Effect of simulated gastric acid on the surface degradation of dental ceramics.

Abstract

Objective: The aim of this study was to compare the effect in vitro of simulated gastric acid solution on the roughness, microhardness and micro-structural topography surface of two dental ceramics: lithium disilicate glass-ceramic and monolithic zirconium dioxide (ZrO₂) at baseline and after different immersion time.

Materials and methods: Lithium disilicate and ZrO₂glass-ceramic discs were fabricated (40 of each one) and was evaluated under microscope the roughness (Atomic force microscopy), microhardness (Vickers hardness tester) and micro-structural topography surface (Scanning electron microscopy) before immersion (baseline) and after three periods of immersion: 8 h 25 min, 46 h 2.5 min and 92 h 5 min in simulated gastric acid solution of hydrochloric acid (HCl, 0.06 M, pH 1.2) at 37 ºC. The ceramics were compared over time with a repeated measures analysis of variance (ANOVA).

Results: Statistically significant changes (P<.05) were found in the microhardness values between both ceramics, which decreased after all times points of immersion in simulated gastric acid solution, ZrO₂showed higher microhardness mean values (P<.05) but lithium disilicate showed significant changes (P <.05) in the surface microhardness at baseline versus the three immersion times. Lithium disilicate had higher roughness values than ZrO₂(P<.05), which increased after 8 h 25 min of immersion; however, after 46 h 2.5 min and 92 h 5 min of immersion, the roughness decreased. More microporosities were observed in the lithium disilicate surface than with ZrO₂.

Conclusion: The simulated gastric acid solution of HCl affected the roughness, microhardness and micro-structural topography surface of both lithium disilicate and ZrO₂, but greater surface degradation was presented lithium disilicate.