis and modification of the OVD—the distance measured between two points when the occluding members are in contact7—a semi-adjustable articulator is recommended. A facebow is necessary to record the spatial relationship between the maxillary arch and some anatomic reference points and then to transfer this relationship to the articulator.8 Pretreatment with functional occlusal mock-ups before elaboration of the final restorations is a crucial step for fullmouth rehabilitations that involve changes in the OVD.9 A clear polyvinyl siloxane (PVS) impression material is used to replicate the diagnostic wax-up at the new OVD. This clear PVS matrix is placed over the unprepared tooth to transfer the new morphology with the flowable resin composite into the oral cavity. The flowable composite is injected through the matrix and then cured. This novel technique shows promising short-term results, although longevity remains to be determined.4 One of the other advantages of this technique is that, due to its noninvasive nature, it does not prevent the future use of traditional treatment modalities, such as indirect ceramic partial-coverage restorations, which have proven long-term success rates.10,11

CASE PRESENTATION A female patient, 23 years of age, presented with esthetic concerns related to defective Class 4 composite restorations on the mesial of both the maxillary right and left central incisors. She also experienced hypersensitivity and discomfort on the mandibular right first molar due to a fractured Class 1 (mesiobuccal) composite restoration. Preoperative intraoral and extraoral images following the Digital Smile Design (DSD) documentation protocol were taken (Figs 1 to 3). After maxillary and mandibular impressions with PVS (Figs 4a and 4b), a facebow record was obtained (Artex, Amann Girrbach) (Figs 5a and 5b). To mount the casts in a CR position on a semi-adjustable articulator, leaf gauges and bite registration material (Aluwax Dental Products) were used to avoid contacts between antagonist teeth

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www.pdflobby.com Full-Mouth Rehabilitation with the Flowable Injection Technique

Fig 1 Preoperative facial view. Figs 2a to 2c Preoperative views of patient’s smile. Figs 3a to 3c Preoperative intraoral views of the maxilla and mandible.

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Figs 4a and 4b Maxillary and mandibular PVS impressions. Figs 5a and 5b Facebow record.

during the CR record (Figs 6a and 6b). The maxillary cast was mounted first with the corresponding transfer table (Artex, Amann Girrbach). After rigid stabilization of both casts with metal pins and sticky wax, the mandibular cast was mounted (Fig 7). OVD was increased by 3.0 mm anteriorly by raising the incisal pin, creating a 1.0-mm interocclusal space on the molars. This modification of the OVD provided adequate space to recreate the natural length of the worn anterior teeth following natural tooth proportions for optimal esthetics. A new anatomy of posterior occlusal

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surfaces was planned to recreate ideal posterior support (Fig 8). After duplication of the study models, a second set of models with removable dies (Geller type) was fabricated to optimize the relation between the wax-up and soft tissues to avoid overcontours. This second set of models was also mounted on the articulator through cross-mounting. A fullmouth wax-up was performed in the laboratory with the objective of designing a new smile with a mutually protected occlusion, essential for the long-term success of any fixed dental restoration (Fig 9).

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Figs 6a and 6b Leaf gauges for centric relation bite registration.

Fig 7 Maxillary and mandibular casts mounted on the articulator.

Fig 8 Increase of the OVD with the incisal pin.

Fig 9 Frontal and lateral views of the wax-up.

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Figs 10a and 10b Duplication of maxillary and mandibular wax-ups. Figs 11a and 11b Maxillary and mandibular indexes for mock-up. Fig 12 Bis-acryl material.

The maxillary and mandibular wax-ups were duplicated with a silicone material for laboratory use (Elite Double, Zhermack) (Figs 10a and 10b). PVS silicone indexes with light body and putty mass were also made from the waxups to fabricate the full-mouth mock-up (Figs 11a and 11b). B1-color bis-acryl material (Fig 12) was injected into the indexes and firmly placed over the teeth in the patient’s mouth to create the mock-up. After excess material was removed, the mock-up was polished and finished. Intraoral and extraoral photographs and videos were taken to provide visual images for the patient when discussing treatment options. These steps are crucial for raising patient acceptance when full-mouth rehabilitations are needed (Figs 13 and 14). The patient preferred direct resin composite restorations due to their conservative nature in relation to tooth structure reduction and their lower cost in comparison to ceramic restorations. After evaluation of the mock-up for 1 month, the patient did not report any pain or discomfort

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and no fractures were observed. The patient wears this prototype 24 hours a day for esthetic, phonetic, and functional evaluation, providing a stable and favorable position for the TMJ and masticatory muscles. When no modifications to the wax-ups are needed, as in this case, impressions with transparent material are made to fabricate the matrixes. The transparent PVS material (Exaclear, GC Corporation) was injected into the transparent impression trays. Prefabricated transparent trays (RSVP Tray, Cosmedent Inc) were utilized for the posterior area. For the anterior teeth, however, custom trays were fabricated to provide support for the transparent PVS material (Figs 15a to 15f). The trays were placed inside a pressure pot (Aquapres, Lang Dental Mfg Co) to limit air bubbles in the PVS material (Fig 16). Such air entrapments may compromise visibility of the composite during the injection process and should, therefore, be avoided.

