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RESTORATIVE CHALLENGE: A middle-aged male patient presented with a failing three-unit PFM bridge on teeth #6-8 (see Figure 1).
Restorative team: Brian Lindke, CDT, Beautiful Smiles by VIVIDX, Inc., and Tim Resuta, DDS, both of Atlanta, Georgia
Treatment plan: Preliminary study casts were made and sent to the laboratory. The casts were mounted, then evaluated to determine treatment options. The team decided to replace the existing bridge with a CZR PRESS bridge. At the laboratory's request, Dr. Resuta also prescribed a pressable veneer on tooth #9 to ensure a more predictable, esthetic outcome.
Noritake CZR PRESS was chosen because of its many indications. It can be pressed over zirconium frames, and simultaneously pressed as a veneer, using the same ingot, within the same pressing ring. The team determined that the bridge framework would be fabricated from 3M ESPE's Lava zirconium-oxide material. The framework ends at the bottom of the axial wall in preparation for a 360° pressed margin (see Figure 2). Pressing directly to the zirconium-oxide framework assures the best marginal fit and increases light transmission into the tooth and gingiva.
Case study: Dr. Resuta removed the existing PFM bridge and prepared #9 for a pressable veneer.
Brian Lindke sent the master model and opposing model to Lab Solutions in Atlanta for fabrication of the Lava framework. Upon receipt at Vividx, Lindke thoroughly inspected the frame for form, including pontic placement/size, connector placement/size, material thickness and color. He used Noritake Crack Finder, a liquid ink, to ensure there were no cracks.
The framework was selectively modified to assure optimum thickness of the press material, and sandblasted with 50µ aluminum-oxide at 30 psi to produce a surface more conducive to accepting the bond layer of ceramic.
Lindke applied Shade Base Stain--a micro-particle-sized, colored, translu-cent ceramic--to the frame to ensure ultimate wetting of the ceramic to the zirconium oxide and increased bond strength (see Figure 3). Because Shade Base Stain is colored and translucent, he used it to further boost chroma and control value at the framework level. He then weighed the zirconium framework; this weight would be needed later to determine how many ingots to use when pressing.
The zirconium oxide frame was placed on the working model and the margins were meticulously waxed around the framework to establish the final marginal fit. Next, wax was added over the framework to establish a definitive dentinal form. The veneer on #9 was also waxed to final dentinal form (see Figure 4). When the waxup was complete, sprues were added, and the bridge and veneer were weighed together. Finally, Lindke subtracted the framework weight from the total wax weight to determine the net weight/number of ingots for pressing.
The bridge and veneer were invested in the same ring with Noritake CZR PRESS Investment. Lindke selected a CZR PRESS LA1 (low translucency) ingot. After pressing and divesting, the restorations were cut-off and seated onto the master model; no internal adjustment was required.
To replicate the patient's natural tooth characterizations, Lindke used the Internal Live Stain technique; CZR Internal Stains were painted directly onto the pressed dentin and evaluated for placement and intensity. The stains were set by quick-firing at a low temperature with no hold time.
Enamel and Luster (opalescent) powders were used to finalize the anatomical contours of both the bridge and veneer (see Figure 5). Only one bake was required for the bridge and veneer because the dentinal form consisted of press ceramic, which facilitated a minimal enamel thickness and consequently afforded little shrinkage. The contacts were adjusted and the restorations were contoured, texturized, glazed and mechanically polished to the desired luster.
At the cementation appointment, Dr. Resuta, Lindke and the patient carefully evaluated the restorations for fit, form and function. The team determined that the case was both clinically and esthetically acceptable and restorations were seated (see Figure 6).
Contact information: Darby Dental Laboratory Supply, Co., Inc.; 800-826-6050 (New York); 800-828-3393 (Denver); 800-247-2385 (Kansas City); 800-423-1877 (Reno); 800-354-5227 (Atlanta); or click here to visit the website.
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