| 1880 Progress on Glassy Joins for Laminar Dental All-Ceramic Restorations | ||
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M. SAIED1, Y. WANG2, I.K. LLOYD2, O.C. WILSON, Jr.3, M. ROSENBLUM4, and V. THOMPSON5, 1University of Maryland College Park, Washington, DC, USA, 2University of Maryland, College Park, USA, 3The Catholic University of America, Washington, DC, USA, 4University of Medicine & Dentistry of New Jersey, Paramus, USA, 5New York University, USA Objectives: Our goal is to develop a glass for joining individually-optimized solid-freeform fabricated veneer and core layers in dental restorations. Currently, thermal expansion (CTE)-matched porcelain veneers are applied to ceramic (alumina or zirconia) cores by labor-intensive layering. Joining individually-fabricated computer-aided design and manufacturing layers may allow optimized properties of each layer in a crown while reducing manufacture time. The join layer needs to form a strong, CTE-matched bond with a firing temperature low enough not to affect veneer geometry. Methods: Design-of-experiments methods integrating Schott factors -indicators of CTE- were used to modify the composition of a sol-gel derived alkali-silicate-borate glass precursor. The precursor was melted and quenched to homogenize it and remove residual organics. Barium and sodium content were varied to adjust join glass melting temperature (Tm) and CTE. Initial characterization included determination of Tm and CTE match/degree-of-crazing via optical microscopy. CTE, join strength and toughness of the most promising compositions were determined by dilatometry, ultrasonic modulus and micro- and nanohardness testing. Commercial Schott technical and sealing glasses were used as benchmarks. Results: Increasing barium content improves chemical resistance, promotes sintering, and lowers viscosity, while increasing sodium raises CTE, lowers Tm, and reduces chemical resistance. CTE-mismatch results in cracks (crazing) in the glass layer, while high joining temperatures affects low-Tm veneers, hence optimum quantities of barium and sodium are essential. Preliminary join studies indicate that CTE match is critical and that the glass wets and bonds to both alumina core and porcelain veneer layers. Studies are on-going with respect to interaction between composition, CTE, Tm, bond strength and toughness. Conclusions: Using a thin glass layer to join individually-optimized and manufactured layers in a laminar crown is feasible. Control of CTE, Tm and wetting behavior of the join glass is critical. Supported by NIDCR PO1DE10976. | ||
| Seq #214 - Ceramic Crowns, Core, Zirconia, Stress, Fracture 2:00 PM-3:00 PM, Saturday, 11 March 2006 Dolphin Hotel Pacific Hall | ||
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