ABSTRACT
AIM: The aim of this study was to evaluate two composite restorations (conventional methacrylate-based and low shrinkage-based silorane), associated or not to beveling and incremental technique, in relation to the microleakage and marginal gap formation tests. MATERIAL AND METHODS: 30 sound human molars had their mesial and distal surfaces prepared with and without bevel. The teeth were divided into six groups according to the type of resin (conventional nanofilled or silorane resin), and restorative filling technique (incremental technique or builk). Microleakage and marginal gap formation data were statistically analyzed by Kruskal-Wallis and Chi-Square tests, with a significance level set at 5%. RESULTS: Group 1 (Z350 XT, without bevel, incremental technique) presented highest rate of microleakage and marginal gap in most of the restorations, with statistically significant differences. Groups 4 and 6 (P90, beveled, builk and P90, beveled and incremental technique) had lower rates of microleakage and absence of marginal gaps in most of the restorations. CONCLUSION: It's concluded that the silorane showed lower rates of marginal gaps and microleakage, when compared to the conventional methacrylate-based resin. Bevel preparation was effective in reducing microleakage and marginal gaps for both resins used. Incremental technique was not necessary when associated with low shrinkage composite resin.