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Figs 13a to 13e Transfer from wax-up to mock-up.

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Figs 14a to 14d Patient’s smile with the mock-up in place.

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Figs 15a to 15f Transparent trays.

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Fig 16 Pressure pot. Fig 17 Perforations of the transparent index should have the same diameter as the tip of the resin composite injection syringe.

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After the excess material in the cervical area was removed, the transparent PVS index was perforated with a coarse diamond bur for crown preparations. The perforations were located on the incisal edges of each anterior tooth and on the buccal cusps of each posterior tooth. These perforations provide access to the tip of the flowable composite syringe (Fig 17). Therefore, the diameter of the bur has to be the same as the diameter of the sy-

ringe. Polytetrafluoroethylene film was placed to protect the mesial and distal teeth prior to etching and bonding procedures. Phosphoric acid was applied for 15 seconds. After thorough water rinsing, the adhesive system was applied on the etched tooth surface, air thinned, and light cured (Fig 18).12 The transparent silicone index was positioned and stabilized while the flowable composite was injected. A flowable nanohybrid composite material (Tetric

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EvoFlow, Ivoclar Vivadent) with the shade Bleach L was injected and light cured for 10 seconds (Figs 19a to 19d). Nanohybrid resin composite materials are preferred due to their improved optical and physical properties.13,14 After the silicone index was removed, a glycerin layer was placed over the composite restoration for additional light curing (40 seconds). Excess material was removed carefully with a scalpel blade (#12) and interproximal finishing strips (Figs 20a to 20e).

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Figs 18a to 18d Total-etch technique was utilized before placement of the restorative material.

Figs 19a to 19d Injection and light curing of the flowable resin composite material through the transparent index.

It is critical to inject each tooth individually to obtain proper proximal contact areas that provide access for cleaning with dental floss. The same technique was used for the posterior teeth (Figs 21a to 21c). Low-speed disks were used to polish the buccal and incisal surfaces of the composite restorations (Fig 22). After the full sequence of the disks, a smooth surface was created with diamond-impregnated silicone points and goat-hair brushes. A cotton buff with composite polishing

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Figs 20a to 20e Glycerin gel was applied and light cured, followed by excess material removal. Figs 21a to 21c Flowable material injection on the posterior teeth. Fig 22 Polishing of the interincisal embrasure spaces.

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Figs 23a to 23c Finishing sequence of the buccal surfaces. Figs 24a to 24d Postoperative intraoral views.

paste was the last step to obtain a highly polished surface (Figs 23a to 23c). After static and dynamic occlusion is verified, the same finishing process is applied on the posterior teeth.

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A mutually protected occlusion with anterior and canine guidance without interferences on excursive movements was obtained (Figs 24a to 24d). The treatment outcome extraorally is presented in Figs 25 and 26.

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Figs 25a to 25d Postoperative extraoral views. Fig 26 Postoperative portrait photograph.

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CONCLUSION The injection technique, incorporating nanohybrid flowable composite materials with improved physical and optical properties, is a novel treatment modality for minimally invasive full-mouth rehabilitations. The combination of traditional prosthodontic and occlusal concepts with the injection technique facilitates esthetically and functionally pleasing outcomes. Clinical studies are necessary to evaluate long-term success.

REFERENCES 1. Vailati F, Gruetter L, Belser UC. Adhesively restored anterior maxillary dentitions affected by severe erosion: Up to 6-year results of a prospective clinical study. Eur J Esthet Dent 2013;8:506–530. 2. Blatz MB, Vonderheide M, Conejo J. The effect of resin bonding on long-term success of high-strength ceramics. J Dent Res 2017 Sep 1:22034517729134 [Epub ahead of print]. 3. Schlichting LH, Resende TH, Reis KR, Magne P. Simplified treatment of severe dental erosion with ultrathin CAD-CAM composite occlusal veneers and anterior bilaminar veneers. J Prosthet Dent 2016;116: 474–482.

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4. Terry DA. Restoring with Flowables. Chicago: Quintessence, 2015. 5. Cohen M (ed). Interdisciplinary Treatment Planning: Principles, Design, and Implementation. Chicago: Quintessence, 2008. 6. Moreno-Hay I, Okeson JP. Does altering the occlusal vertical dimension produce temporomandibular disorders? A literature review. J Oral Rehabil 2015;42:875–882. 7. The Glossary of Prosthodontic Terms, ed 9. J Prosthet Dent 2017; 117(5):1–105. 8. Fradeani M, Barducci G, Bacherini L. Esthetic rehabilitation of a worn dentition with minimally invasive prosthetic procedure (MIPP). Int J Esthet Dent 2016;11:16–35. 9. Edelhoff D, Schweiger J, Prandtner O, Trimpl J, Stimmlmayr M, Guth J. CAD/CAM splints for the functional and esthetic evaluation of newly defined occlusal dimensions. Quintessence Int 2017;48:181–191. 10. Blatz MB. Long-term clinical success of all-ceramic posterior restorations. Quintessence Int 2002;33:415–426. 11. Blatz MB, Sadan A, Kern M. Resin-ceramic bonding: A review of the literature. J Prosthet Dent 2003;89:268–274. 12. Chapman LJ, Burgess JO, Holst S, Sadan A, Blatz MB. Precuring of self-etching bonding agents and its effect on bond strength of resin composite to dentin and enamel. Quintessence Int 2007;38:637– 641. 13. Hyun HK, Christoferson CK, Pfeifer CS, Felix C, Ferracane JL. Effect of shade, opacity and layer thickness on light transmission through a nano-hybrid dental composite during curing. J Esthet Restor Dent 2017;29:362–367. 14. Ilie N, Rencz A, Hickel R. Investigations towards nano-hybrid resinbased composites. Clin Oral Investig 2013;17:185–193.

