55 - Dental Ceramic Surface Properties after Resin-Cement Removal by Burning Technique

Abstract

There are situations in which resin-cement needs to be removed from the crown's intaglio surface before it can be recemented. Some authors have proposed to burn off this cement; however, questions remain related to the effect of this technique on the surface properties of the ceramics. The goal was to test the effect of burning cements off on the surface properties of zirconia and lithium disilicate dental ceramics. The mechanical properties (hardness and elastic modulus) and removal effectiveness were tested in this study. Two kinds of ceramics: zirconia (Cercon, Dentsply Sirona) and lithium disilicate glass-ceramics (Emax, Ivoclar Vivadent) and two universal resin-cements; Calibra Universal (Dentsply) and Multilink Automix (Ivoclar Vivadent), were used in this research. Samples (n=8) were 1.3 mm thick and were sintered according to manufacturer recommendations. Zirconia samples were sandblasted with 150 aluminum oxide, and lithium-disilicate were etched with 9.6% hydrofluoric acid and then thoroughly rinsed. The application of each resin-cement followed the manufacturer's recommendations, and the samples were light-cured for 20 s. After 15 days of storage (100% humidity and 36 C), the samples were placed into a furnace at a temperature of ~150 C then heated a rate of ~30 C/min until reaching a temperature of 400 C where the temperature was held for 1 minute. The samples were removed from the furnace and allowed to cool before the cement was removed. Fourier Transformed Infra-Red (FTIR) was used, before and after cementation, to check the surface chemical composition and the effectiveness of the resin-cement removal. A nanoindenter (Hysitron TI 750 Ubi Triboindenter) using a Berkovich tip (100 mN) was used to assess the surface properties. Statistical analyses of the results were performed using two-way ANOVA and a post hoc Tukey test (α = 0.05). FTIR showed that the burning technique was effective to remove the residual resin-cement from the ceramic samples. Also, there was no significant statistical difference between the hardness and the elastic modulus of the dental ceramic surfaces from before and after the burning technique. This study showed that the removal of the resin-cements from crowns intaglio by the burning technique could be a viable clinical solution before recementing dental ceramics.