Abstract
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≤0.05) and LSD’s 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.
Highlights
Composite resin is the most widely used restorative material in dentistry
Analysis of one-way ANOVA followed by LSD test showed no significant difference statistically between the control group and all the experimental groups (p=0.64)
A low temperatures can increase the viscosity of the composite resin which will slows the movement of monomer molecules to polymerize
Summary
Composite resin is the most widely used restorative material in dentistry. The advantages of composite resins in mimicking the original tooth color is the reason of its frequently used. The success of composite resin restoration obtained from its aesthetic value and durability of use over a long period of time. Some of the parameters that may affect the polymerization of composite resins are composition, color and translucency, light curing unit characteristics, irradiation distance, exposure time and temperature. Temperature may affect the polymerization of the composite resin, which affects the properties of the composite resin and its quality. An adequate polymerization of composite resin will increase the degree of conversion that influence the properties of composite resin, such as strength, hardness, water sorption and solubility [1]
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