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Esthetic Rehabilitation of an Edentulous Arch Using a Fully Digital Approach

Tae Kim, DDS1 Fabiana Varjão, DDS, MS, PhD2 Sillas Duarte, Jr, DDS, MS, PhD3

Associate Professor and Section Chair, Removable Prosthodontics, Division of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 2 Assistant Professor, Division of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 3 Associate Professor and Chair, Division of Restorative Sciences, Director of the Advanced Program in Operative Dentistry, Herman Ostrow School of Dentistry, University of Southern California, Los Angeles, California, USA. 1

Correspondence to: Dr Tae Kim, Division of Restorative Sciences, Herman Ostrow School of Dentistry, University of Southern California, 925 W 34th Street, DEN 4365, Los Angeles, CA 90089-0641, USA. Email: [email protected]

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Figs 1a to 1c The patient presented to the clinic with dental implants placed 6 months earlier. She was requesting new maxillary restorations. Fig 2 The provisional complete denture was relined with soft denture liner.

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digital workflow can provide a more predictable and reliable treatment sequence for the rehabilitation of edentulous patients. Using digital technology, it is possible today to reduce the number of

appointments and provide comfort to the patient. This article describes the sequence for an implant-supported full-arch zirconia fixed dental prosthesis fabricated using a fully digital workflow.

Patient’s First Appointment: Intraoral Digital Scanning and CBCT Fig 3 Four scan bodies on four implants in place before scanning with 3Shape (Trios).

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Figs 4a to 4c Intraoral digital scanning was performed using Trios. Figs 5a and 5b Intraoral digital scan of the maxillary and mandibular arches. Figs 6a and 6b Panoramic digital images from iCat machine. Figs 7a to 7c Cone beam computed tomography (CBCT) images.

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After Patient Was Dismissed: Intraoral Scans and CBCT Files Sent Electronically to Dentca

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Figs 8a to 8c CBCT image was overlaid and matched with intraoral scan image using Dentca SW. This digital procedure provides the appropriate vertical dimension of occlusion and centric relation position of maxillary and mandibular digital impressions. Figs 9a to 9c Position of maxillary implants and relationship with mandibular teeth. Figs 10a to 10e Automatic maxillary teeth setup related with opposing teeth was performed (Dentca SW). A 3D-printed prototype was then generated.

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Figs 11a to 11g T bars were digitally generated (Dentca SW) and individually customized hexed bar-abutments fitted to individual implants.

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Figs 12a to 12f See-through overlaid design relationship between the digitally designed T bars and digital teeth setup. Figs 13a to 13c The mesh images of T bars sent for milling.

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Patient’s Second Appointment: T Bar Placement and Wash Impression

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Fig 14 Four individual T bars were placed and torqued at 30 Ncm. Fig 15 After screw tightening, the screw access holes were filled with spacer (temporary light-cured filling). Fig 16 A wash impression was taken with a washing tray to ensure correct positioning of the T bars for fabrication of the new digital design of the final zirconia restoration. Fig 17 A new bite registration was taken over the washing tray. This procedure will generate the new occlusion of the final zirconia restoration. Fig 18 A prototype of the final restoration in the patient’s mouth. Fig 19 Photograph of patient with the prototype.

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Fig 20 Design of final restoration using wash impression and bite registration provided (Figs 16 and 17). Figs 21a to 21d Digital design of final zirconia restoration. Figs 22a and 22b Full zirconia restoration with staining completed.

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Patient’s Third Appointment: Delivery of Implant-Supported Full-Arch Zirconia Fixed Dental Prosthesis

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Figs 23a and 23b Prototype was removed for cementation of two anterior bars and placement of two posterior retaining screws. Fig 24 Temp-Bond (Kerr) was used to cement the two anterior bars. Fig 25 The two posterior retaining screws were placed and torqued at 30 Ncm. Figs 26a to 26c Retaining screws (shown in purple).

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Fig 27 Full zirconia restoration in centric relation position. Fig 28 Full zirconia restoration in laterotrusion. Figs 29a and 29b Final outcome.

