Inside Dental Technology
May 2011, Volume 2, Issue 5
Published by AEGIS Communications
A Sign of the Times
Advances in clinical digital photography enable technicians to apply proven "old school" concepts in new ways.
Looking at the repertoire of today's dental technicians, it is apparent that many still employ a number of "old school" concepts and techniques—approaches they have learned and continue to use, sometimes without taking the time to question whether they are relevant to current fabrication processes.
Some of these methods are not that old in terms of years, but are still considered "old school" because they have come to be considered indispensable for optimal case outcome. Others are regarded as foundational elements of dental technology's best practices, and still others are merely progressions of previous techniques.
Technicians must educate themselves about the latest developments, examine what techniques in their toolboxes make sense, and decipher whether the concepts they have used in the past are still relevant. For example, let's take a look at two accepted standards in the industry—the metal try-in and the bisque-bake try-in— examining the rationale behind each and their potential outcomes.
Old School: Metal Try-In
The metal try-in is a concept still taught in many prosthodontic programs today. Dental students are taught that when treating and fabricating large restorative cases, they should ask that individual metal substructures be tried in and picked up in an impression. The individual metal substructures are then soldered together, re-tried in, and re-impressioned. The object of the exercise is to avoid issues with passivity and marginal fit. The next step in the process is the bisque-bake try-in to evaluate tooth position, color, and the esthetics of the case. The last steps include a possible re-try-in and then the final glaze and finish process.
To be clear, verification of the fabrication steps in a case is valuable and sometimes necessary. However, the approach to verification should be systematic and of true benefit to the procedure. Today, the concept of a metal try-in is somewhat outdated. Based on the author's experience, splinting large frameworks together has become a thing of the past, with the practice of implant placement. The complicated frameworks once required to bridge large edentulous areas have now been simplified by implant placement.
And even though very accurate castings that fit the die and solid cast can be fabricated; the "old school" process is still not a perfect science. The steroidal creams often used during the insertion procedure helped to move tooth position to the frame rather than the other way around. Adding to the challenges of the metal try-in concept, most cases today are prescribed with 360° ceramic margins, which makes frame try-ins more difficult.
For ceramists, the most troublesome struggle in a large case is the "old school" concept of a porcelain try-in for final result. Without the proper diagnostic work and a blueprint of final case outcome, the porcelain try-in is nothing more than an estimated guess. The ceramic effects, midline, emergence profile, and incisal position incorporated into the ceramic build-up for esthetic results are for naught if gross adjustment to any of these areas is needed after the chairside try-in. To make any one of these adjustments would require reducing the ceramic work almost back to the beginning.
The purpose of the porcelain try-in today should be reserved for final, last-minute esthetic tweaks that do not influence the foundational ceramic work involved in the build-up process. The translucencies, effects, and color graduations incorporated in the build-up allow the restoration to blend into the oral environment (Figure 1 and Figure 2). A guideline of the incisal edge and midline must always be considered in the case-planning stage. The key is to have the restoration follow the blueprint of the wax-up and provisionals and then execute the try-in, using photography to communicate slight improvements in the esthetic outcome.
New School: Bisque-Bake Try-in
To achieve the optimal esthetic result, each step of the process should demonstrate continuing improvements, starting with the patient's preoperative situation (Figure 3). The wax-up and provisionals lay out the diagnostic blueprint (Figure 4 and Figure 5). At this point, the provisionals should be adjusted chairside to address any necessary esthetic changes and then photographed. The photographs are sent to the technician for evaluating the case plan and for making any slight changes that are needed to the final restorations. The value of photography is critical to the final esthetic results (Figure 6 and Figure 7). The ceramic build-up can now follow what is seen in the patient's face and allows slight improvements to be made (Figure 8), with the technician able to focus on color since the basic shape has already been provided. The bisque try-in is photographed and allows the technician to make any small, last-minute adjustments to improve the final result (Figure 9).
When evaluating the photograph of the bisque try-in, it is possible to see how close the restorations are to the desired final result. The clinician marked the incisal edges of teeth Nos. 8 and 9 to suggest a slight 0.5-mm reduction, thus creating a more natural-looking incisal edge specific to the patient (Figure 10). This bisque evaluation provides an esthetic roadmap for making only slight changes.
In Figure 10, it is clear that the height of contour on teeth Nos. 8 and 9 is an area of concern. Although they are somewhat acceptable, improvements could be made to enhance the final look. Marking the line angles in red pencil or in gold dust confirms what the bisque shows in Figure 11 and Figure 12. Also the emergence profile seems to be a slight issue. Using a small amount of additive ceramic, the technician can address both issues (Figure 13, Figure 14 and Figure 15). After firing, a few minutes are spent creating a more natural emergence profile. Again, the pencil marks play an important role in the evaluation (Figure 16 and Figure 17).
Often the biggest challenge technicians face is in the ability to control esthetic cases. Although it may seem as if taking these extra steps could decrease the profit margin in such cases, they are worth the time investment because otherwise, the technician stands to lose the patient and client's confidence if the case has to be returned for major adjustment (Figure 19, Figure 20 and Figure 21). Applying extra knowledge and effort into case preparation not only protects the field of dental technology but also is an investment in its future.
About the Author
Peter Pizzi, MDT, CDT, FNGS
Owner and Manager
Pizzi Dental Studio Inc.
Staten Island, New York