Volume 6, Issue 10
Published by AEGIS Communications
Predictable Techniques for a Complete Ceramic Rehabilitation Using Lithium Disilicate
A well-planned systematic approach can improve collaboration between dentists and laboratory technicians and produce better patient results.
The outcome of every case, no matter how complex or straightforward it is, depends upon the synergy between the three parties involved-the dentist, the laboratory technician, and the patient. When the dentist and technician have a long-standing working relationship based on a shared desire for delivering excellent dental restorations, it contributes directly to better communication between them and to the esthetic and functional success of the finished work.
Such collaborations characteristically have an understanding that goals for the completion of a complex restorative case must be delineated in advance. Therefore, identifying the patient's needs and desires is a priority addressed during a comprehensive examination that begins with a preclinical interview. Additionally, such dentist-technician teams inherently want to create a natural smile that does not distract the eye, conserving as much natural tooth structure as possible. They also spend time selecting materials and using techniques that ensure the longevity of the completed restoration(s).
The authors have developed a systematic approach for the dental restoration process, one that leaves nothing to chance in order to increase the likelihood of realizing consistently predictable results. Each step in the entire process is planned, with either the dentist or technician responsible for the ultimate result of that aspect of the case. If there is ever a problem or discrepancy in the process, the respective individual is accountable and can implement the necessary adjustments or corrections.1
1. The Diagnostic Evaluation
During the comprehensive diagnostic examination, the dentist spends time with the patient in a preclinical interview to discuss his or her chief concerns and priorities.2 Complete periodontal charting, comprehensive clinical examination, and a thorough temporomandibular joint (TMJ) evaluation is conducted. Every case is evaluated using study models mounted in centric relation (CR), as well as a complete series of diagnostic radiographs and photographs.
2. Smile Design Consultation
If the patient's goals are congruent with the completed treatment plan, the patient is appointed for the smile design consultation. It is during this time that computer imaging, direct composite mock-ups, or both will be used to involve the patient in the process and facilitate acceptance of the smile design plan.3
3. Esthetic Wax-Up Checklist
An important step in the process is the completion of the esthetic wax-up checklist, which the dentist provides to the laboratory technician in addition to other case information (eg, equilibrated, mounted study models; photographs; computer imaging) necessary to fabricate an ideal wax-up of the desired functional and esthetic final result.4,5Before the case is returned for prototype template fabrication, the technician can communicate with the dentist by e-mailing digital photographs to confirm that the wax-up satisfies all requirements.
4. Preparation Guides/Templates
The waxed models then can be used to fabricate very accurate templates that enable the patient's prototype restorations to become an exact replica of the waxed models. Preparation templates also are constructed from the waxed models before the patient arrives for the preparation appointment in order to facilitate precise tooth preparation with minimal tooth reduction.6
A rubber dam is used to isolate an entire arch when old restorations are removed and/or teeth require build-up using dentin-colored hybrid composite resin. Once the preparations are complete, multiple impressions are taken using a syringeable hydrocolloid and water-cooled hydrocolloid material. At least four impressions are taken for every case, including five or six full-arch impressions. The first impression is poured immediately with an ultra-fast setting stone (Snap-Stone, Whip Mix Corp, http://www.whipmix.com), which ensures that by the time all impressions are completed, a model is available for use in creating the provisional (ie, prototype) restorations.
6. Prototype/ Provisional Restorations
The provisional restorations are called prototypes because every effort is made to ensure that they replicate the desired outcome for the final restorations. Therefore, the authors advocate the use of an extremely durable provisional material, one that can be layered to achieve an esthetic result that rivals the final porcelain restoration.7
Then, all of the prototypes except for one central incisor are cemented or spot-bonded into place, and another final impression is taken to fabricate the trial-unit model, after which the remaining central incisor prototype is placed. The patient is dismissed and instructed to return the following week to reevaluate the prototypes. At that time, any necessary changes are made to the prototypes to satisfy doctor and patient requirements. When the patient accepts the prototypes, he or she signs a prototype approval form, and photographs of the prototypes, accurate impressions, and bite records are taken to begin the fabrication process.
Using bite records taken in CR at the predetermined vertical relation, the sectioned and trimmed die models and prototype models are mounted on a semi-adjustable articulator. All models are approved and mounted in the dentist's office, and the mounting accuracy is verified before sending the case to the laboratory. Three sets of models are provided for every case-mounted sectioned die models, solid die models, and mounted prototype models. The dentist also may write a detailed prescription specifying the esthetic, occlusion, material, and other parameters so the technician is aware of any requirements for fabricating an ideal case.