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Stefano Inglese, CDT

via Romolo Tranquilli, 15, 67057 Pescina (AQ), Italy. Email: [email protected]

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Emergence Profile: Relation Between Morphology, Biology, and Esthetics

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sthetics in dentistry involves many aspects: morphological and optical aspects, functional aspects in relation to shape and how they affect esthetics, and biological integration. In QDT 2014, I briefly presented some morphological and optical factors and how they affect the final appearance of teeth and restorations.1 The present article analyzes biological aspects regarding the relation between the tooth’s cervical emergence profile and gingival soft tissue, and how they influence the final esthetic outcome of our restorations. These are concepts that should be applied during laboratory procedures in order to create restorations that respect and preserve biological structures as well as reduce damage to them. Observation of the cervical third of the natural tooth helps us understand the emergence profile, which devel-

ops from the cementoenamel junction. The marginal gingiva and papillae form and levels reveal the effect of the emergence profile on the shape and stability of the soft tissue. We also can understand the relation, the balance, and the harmony that exist between the tooth and gingiva. We can distinguish between: • Subgingival emergence profile, which is responsible for support and stability of soft tissue. • Supragingival emergence profile, which is responsible for protection of soft tissue. We know that hard tissue supports soft tissue. By way of the tooth anatomy of the emergence profile in the cervical third, we can design and drive the gingiva where and

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Observing the natural teeth in relation to the gingival soft tissue should be an everyday practice to train our brain to better perceive and improve our ability to emulate what nature offers us today.

how we want—naturally—in relation to the quantity and quality of soft tissue, reaching harmony and stability. Only in this way can esthetics and a natural appearance be guaranteed. Pink and white esthetics should blend well together, and the former should support the latter in perfect balance. It is important not to allow our fantasy and imagination to

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change what already exists. We should simply try to emulate what nature offers us today, no more. Materials and technology are just tools. Digital systems, in particular, when used without knowledge, experience, ability, and sensibility, can become dangerous to the biology and therefore to the patient. In all cases, first we need to use our head, our hands, and our heart.

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Emergence profile emulation in wax: Through the morphology in the cervical third and transitional lines, we can manage the design of gingival soft tissue.

EMERGENCE PROFILE IN WAX-UP In these wax copings we can see how the emergence profile changes from the distal to the mesial of the tooth in order to create a natural form and level of the gingival contours and papillae, as well as establish the correct position of the gingival zenith. The anatomy of the restoration in

these areas will determine the final appearance of the dentogingival esthetics. Overcontour produces apicalization, while undercontour produces coronalization of marginal gingiva. Working with this concept, we can shape the soft tissue around the restoration as it occurs in nature. In the same way, transitional lines and interproximal morphology affect the form, dimension, and level of the papillae.1–6

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Emergence profile of wax coping in relation to the soft tissue of the master cast. The appropriate shape and interproximal triangular space allow the papillae to grow coronally until they completely fill the black hole, as we can see in this clinical case at (left) 1 month and (right) 4 years after cementation.

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Supragingival emergence profile and protection of marginal gingiva.

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Undercontoured

Overcontoured

There are three labial contour situations: 1. Undercontoured: The marginal gingiva is not protected, due to chemical or mechanical action, from mechanical stimulation of food during eating or brushing during hygiene. 2. Overcontoured: The marginal gingiva is hyper-protected, because of the lack of stimulation and automatic cleaning, causing accumulation of residual food and bacterial plaque. 3. Normal contour: The marginal gingiva is protected and stimulated correctly. This is the situation that needs to be reproduced in our restorations.5–8

3 Normal contour

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Correct reproduction of gingival soft tissue (Gingifast Rigid, Zhermack) in the laboratory.

Verification of cervical contours and interproximal contact areas on the solid cast.

Correct and precise reproduction of artificial gingiva is important in order to have a reference for fabricating appropriate subgingival and supragingival emergence profiles of our restorations. Then by fitting restorations on a solid cast, the cervical anatomy can be verified and optimized.

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www.pdflobby.com INGLESE Precision of the marginal closure of a restoration must be maintained from the waxing until the last polishing—and through all intermediate laboratory procedures.

MARGINAL CLOSURE Marginal precision in the preparation finish line is also important in order to (1) protect the dental structure, (2) avoid creating horizontal overcontours with consequent apicalization of the gingiva, and (3) reduce the quantity of cement exposed toward the soft tissue. A large marginal gap means large cement exposure, which is not healthy for the gingiva, especially when the marginal closure of restorations is located subgingival or interproximal and cement exposed cannot be polished well.

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We should obtain and maintain the marginal precision during all subsequent laboratory and clinical steps. It is possible to extend our precision even further using magnification systems. With magnification we enter another world—we can see what previously was hidden—and this requires us to change our working protocols completely. Clearly, time and patience are needed to master new and continually evolving methods and applications.

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Initial situation: Undercontoured cervical profiles are insufficient to protect the marginal gingiva.

The new emergence profiles and labial contours of the restorations in relation to the soft tissue of the solid master cast.

CASE IN POINT This is a typical case in which acid action has caused undercontoured labial profiles that are no longer able to protect the marginal gingiva from mechanical stimulation. By restoring the anterior segment with six veneers (e.max

Press and e.max Ceram, Ivoclar Vivadent), reshaping the axial labial contours, and with the correct emergence profile in the cervical third, the health and appearance of the marginal gingiva were transformed completely, harmonizing the esthetics of the hard and soft tissues.

