Design and Management of the Worn Anterior Dentition: A Case Study With Porcelain Veneers and a Ceromer/Fiber-Reinforced Composite Framework
Written by Jeffery M. Rosenberg, DDS Monday, 31 December 2001 19:00
In today’s aesthetically oriented dental practice, a common motivator to seek aesthetic treatment is the worn dentition. Designing the final appearance to be in harmony with the smile, face, and function is challenging as the patient accommodates to the wear process and shorter, flatter teeth. In addition, selecting a durable, yet highly aesthetic material can be difficult, as many of the materials used today have a limited track record. Lastly, patients want conservative treatment and may be opposed to “aggressive” tooth preparation procedures.
To assist in creating a successful rehabilitation of the worn dentition, the cause for the clinical condition must be diagnosed, and orderly objectives set forth to re-establish and then maintain a functional and aesthetic result.
ANTERIOR PROTECTIVE GUIDANCE, REMOVAL OF INTERFERENCES
Research and clinical observation have shown an increase in parafunction caused by occlusal interferences.1 Most destructive are nonworking interferences. Close evaluation will reveal the majority of nonworking interferences occur with accelerated anterior tooth wear. Whether the interferences occur before wear or as a result of it has yet to be proven. Yet, the occlusal scheme should be stabilized prior to restoration.
Therefore, to rehabilitate an anterior worn dentition, evaluation and treatment of posterior interferences must occur first. This is accomplished through clinical examination and evaluation of facebow-mounted study casts. Study casts will show if simple occlusal equilibration will suffice or if a complex rehabilitation is necessary. Next, the lower incisal edge position must be set.2 This edge must be in harmony with the aesthetics of the lips (lower in particular), and be able to function with the lingual surfaces of the maxillary anterior teeth in centric relation and lateral, protrusive, and crossover excursions. This guidance should be protective of the posterior occlusion.
Treatment of the incisal edge position involves any of three modalities: recontouring, reconstructing, and/or repositioning.3 Today, most wear cases involve reconstructions with porcelain or composite lamination and recontouring. After setting the lower incisal edge position, the maxillary anterior teeth can be treated, followed by the mandibular posterior, and finally the maxillary posterior teeth.
Several factors are involved in determining the final maxillary anterior tooth designs4:
•Patient expectations and facial form
•A 75% to 80% width-to-length goal to establish the central incisors as the dominant teeth of the smile
•Determining if incisal length will come from adding to the incisal edge or lengthening the gingival tooth structure
•Evaluation of the midline and axial inclinations
•Golden proportion, teeth shown during a full smile to include the buccal corridor
•Evaluation of the gingival zenith, papillae, and ridge volume
•Existing color and proposed color.
A smile design checklist should be used to record each factor at an aesthetic examination appointment (see author’s note). Kodachrome (Eastman Kodak Co) slides should be taken to document the case and communicate during the lab phase of treatment. Computer imaging of the proposed changes should be made, if possible. These computer images can be used to communicate with the laboratory ceramist and others. Polaroid pictures of the face and smile are extremely beneficial. Taping up the Polaroids during tooth preparation provides a visual opportunity to begin “with the end in mind.” Many times, preparations are scrutinized up close, but the clinician may lose perspective of the final outcome. Referring back to these Polaroids during preparation greatly assists in staying on track. Impressions with well-extended borders should be made to wax-up the case and fabricate stents for control of tooth preparation and for the provisional restorations.
A 52-year-old male presented with significant wear of his anterior dentition. Tooth No. 8 had been lost because of trauma and was replaced with a failing resin-bonded bridge. The alveolar ridge was severely compromised (Figures 1 through 3). There was wear and crowding from teeth Nos. 22 through 27 (Figure 4). Ceramic gold bridges replaced teeth Nos. 4 and 19, and spanned to the adjacent teeth. The patient requested an improved aesthetic appearance without “grinding down” his front teeth.
Periodontal examination revealed generalized 2- to 3-mm probing with adequate attached tissue except in the area of tooth No. 8. The mandibular ranges of motion were 50 mm, 12 mm, and 12 mm with no joint restrictions or pain.
Radiographic and Kodachrome photographic examinations were performed. The computer was used to ascertain a projected treatment outcome.5 The patient had input on the tooth length, shape, and shade via the Image FX Program (Image FX Software Solutions, Inc). The computer imaging illuminated the need for increased ridge thickness in the area of No. 8 and comprehensive maxillary anterior treatment. The imaging “cemented” the treatment in the patient’s mind.
Impressions were made and casts were facebow mounted in centric relation on a semi-adjustable articulator. Evaluation of the mounted casts revealed nonworking interferences at teeth Nos. 2, 15, 17, 18, and 31 and the need for occlusal equilibration. The mandibular incisal edge of tooth No. 25 was positioned too far labially for recontouring or restoration. This tooth interfered with the proper replacement of tooth No. 8, as well. A spring aligner was fabricated from 0.036-inch stainless steel orthodontic wire and clear orthodontic resin.
