Creative Artistry for Crown-and-Bridge Provisional Restorations
The essence of the crown-and-bridge provisionalization goes far beyond traditional “temporary” methodology. A well-constructed provisional restoration affords the dentist and the patient the opportunity to preview the direction and ultimate success of the laboratory-processed restorations. When esthetic and functional requirements are worked out in the provisional restoration, restorative predictability is greatly enhanced. Morphologic design, anterior guidance, cuspid disclusion, occlusal plane, curve of Spee, curve of Wilson, occlusal-vertical dimension, and anterior esthetic arrangement are but a few critical details that can first be worked out in the best articulator in the world—the one between the patient’s ears. Once the “patient-generated” functional requirements are satisfied, a stone model of the completed provisional restoration provides the laboratory technician with a visual prescriptive of the definitive restoration. Using a preoperative impression of the existing malocclusion with broken-down occlusal surfaces as a template for the provisional restoration provides the dentist and technician with absolutely no useful information. Also, without precise margination and emergence profiles, the periodontal sulcular environment can quickly turn into a mushy quagmire of edematous, bloody tissue to be dealt with at final impressions and delivery of the case. The purpose of this article is to give the dentist some artistic insight into creating provisional restorations that act as “progenitor restorations” in the methodical treatment of esthetic and functional dental rehabilitation.
Master the Morphology
According to Dr. Harold M. Shavell, the definition of a dental restoration is “the utopian reintegration of lost morphotypia via biomorphomimickry.” In other words, dedication to the replication of natural tooth contours is paramount to long-term restorative and esthetic success. The provisional restoration is the first step toward achieving that goal. In the posterior region, the occlusal surfaces are made up of a series of elevations (cusps) and depressions (fossae), that allow opposing elements to interdigitate in what is termed “maximum intercuspation.” Dr. Shavell taught that understanding the proper morphology of the mandibular first molar was key to understanding the occlusion. The mesiolingual and distobuccal cusps touch in the central fossa; the mesiobuccal and distolingual cusps do not. Cuspal elements are parabolic and free flowing in form and are not static or linear by design.1,2
Provisional Crown-and-Bridge Materials
There are three materials commonly used to fabricate provisional restorations—methyl methacrylate (acrylic), bis-acrylics, and composite resins. Methyl methacrylates have a lower elastic modulus and are, therefore, less brittle than the other two materials. For that reason, they are indicated for bridge spans of more than one pontic, because they will be less likely to fracture in the edentulous area. Bis-acrylics are good materials for single units and one-pontic bridges because they are easy to dispense, and can be modified if necessary with flowable light-cured composite. Direct composite resin can be used as a provisional material for individual labial veneers or multiple veneers as long as the preparation is only spot-etched and primer is not used to bond the provisional material to place. Laboratory-processed provisional restorations are excellent choices for cases that require long-term provisionalization (several months) because the fabrication process makes the material, whether acrylic or composite, more dense and, therefore, stronger than when fabricated using traditional chairside techniques.
Functions of the Provisional Restoration
The provisional restoration serves three very important functions. First, it provides an interim seal for the prepared tooth. Good marginal integrity and proper emergence profiles provide the framework for healthy maturation and maintenance of the periodontal environment. This is particularly important when the definitive restorations are to be bonded in place. The success of the delivery procedure depends on the operator’s ability to control the sulcular environment during the bonding process. Second, the provisional restoration provides an “esthetic preview” for the patient. During this time, esthetic and functional parameters—such as “the golden proportion,” width-to-length ratios, canine disclusion, and anterior guidance—can be worked out to the patient’s and dentist’s satisfaction. And third, occlusal schemes can be evaluated and tested during function, including restoration of occlusal vertical dimension, providing essential diagnostic information for the laboratory technician to use when creating the definitive restorations.3
Artistically Created Provisional Restorations:Methodology and Armamentarium
In the clinical environment, an artistically contoured and well-marginated provisional restoration nurtures the periodontium and stomatognathic mechanism during the interim phase of treatment. Preparations are made to conserve the maximum amount of tooth structure for designing structurally sound and esthetic tooth-colored restorations. Bis-acrylic provisional crown and bridge materials are commonly used to fabricate many types of transitional (provisional) restorations for inlays, onlays, and single and multiple full-coverage units.
Case Presentation 1
A patient presented with tooth No. 19 missing from a previous extraction. The second and third molars had drifted forward, resulting in a space too small to place a molar pontic(Figure 1). A composite mock-up was done on a preoperative study cast to design the appropriate pontic for the remaining space(Figure 2). It was decided that a premolar tooth could be placed in an esthetic and functional position. Had the space been smaller, rather than place a pontic that was too small from a mesiodistal dimension, it would have been appropriate to overcontour the distal of the second premolar and the mesial of the second molar and close the space without a pontic.