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www.pdflobby.com INGLESE

Harmony with the lips is a result of the correct labial profiles and three-dimensional position of the incisal edges.

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www.pdflobby.com Emergence Profile: Relation Between Morphology, Biology, and Esthetics

Veneers fitted on the solid cast. Contour, volume, dimensional proportion, and dental axis are optimized. The dominance of the central incisors highlights the three-dimensionality of the dental composition.

Gingival and dental esthetics must support each other. The cervical third of the restorations drives and reshapes the gingiva for a pleasant design and appearance.

One year after cementation, the improved condition and appearance of the gingiva are evident. Of course, the shape of the teeth was optimized by the six veneers, but the soft tissue contributes to the overall esthetics. Func-

tion, incisal edge position, and color in all its dimensions are also important factors that balance and harmonize the restorations with the lips, face, and emotion of the patient.

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www.pdflobby.com INGLESE

Patient before treatment.

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After treatment: Harmony between the new smile design and somatic and emotional characteristics of the patient.

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CONCLUSION

ACKNOWLEDGMENTS

Dental esthetics always must be supported by gingival esthetics, and vice versa. Any tooth defect or gingival defect compromises the final appearance of the smile. The morphology of the cervical third greatly influences the gingival design. Only through knowledge, experience, and constant practice can we improve our confidence to perceive and reproduce correct emergence profiles. The marginal precision of restorations is also responsible for the health and stability of the soft tissue. It is fundamental to develop clinical and technical work protocols that are adequate to reproduce precision and, above all, to maintain it from the impression, during the laboratory procedures, and to the final cementation of restorations. Scientific and dental technology knowledge, accompanied by strong teamwork, are other factors essential for successful dental restorations.

A big thanks to Dr Nuria Otero for the great clinical work of the case shown in this article.

REFERENCES 1. Inglese S. Tooth morphology, optical phenomena, and esthetic perception. Quintessence Dent Technol 2014;37:158–171. 2. Bichacho N. Achieving optimal gingival esthetics around restored natural teeth and implants. Rationale, concepts, and techniques. Dent Clin North Am 1998;42:763–780. 3. Bichacho N. Cervical contouring concepts: Enhancing the dentogingival complex. Pract Periodontics Aesthet Dent 1996;8:241–254. 4. Su H, Gonzalez-Martin O, Weisgold A, Lee E. Considerations of implant abutment and crown contour: Critical contour and subcritical contour. Int J Periodontics Restortive Dent 2010;30:335–343. 5. Inglese S. Customized treatment for esthetic success: A case report. Quintessence Dent Technol 2012;35:211–212. 6. Inglese S. Aesthetic Dental Strategies: Art, Science, and Technology. Milan: Quintessence, 2015: 9,60,92–93,145–146,158,166–167, 176–177,209,216–218. 7. Kissov HK, Todorova BP, Popova EV. Correlation between overcontouring of fixed prosthetic constructions and accumulation of dental plaque. Folia Med (Plovdiv) 2001;43:80–83. 8. Morrow RM, Rudd KD, Eissmann HF. Laboratory Procedures, vol 2. St Louis, MO: Mosby, 1980:140–146.

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Esthetic Restoration with Ceramic Veneers in a Case of Altered Passive Eruption: The Appropriate Choice of Materials Is Key

Davide Bertazzo Dental Technician Via Eccettuato 7/A, 15033 Casale Monferrato, Italy. Email: [email protected], www.bertazzolab.it

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eramic veneers adhesively cemented and limited to the enamel represent today’s treatment of choice for minimal correction of the shape and color of teeth. They are a conservative solution for preserving tooth structure and have shown a high percentage of success over time, ranging from 93% to 96% at 15 years1 and 10 years,2 respectively. The purpose of this article is to underline the importance of the characteristics of the materials to be used in the reconstruction, which should be chosen appropriately and not casually, thus making the materials compatible to the treatment plan. Particular attention should also be paid to the planning phases and the interaction between the team members. Through proper protocols, such phases will contribute to guarantee the success of the restoration, not only from an esthetic point of view but also for its duration over time.

ALTERED PASSIVE ERUPTION Altered passive eruption (APE) is a clinical situation in which patients present excessive gingival display. Frequently, as in the case illustrated in this article, APE is associated with the presence of short and unesthetic crowns. To recreate the right balance for the reconstruction, a surgical procedure must first be performed to reestablish the proper biologic width and then to correct the shape of the natural teeth hidden by the excess soft tissue. In the case described herein, the teeth will have to be lengthened both apically and coronally. By reestablishing harmony in shape and proportions, the final result will strike the right balance between biology and esthetics.3,4 Clinical studies and literature determine the success or failure of a technique and guide us toward correct application methodology. Our task is to observe and study the teeth from their depths, examine their relationship with other structures, and study how they interact with restorative materials—not only during function or parafunction, but also, for instance, after traumatic events5 or abrasion processes (Fig 1). One of the most important treatment phases is the careful analysis of the primary stone cast—better if supplied with the mounting and setting of the articulator with the centric relation line of waxes and the dynamic facebow—to assess in perfect synergy the wear and tear of the veneers, precontacts, interferences, abrasion areas, as well

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as the Angle Class, overbite, overjet, general symmetry of the two arches, and inclination of the axis of every tooth. Abrasion, mainly owing to mechanical procedures6 and erosion due to chemical processes, is difficult to evaluate and assess directly in the oral cavity. As is well known, the involuntary grinding of teeth7 is a fundamental risk factor in abrasion of the tooth enamel8 as well as materials used in restorations.9 Bruxist patients, developing uncontrolled forces up to 10 times greater than normal mastication forces,10 cause restorations to break with high frequency. The appropriate choice of restoration materials in these patients, as in every case, is required.