8. Trial Units
The laboratory technician uses the trial-unit model to fabricate a trial unit of a single central incisor with the desired shade, texture, translucency, and shape. When the patient returns for the trial-unit appointment, the dentist removes the provisional restoration for the single central and places the trial unit with try-in gel for patient approval. Once the patient approves the trial unit, he or she signs a trial-unit acceptance form. This trial unit is not used in the final case, but provides assurance that the patient will not change his or her mind and reject the case because of the shade and allows the fabrication process to proceed.
Using the prototype models as a guide, the technician now completes the restoration, as nothing has been left to chance. The solid model is used to confirm the fit and interproximal contacts of each unit. If there are any questions, the technician can communicate with the dentist via digital photography and e-mail to clearly and specifically detail any areas of uncertainty.
10. Verification/ Definitive Cementation
When the case is returned to the dentist's office, accuracy is confirmed with another unused solid model that was retained in the patient's case pan (eg, a hold-back model). Prior to insertion, the dentist confirms that the patient's occlusion and anatomy are ideal. When each of these steps is completed, it is extremely rare that the case is not cemented during the insertion appointment. Once the restorations are seated, the occlusion can be perfected, the porcelain is polished, and a hard acrylic nightguard is fabricated.
The final step in the complex restoration process is realizing the rewards associated with this type of treatment. In addition to the financial compensation that comes from the many hours of hard work, clinicians can take pride in knowing they have collaborated to create a ceramic reconstruction that will serve their patients for many years to come. The following case presentation illustrates how all of these steps are incorporated into actual clinical and laboratory protocol to culminate in exceptional restorative results when using a lithium disilicate material.
A 40-year-old man presented with the chief complaint of "dark-colored and severely worn front teeth" (Figure 1). The TMJ examination revealed stable joints, with no tenderness or discomfort upon heavy loading in CR. A thorough periodontal examination showed healthy tissue, with no significant bone loss or inflammation. His anterior teeth were worn significantly into the dentin, and there also was some significant enamel loss on the posterior teeth, but they were not symptomatic. There were no clinical or radiographic signs of decay.
Study models mounted in CR (Figure 2) revealed that most of the severe wear was restricted to the anterior teeth, since most of the posterior teeth exhibited minimal loss of tooth structure. The vertical dimension of the arches with the teeth in CR provided sufficient space to restore the anterior teeth in an ideal relationship.8,9
The accepted treatment plan included minimal preparation onlays and veneers for all teeth, except for the fixed partial denture to replace tooth No. 30. A lithium disilicate material (IPS e.max®, Ivoclar Vivadent, www.ivoclarvivadent.com) was chosen for the fabrication of the all-ceramic onlay and veneer restorations based on its esthetic qualities and durable, monolithic strength.10 The fixed bridge would be fabricated with a pressable ceramic (IPS e.max ZirPress, Ivoclar Vivadent) pressed over a zirconium framework.
The first step was to complete the smile design appointment, during which computer imaging was used to create an esthetic facsimile of the proposed reconstruction (Figure 3 and Figure 4). The patient requested that no metal be visible, but he also wanted a "natural" look for his age. He did not want extremely white teeth or an artificial appearance to his smile.
After the smile design appointment, the dentist completed the esthetic wax-up checklist, then sent it to the technician, along with photographs and the computer image, to create the complete wax-up at the desired vertical dimension. The technician allowed sufficient time to complete the detailed wax-up, incorporating not only the esthetics desired, but also ideal occlusion with carefully detailed anterior guidance and posterior centric stops (Figure 5 and Figure 6).10
Preparation & Provisionalization
The patient was appointed for 2 consecutive full days for preparation and provisionalization. During the first day, the entire maxillary arch was anesthetized with articaine and isolated with a rubber dam. All teeth were prepared using a silicone reduction guide, and all of the existing restorations and old bases were removed. After the old amalgam restorations were removed, the preparations were built up using a dual-cure composite (CosmeCore, Cosmedent Products Inc, http://www.cosmedent.com) and a dual-cure adhesive bonding agent (Clearfil® Liner Bond 2V, Kuraray America Inc, http://www.kuraraydental.com).
The posterior onlay preparations were completed, allowing 2 mm of occlusal reduction with a facial veneer preparation. The anterior 360° veneer preparations were conservative, with 1 mm of lingual reduction and minimal facial reduction, leaving enamel covering the facial surfaces (Figure 7). Prior to completing the preparations, teeth Nos. 4 through 6 were crown lengthened with electrosurgery (ie, the appropriate amount of bone was removed for proper biologic width after the impressions were taken).11
Six hydrocolloid impressions were taken-three with a syringeable bonding hydro and alginate material (Identic, Dux Dental, http://www.duxdental.com) andthree with reversible hydrocolloid (Slate, Dux Dental) in a water-cooled tray. One of the alginate-to-hydrocolloid impressions was poured immediately with an ultra-fast setting stone (Snap-Stone). The provisional restorations were fabricated on the stone model using templates made from the wax-up model and a layering provisional material (Radica®, DENTSPLY Prosthetics, http://www.ceramco.com) (Figure 8). The provisionals were spot-bonded in place using a resin cement (Insure yellow-red light, Cosmedent Inc).
