Nanohybrid versus nanofill composite in class I cavities: margin analysis after 12 months.

This study evaluates the margin of a nanofill, a nanohybrid, and a conventional microhybrid composite in restorations in occlusal cavities of posterior teeth after 12 months. Forty-one patients, each with three molars affected by primary caries or the need to replace restorations, participated in this research. The teeth were restored with a nanofill (Filtek Z350), a nanohybrid (Esthet-X), and a microhybrid as a control (Filtek Z250). Ten patients were selected randomly, and the three restorations were molded with a low-viscosity polyvinyl siloxane material. The molds were poured with epoxy resin, gold-sputter coated, observed by scanning electron microscopy, and classified as: "perfect margin," "marginal irregularity," "marginal gap," "marginal fracture," or "artifact." For statistical analysis, the Wilcoxon and Friedman nonparametric tests and paired-samples t-test were used (significance level of 5%). The performance of the three materials was compared after 1 week and 12 months. No statistically significant differences were detected for all criteria (P > 0.05). When each composite was compared over time, statistically significant differences were found for the criterion, perfect margins (Esthet-X and Filtek Z350, P < 0.05). The materials performed satisfactorily over the 12-month-observation period, but all composites under investigation showed a certain amount of deterioration relating to marginal quality over time.