Clinical performance of scientifically designed, hot isostatic-pressed (HIP'd) zirconia cores in a bilayered all-ceramic system.

PURPOSE: The success of bilayered all-ceramic restorations is dependent upon the combination and contributions of the three principal components of these restorations: core material, core design, and core-veneer interface. The purpose of this paper is to describe the fabrication and clinical survival of optimized ceramic restorations having an explicit, scientifically designed core, machined from HIP'd isotropic zirconia and veneered using a specific protocol with thermally compatible porcelain. MATERIALS AND METHODS: Using a consistent clinical and laboratory protocol in a multicenter setting, 3,192 bilayered single and 797 bilayered splinted units were fabricated and placed on teeth and implant abutments in 1,007 patients. Approximately 61.7% (n = 2,462) were posterior restorations and 38.3% (n = 1,527) were anterior. Of the total, approximately 5.7% (n = 227) were placed on implant abutments. Survival of the restorations was determined with the Kaplan-Meier (KM) method by tooth number. RESULTS: For the 3,989 units placed, 9 failures were recorded. The KM survival of most zirconia restorations, when segregated by tooth number, was 100%. Exceptions were the 9 failed units, with a KM survival between 88% and 99% for those restorations. Six restorations failed within the first year of service, including three failed cores. Examination of those restorations revealed failure was related to initial design, quality assessment, or fabrication inconsistencies. CONCLUSION: The incorporation of a reinforcing ring beam onto an anatomically shaped core made from end-state HIP'd zirconia, in partnership with a thermally compatible veneering porcelain and a specific application protocol, resulted in extremely high survival rates for both anterior and posterior all-ceramic restorations after medium-term clinical use. These results equal or surpass the equivalent-term success rates of porcelain-fused-to-metal restorations.

A ten-unit all-ceramic anterior fixed partial denture using Y-TZP zirconia.

High-strength, all-ceramic systems are being recommended with increasing frequency for both anterior and posterior restorations. There are some significant differences in the physical and mechanical properties of these materials that ultimately affect their clinical performances. Consequently, these differences should be clearly understood before the restorative team selects the use of a particular system. This article reviews these differences and demonstrates the use of Y-TZP zirconia for the fabrication of a 10-unit anterior fixed partial denture.