Influence of a simulated oral environment on microleakage of two adhesive systems in Class II composite restorations

Objectives: The aim of this in vitro study was to evaluate the influence of a simulation of intra-oral conditions on the microleakage of two adhesive systems (Scotchbond MultiPurpose Plus=SBMP+ and Clearfil SE Bond=SE Bond). For SBMP+, the influence of bonding procedure (comparison between manufacturerʹs protocol and an experimental procedure) was also studied. Methods: Sixty Class II cavities with cervical margins 1 mm below the cemento-enamel junction were prepared in the mesial/distal surfaces of recently extracted human molars. For the 3 groups (n=10), the adhesive system was applied under ambient conditions (20 °C/40% of relative humidity (RH)) for the mesial cavity and under extreme conditions (35 °C/95% RH) for the distal cavity. SBMP+ and SE Bond were applied strictly according to manufacturerʹs instructions. SBMP+ was also used according to an experimental procedure (intensive evaporation of the primer solvent). Cavities were restored with Z 100. After polishing, the specimens were thermocycled (2000 cycles, 5–55 °C). Teeth were coated with nail varnish, immersed in silver nitrate and sectioned longitudinally. The extent of microleakage was measured in percentage of dye penetration. Statistical analysis was performed using a 2 way ANOVA and a Fischerʹs PLSD test. Results: Microleakage was dependent on the environmental conditions. In ‘35 °C/95% RH’ conditions, dye penetration significantly increased for the 3 groups. For SE Bond, the microleakage percentages were the lowest, both in ambient and extreme conditions. For SBMP+, the experimental procedure allowed a decrease in microleakage, but only in ambient conditions. Conclusions: The simulation of intra-oral conditions caused a large increase in microleakage in the 3 groups tested. The self-etching primer presented the best behavior towards the ‘temperature/RH’ parameters simulated in this study.