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 manufacturer's protocol and an experimental procedure) was also studied.

Methods: Sixty Class II cavities with cervical margins 1mm 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 degrees C/40% of relative humidity (RH)) for the mesial cavity and under extreme conditions (35 degrees C/95% RH) for the distal cavity. SBMP+ and SE Bond were applied strictly according to manufacturer's 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 degrees 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 Fischer's PLSD test.

Results: Microleakage was dependent on the environmental conditions. In '35 degrees 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.