A flowable composite resin (Revolution, Kerr Corp) was added to the incisal edges of teeth Nos. 6 through 11 on the study cast. The increased length permitted cuspid disclusion and established a 77% width-to-length ratio of the central incisors. The model was duplicated and 0.15-inch polystyrene splint material (Pearson Dental Supply Co) was adapted to the model. This splint was indexed against the posterior teeth, and would be used as a guide during tooth preparation and provisional fabrication (Figures 5 through 7).
|Figure 1. Pretreatment dentition. Note the worn dentition and mandibular crowding.||Figure 2. Lateral view showing incisal wear and ridge deformity.|
|Figure 3. Failing resin-bonded bridge with multiple diastemas.||Figure 4. Crowded mandibular anterior teeth with labialized tooth No. 25.|
|Figure 5. Revolution (Kerr Corp) added to create 77% width-to-length ratio on the central incisors, as well as proper disclusion.||Figure 6. Completed tooth modifications.|
|Figure 7. Occlusal stint used as a guide for tooth reduction and provisionals.||Figure 8. A 0.036 stainless steel orthodontic spring aligner.|
Pressed ceramic veneers (IPS Impress, Ivoclar Vivadent) were selected to be used on teeth Nos. 6 through 12. The pressed ceramic has a flexural strength of 23,000 to 24,000 psi, and a compressive strength of 180,000 to 190,000 psi is derived from the reduced size and improved distribution of the leucite crystals without reduction of the total crystalline content. The reduced abrasive surface (because of the smaller leucite fragments) of the pressed ceramic material offers an advantage in altering incisal and cuspid guidance, and the stability of the pressed ceramic allows for the ease of staining, glazing, and color alteration.6
Ceromer fiber-reinforced composite (FRC) frameworks have a high flexural strength of 10,000 Mpa, which is 10 times stronger than feldspathic porcelain, and rivals PFM restorations.7 Their modulus of elasticity is similar to dentin. These properties made it a logical choice as a framework to replace tooth No. 8. The strain of the occlusal forces would be evenly distributed within the abutment teeth, and the color and translucency of the framework would permit optimum aesthetics. Ceromers contain fine particle ceramic fillers of micro-meter size (0.04 µm and 1 µm), and are closely packed (75% to 80% weight) in an organic polymer matrix. The particle component creates a durable, polishable, repairable aesthetic material.
The combination of ceromer and a FRC framework seems ideal. These materials have been evaluated in single unit applications since 1989, but long-term clinical studies have yet to be conducted.
|Figure 9. Chamfer diamond used to accentuate interproximal elbow technique.||Figure 10. Football-shaped diamond creating lingual reduction of 2 mm or greater for FRC framework.|
|Figure 11. Final preparation shows round line angles without sharp corners.|
The patient wore the spring aligner for 6 weeks (Figure 8). During that time, interproximal slendering allowed the anterior teeth to align. Occlusal equilibration was then performed to remove posterior interferences and establish cuspid rise and anterior disclusion. Ideally, this case could have now been restored with porcelain lamination of the lower anteriors, but the fundamentals of the disclusion were satisfied. The patient was referred to the periodontist with Kodachromes and computer imaging for soft tissue ridge augmentation. During the periodontal procedures, the bonded bridge was removed and the pontic modified in order to accommodate the new ridge thickness.
Veneer preparations were made. The anterior teeth were prepared using a 0.7-mm depth-cutting diamond bur. The interproximal elbow and incisal wrap technique of 1 to 1.5 mm was performed. A chamfer finish line was prepared at the crest of the gingiva, allowing 2 mm of porcelain interproximally (Figure 9). The lingual surfaces of teeth Nos. 7 and 9 were prepared with a bullet-shaped diamond. An accentuated chamfer of 1 to 1.5 mm is needed at the gingival margin. To allow for the necessary thickness of the FRC framework material, a minimum thickness of 1.5 mm of lingual reduction is recommended with a football diamond bur (Figure 10). All aspects of the final preparation require rounded line angles without sharp corners8 (Figure 11). An ovate pontic site was prepared in the augmented ridge with an Ellman Radiosurgical Unit (Ellman Manufacturing Co) set on the fully rectified wave.
All preparations were sealed with number 1 OptiBond primer (Kerr Corp), a dentin bonding agent. Final impressions were taken with Extrude (Kerr Corp). Centric occlusal bite records and Chromascope Shades (Ivoclar Vivadent) were taken. Provisional restorations were now fabricated with Temphase (Kerr Corp) (Figure 12). A releasing agent was applied to the prepared teeth followed by syringing the Temphase composite provisional material lightly on both the preparations and the previously prepared stint. A one-piece provisional was trimmed, then luted to the teeth with OptiBond number 2 resin (Kerr Corp) without any etching.
The patient feedback on the provisional was ascertained after 3 to 5 days. Lengthening anterior teeth requires a period of adjustment of the patient’s orofacial musculature. Premature adjustments such as shortening and thinning incisal edges occur if this period of acclamation is not respected. A model of the adjusted provisionals was sent to the lab technician.
