The aim of this study is to determine the effects of size and type of filler particles on marginal and internal adaptation of restorations filled with different experimental resin composites in order to establish formulations with more favorable characteristics for the dental application. For this purpose, experimental composites based on BisGMA / TEGDMA with different sizes and types of fillers (barium glass and feldspar, in different sizes and combinations - 10 experimental composites) will be prepared using a high speed mixer. Gap formation will be assessed by SEM analysis. A hundred bovine incisors will be selected and ground to expose a flat enamel area, where a conical cavity was prepared. The teeth will be distributed into ten groups (n = 10), according to the type and size of the filler particle of the experimental composite. In all preparations, restorative procedure was standardized: the adhesive system Single Bond 2 will be applied according to the manufacturer's instructions and experimental composite will be placed a single increment and photocured for 40s. After 24h, specimens will be polished using SofLex system and a replica of each restoration will be obtained in epoxy resin for evaluation of superficial margins. To evaluate the internal adaptation, specimens will be sectioned and replicas of the longitudinal section will be obtained. All replicas will be observed by SEM, in 20 to 200X magnification in order to determine the percentage of gaps along the superficial margins of cavity and bonding interface. Additionally, morphological characterization of the filler particles will be performed in SEM. Data will be submitted to normality test, if normal distribution were observed, data will be submitted to ANOVA and Tukey's test (alpha = 0.05). If there is no normal distribution, the data will be submitted to the nonparametric Kruskal-Wallis test, considering a significance level of 5%.
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