An evaluation of wear when enamel is opposed by various ceramic materials and gold

Statement of problem: Ceramic restorations have been known to cause wear of opposing enamel. Purpose: The purpose of this study was to evaluate enamel wear caused by 3 ceramic substrates in the glazed and polished conditions. Material and methods: Sixty ceramic discs (10 × 2 mm)-20 each of Finesse, All-Ceram, and IPS-Empress-were prepared and glazed. Each group of 20 was divided into 2 groups of 10. The surfaces of one group were ground and polished using a porcelain polishing kit (Dialite). The remaining 10 were left as glazed. Ten specimens of a type III gold alloy were cast into rectangular shapes of 10 × 12 × 2 mm and polished. Seventy human cusps were prepared from sound, caries-free, extracted teeth and abraded against the substrates in a wear machine for a total of 10,000 cycles. The cusp height loss was traced before and after the wear test using a profile projector. Mean surface roughness (R _a) values for the substrates were also recorded with a profilometer before testing. Differences in R _a were evaluated using 1- and 2-way ANOVA and the Scheffe post hoc test (α=.05). Results: One-way ANOVA indicated that enamel height loss was significantly different by material (P<.001) and surface condition (glazed and polished or glazed; P<.05). Gold, polished Finesse, and polished All-Ceram were the least abrasive, whereas glazed IPS-Empress was the most abrasive. There was no significant interaction effect between substrate type and surface condition. Significant differences were found when R _a of the substrate condition was compared with enamel wear (P<.01). Conclusions: Gold, polished Finesse, and polished All-Ceram caused the least enamel wear, whereas IPS-Empress caused the most wear. Cast gold was significantly different than glazed IPS-Empress (P<.05), whereas other groups overlapped. There was significant correlation between R _a and enamel wear (P<.01).