The final restorations were fabricated according to previously described techniques.9 The restorations were returned and inspected for proper fit, contour, and color.
|Figure 12. Maxillary provisionals in place.||Figure 13. Split dam technique.|
|Figure 14. Cementation of the FRC framework. Attention should be made to eliminate any flash that would prevent seating of the veneers. Nexus dual-cure cement (Kerr Corp) sets to a gel state, which facilitates easy removal.||Figure 15. Seated IPS Empress veneers.|
The provisionals were removed with a hand composite trimmer (CLV-7, Hu-Friedy), and the restorations tried in by seating the FRC framework first, followed by the pressed ceramics. After patient approval, the teeth were anesthetized and then isolated with a split dam technique (Figure 13).
The preparations were cleaned with a pumice wet with chlorhexidine, then rinsed. All surfaces were conditioned with 37% phosphoric acid for 10 to 15 seconds, then rinsed and left slightly moist. The preparations were disinfected with a glutaraldehyde preparation (Gluma, Heraeus Kulzer). The abutment preparations were then sealed with four to five coats of OptiBond F1 primer (Kerr Corp) followed by OptiBond dual-cured resin 3A and 3B. The FRC framework was then cemented with dual-cured Nexus Cement (Kerr Corp), being careful to remove all flash, which would prevent the seating of the veneers (Figure 14). The pressed ceramic veneers were then cemented with the rapid placement technique (Figure 15). All veneers were seated at one time, followed by spot curing in the middle third with the Optilux 500 (Kerr Corp) curing light with the 2-mm curing tip, then cleanup and final curing. Occlusal adjustments were then made.
Final contouring was performed with fine diamonds, 30 fluted carbides, high-speed rubber cups, and diamond polishing paste. Incisal edge nuances were created with diamond discs. These slight irregularities, which align with the labial anatomic folds, break up light transmission and impart realism to the final result (Figures 16 through 19).
|Figure 16. Pretreatment anterior dentition.||Figure 17. Posttreatment anterior dentition.|
|Figure 18. Occlusal view of aesthetic and functional lingual contours.||Figure 19. Completed maxillary restoration.|
This article describes a practical sequence to aesthetically restoring the worn anterior dentition while fulfilling the principles of sound occlusal function. The use of leucite-reinforced pressed ceramics conservatively reestablished anterior form and function. Although long-term recorded data with Ceromer/FRC materials has yet to be reported, the data and experiences to date are promising.
The sequence of restoring mandibular anterior, maxillary anterior, mandibular posterior, then maxillary posterior allows for systematic rehabilitation of occlusion while satisfying the aesthetic desires of most patients to “do the front teeth first.”
Restoring the worn dentition to beauty and function is a challenge that can be met today with greater ease then ever before. It is truly an exciting time to be a restorative dentist. The marriage of aesthetic materials with adhesive technology facilitates this, yet pretreatment planning and communication is the key to success!
Author’s Note: A complimentary copy of the smile design checklist can be obtained by contacting Dr. Rosenberg.
1. Williamson EH, Lunquist DO. Anterior guidance: its effect on electromyographic activity of the temporalis and masseter muscles. J Prosthet Dent. 1983;6:816-823.
2. Schyler CH. Fundamental principles in the correction of occlusal disharmony, natural and artificial. J Am Dent. 1935;22:1193 -1202.
3. LD Pankey Institute. The Rule of Thirds. Continuum II, Diagnosis & Treatment Planning. 1991
4. Tauati B. Defining form and position. Practical Perio Aesthet Dent. 1998;7:800-807.
5. Rosenberg J. The use of computer imaging to enhance treatment planning and case acceptance. Contemp Esthet Restor Pract. March/April, 1998.
6. Fuzzi M, Bonfiglioli R. Utilization of leucite glass ceramic veneers for complex case rehabilitation. Pract Perio Aesth Dent. 1998;5:605-609.
7. Fahl N, Casselinni R. Ceromer FORD/FRC technology: the future of biofunctional adhesive aesthetic dentistry. Signature. 1997;1:7-13.
8. Zanghelli Nig. Fiber-reinforced framework and ceromer TM restorations: a technical review. Signature. 1997; 1:1-5.
9. Chandler R. Unique features of the IPS Empress System. 1996 Laboratory Digest. Mahwah, NJ: Montage Media.
Dr. Rosenberg maintains a private practice in Philadelphia, Pa emphasizing restorative and aesthetic dentistry. He is a fellow of the Academy of General Dentistry and holds associations with various restorative, aesthetic, and orthodontic organizations. He publishes in this field to increase awareness of high-tech materials and procedures and performing dentistry more efficiently and with higher quality. Dr. Rosenberg places hundreds of bonded restorations monthly and has a patent pending in the area of nonmetal dental restorations. He is also the head of The Dental Healthcare Group, which provides high-quality continuing education in the Philadelphia area. He can be reached at (215) 592-4747.
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