The patient returned the following week for the postoperative check-up to verify the occlusion and esthetics of the prototype (ie, provisional) restorations. He was very comfortable and pleased with the esthetics of his new smile, so no changes were necessary (Figure 9 and Figure 10). Alginate impressions of both arches were taken, along with a bite record and digital photographs. After reviewing home care and flossing instructions as well as careful advice about how to eat with the temporary restorations, the patient was released and reappointed for a trial-unit try-in a few weeks later.
While the trial unit was being fabricated, the records obtained earlier were used to mount the models on a semi-adjustable articulator (Artex, Jensen Dental, http://www.jensendental.com) that had been calibrated with the technician's articulator so that the models were interchangeable. The final pinned die models and the models of the accepted provisional restorations were all interchangeable, which allowed the provisionals to be duplicated esthetically and functionally. Separate solid models also were included to aid in the fabrication process (Figure 11).
Evaluation of the Trial Unit
When the provisional restorations were placed, all but one central incisor was cemented, and a syringeable impression (Identic, Dux Dental) was taken. This tooth was then provisionalized, and the model was sent to the technician so one trial-unit veneer could be fabricated according to the patient's criteria for an esthetic but natural-looking restoration. To create the natural look that the patient desired, the HT BL3 shade IPS e.max Press ingot was selected. After waxing and pressing the veneer to full contour, the incisal portion of the veneer was cut back, and the internal color characteristics were developed with a layering material (IPS e.max) (Figure 12 and Figure 13).
The patient returned for the trial-unit appointment, and the provisional veneer was removed. The trial veneer was placed using a yellow-red light try-in gel (Prevue, Cosmedent Inc). The patient and dentist evaluated the color, translucency, anatomy, and surface texture, and decided to accept the trial unit (Figure 14). The patient signed a trial-unit approval form, indicating acceptance of the shade and agreeing to move forward with the full reconstruction using the trial as a guide. The dentist took a series of digital photographs of the trial veneer, adjacent to the appropriate shade tabs, and the provisional veneer was re-cemented. The technician used the trial unit to facilitate fabrication of the entire case, but did not use it as one of the final restorations.
When the completed case was returned to the dentist's office, a fourth solid model was used to confirm the fit and interproximal contacts (Figure 15 and Figure 16). The occlusion also was confirmed on the articulator prior to scheduling the patient for insertion. Once the dentist confirmed that the case fit the models created by his office and that the occlusion was correct for the mounted models, he confirmed that the technician followed the prescription appropriately.
Had there been a problem with the fit or occlusion when the case was delivered, the dentist would have accepted the responsibility for the error. However, when the system is followed properly, errors are rare. Using multiple impressions for multiple models helped eliminate mistakes, misfits, and remakes.
At the final insertion appointment, the entire arch was anesthetized, and the patient's maxillary provisionals were removed. The individual restorations were tried on dry for fit, then with try-in paste (Prevue yellow-red light). The patient accepted the esthetic try-in and signed the approval form prior to definitive cementation. Prior to cementation, all teeth were treated with a dentin-enamel primer (Liner Bond 2V, Kuraray America Inc) and bonding agent (Clearfil® PhotoBond, Kuraray America Inc). After all restorations were etched with hydrofluoric acid, they were seated with a resin cement (Insure yellow-red light). The lower arch restorations were inserted using a similar protocol.
After the cementation, the occlusion was perfected by equilibrating with a fine diamond wheel (Figure 17 and Figure 18). All margins and the adjusted porcelain were polished using porcelain polishers (Komet USA, http://www.kometusa.com).
For such a case to last predictably for years, the final occlusion must be ideal. Therefore, it was necessary to provide the patient with a protective nightguard (Figure 19), which he agreed to wear every night while sleeping to help protect the porcelain surfaces from wear and chipping. Even though the reconstruction process was long and intensive, the patient was delighted with the outcome (Figure 20, Figure 21, Figure 22, Figure 23) and said he would not hesitate to recommend this type of treatment to anyone who needed it.
To achieve a predictably successful result in a complex, all-ceramic reconstruction, adhering to a system of conscientiously developed steps can help eliminate the finger pointing that could occur in the event that problems arise. In more than 20 years of collaboration, the authors have developed a system that incorporates every step in the reconstruction process. Utilizing their systematic approach has ensured they deliver predictably acceptable results, both functionally and esthetically.
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About the Authors
Mike Malone, DDS, AAACD
Mike Bellerino, CDT, AAACD