Avaliação do desacople com o tempo na resistência de união de restaurações de resina composta

Abstract

When composite restorations polymerize tensions derived from polymerization shrinkage can occur, which may lead to adhesive failures. Therefore, various methods have been proposed in an attempt to alleviate these tensions. The aim of this in vitro study was to evaluate the effect of decouple with time on the shrinkage stress of dentin- adhesive restorations in class I cavities. Ten extracted healthy human molars had standardized class I preparations (6x4x4mm± 0.01mm) and were randomly assigned to 2 groups, according to the restorative technique. Group HOR (adhesion with Single Bond Universal; horizontal technique) and group HOR5 (adhesion with Single Bond Universal; horizontal technique; decouple with time. After a 24-hour storage in water at 37°C, samples were sectioned, with a cross-sectional area of 1mm2 (0.9x0.9±0.1mm), and submitted to the microtensile test in the EMIC universal testing machine (at a speed of 0.5mm/min). Average bond strengths were analyzed using Student’s t-test. Mean bond strengths (sd) were 32.86±10.79 and 46.45±13.67 for HOR and HOR5, respectively, with significant difference (p<0.05). Decouple with time seems to enhance bond strength of resin composite class I restorations.