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ABSTRACT:The aim of this study was to evaluate the diametral tensile strength (DTS) of composite resins submitted to different curing techniques. Four composite resins were tested in this study: Targis (Ivoclar), Solidex (Shofu), Charisma (Heraeus-Kulzer) and Filtek Z250 (3M Espe). Sixty-four cylindrical specimens were prepared and divided into eight groups according to each polymerization technique (n = 8). The indirect composite resins (Targis and Solidex) were polymerized with their respective curing systems (Targis Power and EDG-lux); Charisma and Filtek Z250 were light-cured with conventional polymerization (halogen light) and additionally, with post-curing systems. Specimens were stored in artifi cial saliva at 37°C for one week. DTS tests were performed in a Universal Testing Machine (0.5 mm/min). The data were statistically analyzed by ANOVA and Duncan tests.

Objective:This study evaluated the effect of the margin location and an adhesive system on the marginal adaptation of composite restorations.Material and Methods:Class V cavities were prepared in bovine teeth with the gingival margin on the dentin and the incisal margin on the enamel. The cavities were restored with a micro-hybrid composite resin using an etch-and-rinse [Single Bond 2 (SB)] or a self-etching adhesive [Clearfil SE Bond (CL)]. After finishing and polishing the restorations, epoxy replicas were prepared. The marginal adaptation was analyzed using scanning electronic microscopy (SEM, 500 x magnification). The higher gap width in each margin was recorded (T0). After the first evaluation, the samples were submitted to thermal cycling (2,000 cycles of 5ºC±2ºC followed by 55ºC±2ºC - T1) and mechanical cycling (100,000 cycles of 50 kN and 2 Hz - T2). Replicas of samples were rebuilt after each cycling and analyzed under SEM. The data were submitted to Mann-Whitney, Wilcoxon and Friedman testing (a=0.05).Results:The SB presented higher gaps in the dentin than the enamel, while there was no difference between the substrate for the CL. In the dentin, the CL showed better marginal sealing than the SB. The opposite occurred in the enamel. There were no significant differences between the baseline, thermal and mechanical cycling for any experimental condition.Conclusions:The outcomes of the present study showed that the adhesive system and margin location have an important effect on the marginal adaptation of composite restorations.