Electric Current as an Alternative Method for Surface Treatment of Acid-Sensitive Ceramics

Objectives: The aim of this study was to evaluate the silane application with electric current as an alternative method for surface treatment of acid-sensitive ceramic. Materials and Methods: IPS E.max Press ceramic discs applied with silane, associated or not with hydrofluoric acid, electric current and storage time in water were divided in the groups (n=10) AE+CF (Acid etching + electric current free); AE+CA (Acid etching + electric current); AF+CF (Acid etching free + electric current free); AF+CA (Acid free + electric current); AE+CF +T (Acid etching + electric current free + thermal cycling); AE+CA+T (Acid etching + electric current + thermal cycling); AF+CF+T (Acid free + electric current free + thermal cycling) and AF+CA-T (Acid etching free + electric current + thermal cycling. In the conditioned groups, 10% hydrofluoric acid was applied for 20s. The silane was applied with microbrush in the AE+CF-T, AE+CA-T, AF+CF-T and AE+CA-T groups and in the other groups it was replaced by a metal tip conductor of electric current. Cylindrical silicone matrices with three holes (12 mm in diameter and 1mm thick) were placed on the ceramic. The resin cement RelyX U200 was inserted into the holes of the matrix, subjected to a static load of 250mg for 2min and photoactivated for 20s. After removing the matrix, the sample with resin cement cylinder adhered to the ceramic was stored in an oven at 37 ºC for 24h. The 24-h samples and those thermocycled with 10,000 cycles in vats with water at temperatures of 5±1 ºC and 55±1 ºC were submitted to microshear resistance test, fracture analysis, SEM analysis and contact angle. Data were submitted to one-way ANOVA and Tukey’s test (α=0.05). Results: At 24h, AE+CA showed the highest value in bond resistance and AF+CF at the lowest, both different from AE+CF while AF+CA was intermediate. After thermocycling, with higher values AE+CA+T and AE+CF-T were similar, as well as AF+CF+T and AF+CA+T with lower values. AE+CF+T and AE+CA+T differed statistically from AF+CF+T and AF+CA+T. Adhesive failure was predominant in all groups with or without thermocycling. At 24h, there was cohesive failures in mixed resin cement in the AE+CA and AF+CF. After thermocycling, there were mixed failures in the AE+CA+T and cohesive failures in resin cement for the AE+CF+T and AF+CA+T. The greater contact angle vas observed in the AE+CF. Conclusions: The association of hydrofluoric acid etching, application of silane with electric current and storage times promoted different values of bond strength, types of failures and contact angles in samples of resin cement bonded to acid-sensitive ceramics. Clinical Relevance: The application of silane with an electric current is a promising method to improve the adhesive bond between resin cement and ceramics, especially when associated with hydrofluoric acid etching.