Long-term Reliabilty of Zirconia-based Fixed Partial Dentures

Material and Methods: Between 2003 and 2009 a total of 121 patients with 236 restorations (200 single crowns and 36 bridges with a maximum span length of 21 mm, altogether 322 units) were included in this study. All teeth were prepared with an equi- or subgingival chamfer preparation (r = 2.25 mm). The cores of the crowns and bridges were produced using the computerized CERCON technique (DeguDent, Germany) and did not differ in design and thickness. The mean thickness of core plus veneering layer (CERCON Ceram Kiss, DeguDent, Germany) was 2.5 ± 0.5 mm. The crowns were luted onto vital abutments using ZnO-P-cement (Harvard, Hoffman&Richter, Germany) or composite cement (BiFix, Voco, Germany) in case of non vital teeth. Occurring failures (chipping, fracture, marginal gaps, etc.) were determined at half year check-ups and documented. FPDs with major failures were excluded from further recalls. The type of crown failure was analyzed in detail by clinical examination. Data was evaluated statistically using the survival analysis after Kaplan-Meier (Logrank- Test p=0.0005).

Results: The mean observation period of the whole sample was 31±6 months. CERCON all-ceramic system demonstrated natural and esthetical appearance. Three framework fractures were recorded, 12 chippings and 5 de-attachments were seen mainly during the initial wearing period (0-4 months). After an observation period of 71 months, the overall failure was 10,2 % including 5,8 % for chipping defects.

Conclusions: Zirconia demonstrated sufficient stability as framework material for crowns and brigdes. The analysis of chipping defects suggested occlusal and technology causes.