Factors associated with microleakage in Class II resin composite restorations

This in vitro study investigated the correlation between factors related to cavosurface marginal adaptation and microleakage in Class II cavities restored with a light- or chemical-activated resin composite. Standardized cavities were prepared in 40 molars that were randomly divided between both materials. Each of the groups was, in turn, divided, so that the restorations were placed by incremental and bulk techniques. The resultant four groups (n = 10), each with material/technique variations, had their marginal gaps measured by environmental scanning electron microscopy at randomly selected facial and lingual points of the proximal box of each restoration. After sectioning the teeth, interfacial dye penetration was assessed by light stereomicroscopy according to an ordinal scale at the same locations as for the marginal gaps. In a general linear model with microleakage as a dependent variable, no correlation between marginal gap size and microleakage was found (p = 0.802), although the interaction of the material and placement technique (p = 0.028) and material alone (p = 0.063) influenced microleakage. The model explained 63% of the variation in microleakage. It was concluded that, irrespective of the possible role of marginal gap in the occurrence of microleakage, the choice of material and placement technique are important determining factors in microleakage.