November 1, 2005
by D. Dwayne Karateew DDS and Marco Beschizza MDT
To successfully complete a rehabilitative aesthetic treatment, a team composed of the treating dentist, a dental ceramist, necessary specialists and the patient must be formed. The success or failure of the treatment depends on the knowledge and skills of the treating dentist, who must be the intraoral architect of the treatment and must fully understand the potential contributions of each team member. A careful treatment plan must also be developed. The plan should contain the correct steps placed in a logical sequence and communicate the necessary information to each member. Allowing them to idealize his or her individual contribution to achieve the best possible result for the patient.
DIAGNOSIS AND TREATMENT PLANNING
After developing a sequence for treatment, the treating dentist should send information to the laboratory before the fabrication of a diagnostic wax-up (Fig. 1). An impression and photographs of the resin mock-up are necessary. It is imperative that the photographs include the patients pre-treatment smile (Fig. 2). This is to facilitate the ceramists requirements to visualize the teeth to be restored within the clinical context, namely framed by the borders which the lips provide. This series of photographs should be taken of the preoperative condition as well as the mock-up. Impressions of both arches should be taken utilizing the same techniques as one would use for the final restorations. A bite relation in maximal intercuspation (CO) can be taken in a rigid registration material or a terminal hinge axis bite is utilized if there is to be a modification of the functional occlusal surfaces. A stick bite parallel to the horizon and a full-face photo of the patient with the stick in place serves as a leveling device in the laboratory, however, it is always preferable to use a face-bow for relating the occlusal plane of the study models to the condylar element of the articulator.
RESTORATIVE PRE-TREATMENT SEQUENCE
Diagnostic waxing in the laboratory gives the dentist the opportunity to learn a great deal about the subsequent treatment. The procedure must start with modification of the stone model followed by adding wax to achieve the final desired contours and function. Establishment of the desired incisal edge position can now be established and utilizing preconceived ideals for tooth size and shape, a decision can be made whether or not to alter the gingival margin position and underlying bony architecture (Fig. 3A). As a general rule of aesthetics, the arch created by the gingival zeniths should follow the upper lip and the incisal edge of the maxillary teeth should follow the superior portion of the lower lip (Fig. 3B). A preliminary functional evaluation should be conducted at this time. Anterior disclusion, canine guidance, clearance of the non-working cusps in the posterior, and proper overbite/overjet relationships should be achievable with the planned treatment or a change in treatment need to be considered. In the continuation of this process, consideration is given to the ‘golden proportions’, ideal length to width ratios, axial inclination, contact point and incisal embrasure positioning as well as maxillary functional surface anatomy. If gingival/osseous corrective surgery is to be performed, these steps will have to be repeated, or at least modified, once new study models are obtained following complete healing of the surgical area.
PREPARATION AND PROVISIONALIZATION
The diagnostic models, photographs and mountings were used to plan a conservative treatment approach to gain aesthetic functional, and phonetic harmony. The communication protocol established between the participants will lead to a predictable plan for the preparation, provisionalization and fabrication phases of treatment. Using the diagnostic wax-up, preparations can be carefully co-ordinated with reduction guides fabricated from sectioned putty matrices. All teeth are prepared with the same sequence of burs and areas of reduction (Fig. 4). Regulation of the reduction steps in a repeated sequence is important as it bring uniformity to all preparations and allows for ideal preparations. Final records, including underlying photographs of the preparations, the final impression, face-bow, and bite registration were captured.
The goal of this systematic restorative approach was to achieve form, function, and aesthetic objectives with the provisional restorations which are derived from the diagnostic wax-up, then transfer that information to the definitive restoration without losing information. With this in mind, a hand stacked feldspathic ceramic restoration was selected. Natural contour, textural and subsurface character and ideal 3-D positioning (buccal-lingual and mesial-distal) are perhaps more critical factors than colour (hue, value and chroma), therefore there is much attention paid to these in order to achieve a SuperNatural smile (Fig. 5). After meeting all of the goals of the case in the provisional restorations, the case must be re-created in feldspathic ceramics utilizing all the artistic skills of the ceramist (Fig. 6). This is perhaps the weak-link in hand stacked restorations, whereas pressed ceramics can utilize the diagnostic wax-up directly to recreate the desired contours.
The final restorations are inspected for marginal fit and evaluated on the master dies. The patient is anesthetized, and the provisionals are carefully sectioned so that the underlying tooth structure is not damaged. The preparations are cleaned with a chlorhexidine scrub and each individual restoration is tried on the respective tooth to appraise the marginal fit. All of the restorations are tried-in with a glycerine based color matched try-in gel to evaluate the final value of the ‘cemented’ restorations and to verify the interproximal contacts. After the patient has given verbal approval each restoration is washed, dried and treated on the intaglio surface with three percent hydrofluoric acid which then is washed off and dried after the requisite time has passed. The teeth themselves are treated with 35 percent phosphoric acid which is washed off after 10 seconds on dentin and 30 seconds on enamel. The ceramic is treated with a silane wash and adhesive while the teeth themselves are coated while wet with a dentin/enamel adhesive system. The restorations are loaded with light-cured resin cement, seated, held into place, and excess cement is cleaned off. Each restoration is tacked cervically at the midface of the individual restoration. Proper cleaning of the interproximal surfaces are critical. Careful flossing of the interproximal area of the centrals ensures minimal finishing postcuring. The laterals and the cuspids are then cemented with the same technique. The restorations were light-cured for 2-3 minutes each. Final cement clean-up followed by occlusal adjustments under water spray and final polishing are then completed (Fig. 7).
The success or failure of any restorative treatment is assured in the planning phase before any tooth is touched with a bur. By carefully working through the diagnostic process then using the gathered information during preparation and transferring that information through the provisionalization and final fabrication process, all gaps that could result in guesswork are filled. By following a systematic approach the end result of treatment becomes a forgone conclusion, not an event anticipated with apprehension.
Dwayne Karateew DDS, Dip. Perio, Dip. Prostho, obtained his DDS from Columbia University in New York and Diplomas in both Periodontics and fixed Prosthodontics from the University of Pennsylvania. He participates as a member on the Faculties of the University of British Columbia, University of Washington, the University of Pennsylvania and Columbia University. He practices in Vancouver, BC.
Marco Beschizza RDT, MDT, trained and qualified as a dental technician in England. He then attained a special
Masters Diploma at the Wielemdorf Masters School in Germany in 1989 where he ran a specialized cosmetic laboratory and developed and manufactured the MOONS Ceramic System. He maintains a laboratory in Vancouver, BC.
Oral Health welcomes this original article.