A provisional matrix was fabricated from the preoperative composite mock-up using a clear plastic stent material and a thermoplastic suck-down device. After the teeth were properly reduced, the provisional material was dispensed into a matrix and placed on the prepared teeth for approximately 2 minutes(Figure 3 and Figure 4). Once the provisional shell was recovered from the matrix(Figure 5), a sharp lead pencil was used to delineate margins and the contact zones proximally, so they would not be accidentally damaged during the carving process. Multiple single-unit provisional restorations are usually splinted for ease of handling and durability during function. Specially selected instrumentation was used to artistically carve the morphologic tooth replicas. A safe-sided diamond (D911HD-220, Axis Dental, Coppell, TX) was used to make the initial cut between units as the gingival embrasures were developed (the patient must be able to use floss threaders to maintain the interproximal tissue health while in provisional restorations). A round-end tapered, laboratory acrylic carbide bur (UCO79E-040, Axis Dental) was then used to remove marginal excess up to the pencil line, then to develop proper emergence angles in the cervical third of the restoration. Three-quarter?inch fine garnet sandpaper discs can be used to help create facial and lingual contours in three planes (cervical, middle, and occlusal). After using a sharp lead pencil to draw the parabolic cusp forms in their proper orientations on the occlusal surfaces of the acrylic(Figure 6), a tapered fissure bur (H23-010HP, Axis Dental) was used to release the occlusal morphology(Figure 7). The bur was angled at 45° and used to “draw” over the pencil lines. Next, a small diamond disc (0943-080, Axis Dental) was used to delineate separation between units, developing facial and lingual embrasure form. An impregnated composite polishing brush or medium-grade pumice on a chamois wheel was then used to polish the finished restoration. A final luster was achieved using a small, dry muslin wheel. A centric occlusion bite registration was taken using a stiff vinyl polysiloxane (VPS) bite registration material (Registrado X-tra, VOCO America, Inc, Sunnyside, NY)(Figure 8). The registration was taken on the prepared side only so that the patient’s true centric occlusion could be visually verified in the anterior and right posterior regions(Figure 9). A master impression of the prepared area was made using a VPS impression material(Figure 10). The completed morphologic provisional restoration for the mandibular three-unit segment, shown in Figure 11, Figure 12, and Figure 13 can be compared to the completed ceramic reconstruction in Figure 144,5.
Case Presentation 2
For cases where the existing teeth are in the proper arch position and have good anatomic contour remaining, it is possible to use a VPS registration material as a matrix for the provisional restoration. A standard “triple tray” can be used for this matrix only if there are solid occlusal stops on the teeth anterior and posterior to the operative area(Figure 15). Another alternative matrix to consider would be a putty stent made from a preoperative study model. A good preoperative model should reproduce enough of the alveolar process and surrounding hard tissue landmarks to provide an accurately positioned positive seat for the matrix when occlusal stops are not present. In this case, teeth Nos. 29 and 30 were prepared for all-ceramic, full-coverage restorations(Figure 16 and Figure 17). Defective amalgams have been removed along with associated decay and the preparations were built up using glass ionomer cement as a dentin replacement. After retraction of the gingival tissues with retraction cord, a master impression of teeth Nos. 29 and 30 was made using a VPS impression material. To create a translucent effect in the occlusal one third of the provisional restoration, a translucent bis-acrylic provisional material (StructurPremium QM, VOCO America, Inc) was syringed into the cuspal areas of teeth Nos. 29 and 30 of the provisional stent(Figure 18 and Figure 19). The base shade provisional material—in this case, B1 (StructurPremium, VOCO America, Inc)—was then syringed on top of the translucent material already in place, filling the remaining space in the matrix(Figure 20). The provisional stent was then placed on the preparations and the patient closed into maximum intercuspation while the provisional material set. The same protocol as described in Case Presentation 1 was used to carve the provisional restorations to correct anatomic contour and marginal precision. The provisional restorations, shown in Figure 21 and Figure 22, were cemented in place with a eugenol-free temporary cement material (Provicol QM, VOCO America, Inc). Occlusion was checked with articulating paper and adjusted and polished as needed(Figure 23).
Conclusion
A quality provisional restoration is essential for consistent excellence in esthetic and cosmetic restorative dentistry. Expectation levels of today’s dental patients are at an all-time high because of media exposure and education by the dental profession regarding new materials and techniques. Beautiful provisional restorations help the dentist to understand what the patient is looking for esthetically, to restore proper function and physiologic contours, and to help communicate the desired result to the laboratory technician via study models and digital photography. For cosmetic patients, provisional esthetics provides “immediate gratification” and can be a real practice builder. We have all had patients who present with esthetic and functional “nightmares” only to want immediate results. Without properly designed provisional restorations, the dentist is “working in the dark,” only to expect that the laboratory result will be perfect and acceptable to the patient. An exquisite provisional restoration takes the pressure off the dentist and actually becomes an “artist’s canvas” to which acrylic, composite, and colorants can be added or subtracted at will until the desired result is achieved. The laboratory technician then has a 3-dimensional prescription for fabrication of the definitive restoration. With the proper shade information, he or she can then create a predictable restoration that will satisfy the esthetic and functional requirements of the patient.6
References
1. Shavell HM. Mastering the art of provisionalization. Calif Dent J. 1979;7(5):42-49.
2. Shavell HM. Mastering the art of tissue management during provisionalization and biologic final impressions. Int J Perio Rest Dent. 1988;8(3):25-43.
3. Lowe RA. The art and science of provisionalization. Int J Perio Rest Dent. 1987;3:64-73.
4. Lowe RA. Predictable fixed prosthodontics: technique is the key to success. Compend Contin Educ Dent. 2002;23(2 Suppl 1):4-12.
5. Lowe RA. Tips for successful provisional restorations—every time for every case. Dental Products Report. 2002;36(10): 68-72.
6. Lowe RA. Provisionalization: mastering the morphology. Dental Products Report. 2003; 37(8):56-58.
About the Author
Robert A. Lowe, DDS
Diplomate
American Board of Aesthetic Dentistry
Private Practice
Charlotte Center for Cosmetic Dentistry
Charlotte, North Carolina