RESTORATIVE MATERIALS The state-of-the-art microhybrid composites, with their esthetic and mechanical qualities—improved considerably thanks to filler technologies11—represent an excellent alternative to dental ceramic for both anterior and posterior restorations.12,13 However, their limitations lie in their lower resistance to wear and tear under extreme or stressful conditions.14,15 Clinical studies have demonstrated that over time, composite veneers can display changes or modifications of their surface quality with a frequency six times higher than ceramic veneers.16,17 Another significant difference that affects the final result is attributable to the stratification techniques used for restorations made with composite and ceramic materials. The fact that the ceramic mass can be worked when wet allows penetration for obtaining subtle and delicate effects. The stratification technique of composite, by its very nature and because of its plasticity, is completely different. The shades and effects that can be produced are proportional to the dexterity of the professional layering and mixing the different strata of the material to be polymerized. This should be done without losing control of the shape or creating unesthetic gaps between the various strata. Correlating qualities such as flexural resistance and elastic modulus (Young’s modulus), we are able to calculate the fragility of a material. Unlike metal restorations, dental ceramics are subject to breakage when they reach their elastic limit, even with an allowance for elastic deformation. This characteristic classifies ceramic as a fragile material compared to metals, which are plastically deformable.18 Glass-ceramics stratified and sintered on refractory dies or with the platinum sheet technique, whether or not

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Fig 1 Our role is to study and copy nature. (Courtesy of Alessandro Conti, DDS.)

their vitreous phase had been strengthened by leucitebased crystals, feldspar, or fluorapatite, have achieved satisfying results with an excellent chromatic stability, thanks to very thin layers. By directing the light on the underlying tissues and the gingiva, the unesthetic “umbrella” effect described by Pascal Magne can be avoided, taking advantage of the characteristic translucence of the material at its best.1,19 The weak point of glass-ceramics is their substantial fragility during try-in and the traction tension to which they are subjected following contraction of the volume during the hardening process with the composite cement. This vulnerability is represented by the flexural resistance of glass-ceramics, which ranges between 70 and 120 MPa. The correct color of the cement material also is an important consideration, for if underestimated it can lead to failure by lowering of the quality of the final restoration as light filters through the translucent material. With the evolution of Empress 2 to IPS e.max Press (Ivoclar Vivadent), it is possible to utilize a glass-ceramic whose glassy matrix is filled by around 70% lithium disilicate crystals,20 thereby obtaining a material with flexural resistance values ranging from 350 to 400 MPa.21 The re-

sults in terms of precision are adequate using either the press technique or CAD/CAM.22

CASE PRESENTATION A 24-year-old patient came to the office for consultation on improving the esthetics of her smile (Fig 2). She did not like the shape of her teeth, finding them too short and lacking in proportion (Fig 3a). Full-mouth radiographs confirmed the diagnosis of APE Type 1 subtype B, indicating that surgery would be the first step of treatment to achieve new tooth proportions (Fig 3b).23 The analysis of the primary stone casts showed a degree of abrasion with protrusive canine guidance paths involving the incisal edge of the teeth in need of restoration. This led the team to choose a veneering material with a high flexural strength and with mechanical characteristics sufficient to guarantee longevity of the functional guidance restoration (Fig 4).

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3a

3b

4

Fig 2 Baseline lateral views for evaluation of abrasion and demonstrating proportion of lips and teeth. Fig 3a Baseline extraoral photos for correlation of the patient’s face, age, and personality. Fig 3b Baseline radiographs. Fig 4 Stone cast for evaluation of abrasion and for restoration of functional guides in wax.

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5a

5b

Fig 5a New esthetic guide lines. Fig 5b New tooth shapes determined using the Digital Smile Design (DSD).

Evaluation for First Wax-up and Mock-up The new plan was designed (by Dr Alessandro Conti) based on an analysis of the shapes, the new guide lines, and the positions of the teeth using the Digital Smile Design (DSD, Christian Coachman), as well as taking into account other esthetic parameters (Fig 5). Lips, for instance, play a fundamental role in their support function and the spatial projection of the teeth themselves (Fig 6). The smile line differs between masculine and feminine anatomy, with the latter more curved in the inferior lip, and higher and more parallel to the incisal superior line compared to the mascu-

line one, which is nearly always shorter and straighter. In this case an effort had to be made to achieve a restoration with a high-low-high trend in the anterior teeth.24 After the evaluation, the dental technician developed the clinical plan with a first wax-up for initial esthetic analysis but especially to establish the gingival levels during the surgical resetting phase. The wax-up was prepared with the addition of esthetic wax on a white extra-hard stone cast (Fujirock EP, GC Europe) including a gingival portion that would simulate the apical lengthening of the crowns. Less attention was paid to the details of the new shapes in this wax-up phase, placing more importance on the surgical phase (Fig 7).

