Simulated oral environment and microleakage of Class II resin-based composite and sandwich restorations

To evaluate the influence of the simulation of intra-oral conditions on the interfacial microleakage of Class II composite restorations.

40 Class II cavities were prepared on freshly extracted human third molars and filled with a direct resin composite technique (SBMP+ + Z100) or open sandwich technique (Fuji II LC + SBMP+ + Z100). Extreme intra-oral conditions were simulated (35 degrees C/95% of relative humidity) and compared with ambient conditions (20 degrees C/40% RH). After thermocycling (2,000 cycles--5 and 55 degrees C), 2 hours immersion in silver nitrate aqueous solution and embedding into epoxy resin, samples were longitudinally sectioned. The extent of microleakage was expressed as a percentage of silver penetration of enamel and dentin interfaces. The influences of environmental conditions and restorative technique were evaluated by a two-way ANOVA and the comparison between the different groups with a Fisher PLSD test.

In comparison with values obtained in ambient conditions, the simulation of extreme environmental conditions resulted in increased silver penetration percentages for direct resin composite restorations. On the contrary, the open sandwich technique, using resin-modified glass-ionomer cements, did not seem sensitive to excessive "temperature/relative humidity" parameters. Restorations made with resin-modified glass-ionomer cements used in the open sandwich technique appear to be more tolerant towards "temperature/relative humidity" parameters, which simulated intra-oral conditions, compared with modern adhesive systems.