Effect of Bench Time on Surface Hardness of Nanofiller Composite Resin

The purpose of this study was to evaluate the effect of different bench time on surface hardness of the composite resin after being stored in the refrigerator at 4？？C. Before used in this study, the composite resin was refrigerated at 4？？C for the test group and kept at 25？？C for the control group. The specimens were divided into control group (I) and five experimental groups according to the bench time before polymerization, 0 (II); 15 (III); 30 (IV); 45(V); and 60 (VI) minutes. Sixty specimens with 10 mm diameter and 2 mm thickness were made by using nanofiller composite resin. The material was filled into stainless steel mold and curing for 20 s. After kept in a dark box for 24 hours, the surface hardness of all specimens were tested using Microhardness Tester. The data were analyzed with one-way ANOVA (p？ü0.05) and LSD？ˉs post hoct test. The results showed that the 60 minute bench time group presented the highest surface hardness value followed by 45, 30, 15 and 0 minutes bench time group. Moreover, the hardness value of 60 min group was almost similar with the control group. Statistical analysis showed no significant differences (p>0.05) between groups. It concluded, bench time has an effect on the surface hardness of composite resin but no significant differences statistically