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www.pdflobby.com BERTAZZO Fig 6 New proportion of lips and teeth (compare to baseline in Fig 2).

6a

6b

Fig 7 First and second wax-ups. (Top) Final wax-up is more accurate and precise. (Bottom) First stone cast and first wax-up for surgical procedures.

7

Fig 8 Surgical procedure phases. (Courtesy of Roberto Rossi, DDS, MScD).

8

Through a transparent silicone mask, the mock-up with the dual composite (Protemp, 3M Espe) was printed on the

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patient, followed by the resective surgical procedures (performed by Dr Roberto Rossi) shown in Fig 8.

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9b

Figs 9a and 9b Second mock-up with final tooth shapes obtained through the second wax-up for evaluation.

Second Mock-up One year later, when the tissues had reached maturation, a new series of stone casts were made, again in white extrahard stone (Fujirock EP). This was followed by a new, more precise esthetic wax-up, taking into account the shapes and the correlation between the face, age, and personality of the patient. Particular attention was directed to the po-

sitioning of the apex of the distal third of the maxillary central incisors in order to give a symmetrical design to the gingival edge with a pleasing esthetic result (Fig 9a). The second mock-up was designed (by Dr Conti) once again through a silicone mask and a dual composite, completing it all with a series of intra- and extraoral photographs and video for a dynamic evaluation of the new plan with the patient (Fig 9b).

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Fig 10 The microscope is necessary for the clinical and laboratory phases. (Right, from top) Baseline, 1 month postsurgery, and after minimally invasive preparation.

After the patient accepted the mock-up and agreed to the plan, the team went on to the next phase of preparation, once again with the aid of a microscope (Zeiss OPMI Pico). Use of the microscope by the dental technician is necessary to guarantee success using a minimally invasive approach with a defect-oriented preparation,25 together with quality adhesion through a correct cementation protocol and perfect isolation of the operative field,26,27 as well as precision in the construction of the indirect restorations (Fig 10).

Veneer Fabrication For the construction of the veneers, two different master stone casts were made. The first was made using the Zeiser technique (Zeiser Sockelplatten, Zeiser Dentalgeräte GmbH), sectioned with removable dies. The second was made in polyurethane resin, nonsectioned (ExactoForm, Bredent). The wax-up for the construction of the veneer cores was carried out on the sectioned master cast with execution and control of the preparation finishing lines as well as the successive adaptation under the microscope (Zeiss Stemi 1000). The anatomy of the shapes in the ceramic phase was performed on the nonsectioned master cast, creating each veneer individually and compar-

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ing each with the original wax-up of the mock-up approved of by the patient, reprinted on the stone cast specifically for the ceramic phase (Fig 11). All this was done to better concentrate attention on the detail and particulars and above all to try to replicate with greater ease the shapes of the second wax-up/mock-up, which had been obtained with great effort, taking care not to change the personality of the teeth to be reproduced. The choice of the core material is of fundamental importance for the final result and luminosity. The stratification technique must resemble nature itself as much as possible and, in so doing, try to imitate dental structures in relation to the age of the tooth to be replicated. The six veneers were fitted with the press technique by the viscous sliding of the material, using a core LT (Ivoclar Vivadent). LT is a pure dentin core with a good fluorescence that requires the cutback technique (Figs 12 and 13). To ensure appropriate luminosity to the final restorations and to avoid a possible decrease in value during multiple firing cycles, A1 shade was used to yield 70% of the core volume and 30% of the ceramic stratification sintered (over the core itself). This case required reproduction of a young tooth that was slightly opaque but with in-depth luminosity, desaturating the dentin to make it progressively more translucent in the incisal third. In this area the light absorption mass, or colored translucent mass, was ap-

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13

12

14

Fig 11 Second master cast in polyurethane resin. (From left) Minimally invasive preparation, comparison of wax-up and lithium disilicate core, and lithium disilicate cores (LT A1) adapted on model. Fig 12 Stratification phase. Fig 13 Wax ready to be pressed. Fig 14 Ceramic phases (from left): dentin and dentin desaturation, opal effects, and absorption masses.

plied during the layering so that the light could penetrate the tooth more rapidly28 (Fig 14). After the first bake, the effects were heightened in a targeted manner by fixing the Essence colors and shades (Ivoclar Vivadent) in an oven at low temperature. This was done because in a ceramic with a low point of fusion, the best result is obtained with a minimum number of firings near the final point of sintering (705°).

To complete the process, the Enamel and Neutral (60% to 40%) filter was applied to condition the translucence level in the incisal area, completing the final anatomy of the veneers. A small amount of dentin was inserted in the proximal areas with a mix of orange opaque dentin and translucent cervical (70%-20%-10%) to stop the light in this area (Fig 15).

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Fig 15 Ceramic phases (from left): light absorption masses and Enamel filter. Fig 16 Tools used in finishing and polishing phases.

