Microhardness of composite resins: effect of photocuring units and polymerization periods in different depths

Abstract

The properties of composite resins have been frequently studied, as well as the factors that might influence the polymerization degree. Considering the evolution of composites and the need to improve their clinical performance, this study intends to evaluate the efficacy of two high-intensity and one low-intensity photocuring units, as a function of exposure time (20 and 40seconds) and composite depth (from 1 to 4 millimeters). Composite properties were evaluated via Knoop Microhardness Test. Statistical analysis (1 way ANOVA, p < 0.05) of the obtained results showed that there was statistically significant difference regarding the time factor. The 40-seconds polymerization time showed the best results, for the four depths. Concerning the photocuring unit factor, there was statistically significant (1- way ANOVA, p < 0.05) difference between the tested devices. The high-intensity units demonstrated better results than the low-intensity one. There were statistically significant differences between the analysed composite depths, being the highest microhardness values achieved for the lowest depths.