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Gold or porcelain-fused-to-metal (PFM) crowns traditionally have been considered the “go to” choice when strength and long-term function are needed from a restoration that can be fabricated predictably and easily.
Gold or porcelain-fused-to-metal (PFM) crowns traditionally have been considered the “go to” choice when strength and long-term function are needed from a restoration that can be fabricated predictably and easily. However, an innovative PFM one build powder (InLine One, Ivoclar Vivadent) was recently introduced to enable laboratory ceramists to enhance their productivity when fabricating crowns and bridges. The InLine One ceramic is based on a leucite-forming ceramic glass. Based on their homogenous structure, the leucite crystals contained in the glass matrix demonstrate a small grain size. As a result, laboratory technicians can benefit from the material’s workability, strength and luminosity when creating restorations that are gentle to opposing dentition.
Refer to slideshow for figures.
The patient presented with a fractured lower second molar that required endodontic treatment (i.e., root canal) and a crown (Fig. A). A PFM restoration featuring a new one-layer ceramic (In-Line One) in Vita Shade A1 was indicated.
01 Two sets of quadrant models (e.g., white and blue) were used to fabricate the single crown restoration. The white set was the “clean design” model (i.e., except for exposing the margin, no adjustments were made), which ensured the true, proper fit of the restoration design and a pleasing final presentation. This clean set was used to check contacts and occlusion without being hinged together; articulating the models by hand through their occlusal excursions provides an unrestricted perspective (Fig. B). The blue set, which serve as the “dirty working” models, are hinged together to facilitate waxing, building, adjusting and tapping in the occlusion.
02 From start to finish, it is important to follow the proper techniques-from metal design to porcelain layering. Starting with a full wax-up that can be referenced using both sets of models is the best approach for creating a baseline throughout the case (Figs. C, D and E). All clearance and anatomical design should be worked out in the wax-up, ensuring that it coincides with the substructure and layering ceramics. Any preparation reductions or opposing adjustments should be made during the wax-up stage, allowing sufficient time to ask the prescribing doctor for permission.
03 A snap putty mold was made and used as a reference guide for waxing the pattern design of the metal substructure (Fig. F). For optimal light reflection, refraction and laminating strength, the selected ceramic material (InLine One) requires a minimum thickness of 0.8 mm and a maximum thickness of 2 mm (Fig. G). Therefore, it was necessary to ensure the substructure design followed the cusp fossa relationship that was built into the occlusion (Fig. H). The wax-up design also served to control the harmonious gradient of color throughout the entire restoration from the inside out, so the wax margin was cut back for a small porcelain margin.
04 Using a lost wax technique, the wax pattern was invested and cast. A high noble metal, white gold based dental alloy (Sagittarius, Ivoclar Vivadent) was used. The casting was fitted, requiring only minor adjustments, and was cleaned by blasting with alumina oxide. It then was run through a degassing cycle in preparation for porcelain application (Fig. I).
05 The oxidized metal substructure was opaqued with shade A1 by first applying a wash layer (Fig. J), then fired a second time at 930°C with a full-coverage opaque layer to block out any metal color. In this case, a porcelain margin was required, which was applied in two separate firings. Because the InLine One materials are fully compatible with all powders from the conventional InLine product line, standard margin materials can be used. Because the margin materials and opaquers can be fired at the same temperature, the thin areas of opaque could be touched up at the same time (Fig. K).
06 Once the margin was complete, the remainder of the crown was built using the Dentcisal 1 powder, after which the restoration was fired at 910° C (Fig. L). The restoration demonstrated some shrinkage after the first build and required a second build with more Dentcisal 1 powder, after which it was fired at 900° F (Fig. M). This decision was based on a comparison of the build-up to the wax-up to ensure the proper shape and occlusal cusp to fossa relationships had been established. Internal characterization stains can be used to modify the shade prior to the second build, but they were not required for this case.
07 The final anatomy was scribed in using a highspeed 701 carbide fissure bur. A clear glaze was then applied to the entire restoration (Fig. N). Although it wasn’t required for this case, external characterization stains can be used to enhance the shade.
When fabricating these types of crowns, the shade is controlled mostly by the color of the selected opaque. InLine One Layering Dentcisal powders allow the opaque to shine through the layers, producing a harmonious shade from the inside out (Fig. O). For opaque layers to exhibit magnificent reflections, the substructure must complement the final design. If the restoration requires more fluorescence, opaque F can be applied prior to the Dentcisal build-up.
The InLine One system is easy-to-use and enables technicians to focus on the shape of their crown restorations. It also is ideal for technicians looking to advance from gold crown waxing to porcelain building. Additionally, the system shows great promise for easing first-time bridge builders into less complicated layering techniques. Because the InLine One system delivers uncompromised esthetics, it represents an ideal alternative for technicians who prefer to hand layer their crowns, rather than press to metal.
About the author
Andrea L. Hegedus, CDT, BS, owns Great Lakes Smile Design Studio in Muskegon, Mich. Building a career in dentistry over the last 25 years, she completed a Bachelor of Science with Honors in Prosthodontics from Ferris State University in 1990, is an active member of the American Academy of Cosmetic Dentistry, Francis B. Vedder Study Club, NADL, and MACDL and has completed numerous courses with PAC-Live at the University of Pacific Dental School and with The Hornbrook Group at the University of Texas, Houston Dental Branch. She also has studied under ceramic masters, Matt Roberts, Marv Staggs, Oliver Brix, Michel and Inge Magne, and leading dentists, Drs. Mark Montgomery and Ron Ritsco. Contact her at Andrea@glsmiledesignstudio.com.