The finishing phase was done with diamond burs cooled by water, starting with the macro surface weaving with a pronounced convexity and concavity to reproduce a young tooth, followed by micro surface weaving with Retzius lines and microgrooves to allow better light reflection. The transition lines, in keeping with the parameters and the three Kuwata planes, achieved a three-dimensional effect.1,29 The final bake and glazing was obtained by very delicately applying a small quantity of glaze with a brush. However, this was preceded by the mechanical polishing phase carried out with rubber cups, felt, and diamond paste (Figs 16 to 18).

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Cementation Adhesive cementation calls for a very strict protocol to be observed for isolation of the operating field and the adhesion procedures (Fig 19). A 4th-generation total-etch adhesive (OptiBond FL, Kerr) and a microhybrid composite as the cementing material were heated to 52˚C for the cementation. Figure 20a to 20e show the intraoral results and Figs 21a and 21b the before-and-after extraoral evaluation.

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18

19

Fig 17 Final veneers. Fig 18 Stratified lithium disilicate veneers adapted on uncut master cast. Fig 19 Adhesion phases (from left): isolation, etching, rinsing, bonding, cementation.

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20b

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20d

Figs 20a to 20e Extraoral photographs and radiographs of definitive restorations. Figs 21a and 21b Extraoral evaluation of final outcome (a) and preoperative view (b).

20e

21a

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21b

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Fig 22 Successful outcome; satisfied patient.

CONCLUSION Esthetic dentistry is well established today. It aims to create dental restorations that are perceived by patients as esthetically pleasing. Restorations with ceramic veneers represent one of the most demanding challenges but also one of the most satisfying in this respect. The clinical result is influenced by several factors that must be taken into consideration while working as a team to guarantee the success of the end result.

Correct planning through specific protocols, preparing teeth with a minimally invasive approach, with an appropriate final cementation technique together with precision in the construction of the dental fittings and an impeccable choice of materials, are all necessary to guarantee a professional result as well as the health and satisfaction of every patient (Fig 22).

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ACKNOWLEDGMENTS My very special thanks to Dr Roberto Rossi and Dr Alessandro Conti for making me a part of this important project. A thank you to all the professionals with whom I collaborate for their trust, an indispensable factor in our line of work. And a special word of thanks to Quintessence for granting me this opportunity.

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14. Tyas MJ. Correlation between fracture properties and clinical performance of composite resins in Class IV cavities. Aust Dent J 1990; 35:46–49. 15. Schlichting LH, Stanley K, Magne M, Magne P. The non-vital discolored central incisor dilemma. Int J Esthet Dent 2015;10:548–562. 16. Gresnigt MM, Kalk W, Ozcan M. Randomized clinical trial of indirect resin composite and ceramic veneers: Up to 3 year follow-up. J Adhes Dent 2013;15:181–190. 17. Moura FR, Romano AR, Lund RG, Piva E, Rodrigues Júnior SA, Demarco FF. Three-year clinical performance of composite restorations placed by undergraduate dental students. Braz Dent J 2011; 22:111–116. 18. Kappert HF. Dental materials: New ceramic systems. Academy of Dental Materials Proceedings Transactions 1996;9:180–199. 19. Fradeani M, Redemagni M, Corrado M. Porcelain laminate veneers: 6- to-12-year clinical evaluation—A retrospective study. Int J Periodontics Restorative Dent 2005;25:9–17. 20. Edelhoff D, Spiekermann H, Rùbben A, Yildirim M. Kronen- und Brückengerüste aus hochfester Presskeramik. Quintessez 1999;50: 177–189. 21. Pospiech P, Kistler ST, Frasch C, Rammelsberg P. Clinical evaluation of posterior crowns and bridges of IPS Empress 2: Preliminary results after one year [abstract 1610]. J Dent Res 1999;78(special issue):307. 22. Rinke S, Behi F, Hüls A. Fitting accuracy of all-ceramic posterior crowns produced with three different systems [abstract 997]. J Dent Res 2001(special issue);80:651. 23. Garber DA, Salama MA. The aesthetic smile: Diagnosis and treatment. Periodontol 2000 1996;11:18–28. 24. Hidaka T. Solutions for Dental Esthetics: The Natural Look. Tokyo: Quintessence, 2008. 25. Massironi D, Pascetta R, Romeo G. Precision in Dental Esthetics: Clinical and Laboratory Procedures. Milan: Quintessence, 2007. 26. Brentel AS, Ozcan M, Valandro LF, Alarca LG, Amaral R, Bottino MA. Microtensile bond strength of a resin cement to feldspathic ceramic after different etching and silanization regimens in dry and aged conditions. Dent Mater 2007;23:1323–1331. 27. Edelhoff D, Liebermann A, Beuer F, Stimmelmayr M, Güth JF. Minimally invasive treatment options in fixed prosthodontics. Quintessence Int 2016;47:207–216. 28. Ubassy G. Shape and Color: The Key to Successful Ceramic Restorations. Chicago: Quintessence, 1993. 29. Kataoka S, Nishimura Y. Nature’s Morphology: An Atlas of Tooth Shape and Form. Chicago: Quintessence, 2002.

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