RESUMEN
The aim of this study was to evaluate the extent of microleakage in class V cavities prepared with bur, Er: YAG laser and ultrasonic, hybridized with two different bonding agents ["Single bonding", a solvent-free bonding agent, and "Swiss TEC SL bond", an alcohol-based solvent]. Thirty freshly extracted human premolars were divided into three groups of ten teeth each according to the device used in cavity preparation: Group 1] Er:YAG laser [500 mJ, 10 Hz, 63.69J/cm 2]; group 2] ultrasonic device and group 3] diamond burs. On each tooth, two cavities were prepared, one on the buccal surface and one on the lingual surface. Each group was subdivided into two subgroups of 5 teeth each according to the bonding system used: subgroup a] "Single bonding" and subgroup b] "Swiss TEC SL bond]. Cavities were restored with a micro-hybrid composite resin. After thermocycling, the specimens were immersed in 2% methylene blue solution for four hours and then sectioned in the buccolingual direction. Dye penetration was scored using a stereomicroscope. The two-way ANOVA test and paired t-test revealed no statistically significant differences among the methods of preparation [conventional, laser and ultrasonic]. However, statistical differences were found between the adhesive tested; the "Single bonding" had lower microleakage values than "Swiss TEC SL bond". Based on the results of this study it can be concluded that the Er: YAG laser and ultrasonic device are as effective as the conventional method in preparing cavities. The extent of microleakage depends on the type of the bonding agents