A Modular Approach to Complex Cases
Simply dividing a problem into steps adds to precision
Due to the complexity of cases today in the dental laboratory industry, well-planned approaches are needed to ensure the accuracy and precision of the final outcomes. Often, using a modular method is helpful for working on such intricate cases. This means technicians can plan the case before work begins by dividing it into simple steps, and know which materials are needed and how they will be utilized.
To demonstrate this, the author presents a case of a lower anterior 6-unit bridge with 4 pontics. This patient had severe calculus build-ups and extremely poor hygiene, and 4 lower incisors had to be extracted (Figure 1 and Figure 2). The gingiva on the pontic sites was significantly more compromised than the gingiva on the adjacent dentition. After studying this case, it became obvious that the technician would need to replace the missing pink tissue on the pontic sites.
First, the technician created a diagnostic wax-up. It was decided that a 6-unit zirconia-veneered bridge would be fabricated with pink-gingival composite on the pontics to provide a natural seamless finish. The author planned to use Gradia® gum (GC America Inc., gcamerica.com) to best match the patient’s natural gingival color.
A model was poured using GC FUJIROCK™ EP OptiXscan and scanned (Figure 3 and Figure 4). The scan of the model stone captured all the intricate details without the use of a messy and expensive scan spray.
The CAD frame design would be completed by copying the diagnostic wax-up that had already been made. A putty stent was created from the wax-up for the dentist to create the temporary bridge. The patient wore the temporary bridge for 4 to 5 weeks with no discomfort. This made the author comfortable about duplicating the wax-up design to the substructure.
During the CAD phase, the author reduced 1 mm of the vertical incisal length and 0.5 mm from the labial to provide room for layering ceramics (Figure 5 and Figure 6). The remainder of the lingual would consist of zirconia with no veneering added. After milling, the green-state substructure was stained and sintered (Figure 7). GC Initial™ Zr-FS was used to layer the labial. Dentin B2 and CL-F, EOP3, and EOP1 were used to create white and bluish effects. FD-91 and FD-92 for the light and orange mamelons were layered by means of streaks to create complex contrasts. A thin layer of CL-F was added, and E-57 was applied to the final shape for the first bake (Figure 8 through Figure 11).
After the first firing, a small amount of porcelain was added between the connections and to highlight the surface characteristics. The key to the build-up was to not over-build in order to keep grinding at a minimum. By doing so, only a slight grinding with a fine diamond bur was needed after the bake. The ceramic was stained and glazed with GC Initial" Lustre Paste NF and fired, and ready for a try-in to take gingival shades.
Uncertain about the pink composite’s bonding ability to zirconia, the author applied a thin layer of dentin ceramic over the tissue area to ensure the bond.
Before the application of the pink composite, the gingival area of the zirconia framework was sandblasted with aluminum oxide and steam-cleaned. It then was treated with ceramic etch, and a composite primer was light cured to prepare the surface for GC Gradia gum.
There is no better shade tab for the tissue than the actual patient’s tissue, so the application of GC Gradia Gum was taken chairside (Figure 12).
GO13 was applied to opaque the zirconia. A combination of G24 and G22 was added using a cone-shaped burnisher (Figure 14). The composite was carefully applied to cover the zirconia substructure and create gingiva in the pontic areas.
After final shaping, the bridge was moved from the patient and onto the model to smooth the pontic areas and create a seamless transition. The composite then was covered with Air Barrier, cleaned, and finally glazed with Optiglaze™. This complicated case was simplified through the use of planning and a modular approach. The dentist and patient were pleased with the final outcome (Figure 15 and Figure 16).
Step ToothMaster Bay, CDT, DTG, is the founder and owner of CDI Science in Pineville, North Carolina, specializing in cosmetic dentistry and implant restorations.
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