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The aim of this study was to evaluate the thermocycling effect on of laboratory composite resins. 30 disks were fabricated,5 mm of diameter and 2mm of width, using 3 laboratory resins: G1 (n=10)- RESILAB MASTER (Wilcos-Brasil), G2 (n=10) - Vita VMLC (VITA-Germany), and G3 (n=10) - Vita Zeta (VITA-Germany). Vickers microhardness (HV) of all specimens was using a microhardness tester FM-700 (Future Tech- 50 g/10s). specimens were measured before and after the thermocycling (3.000 and 12.000 times - 5° /55°C±1). The microhardness before cycling were (mean±SD): G1: 55.50±4.6; G2:35.54±2.5; G3: 27.97±1.6.; after 3.000 thermocycles: G1:55.54±3,9; G2: 29.92±2,73; G3:21.01±1.4 and after 12.000 G1:54.27±3.2; G2: 30.91±1.6. G3: 23.81±0.9. analysis (ANOVA) and Tukey's test was accomplished(p<0,05), the highest microhardness values were observed in G1; G2 G3 showed reduction of microhardness values. It was concluded that, thermocycling, the tested laboratory composites resins are to the decrease of surface microhardness.
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Pereira et al. (2008) studied this question.