Surface hardness of dental composite photopolymerized with different light sources and polymerization time

Abstract

Purpose: The aim of this in vitro study was evaluate the microhardness in dental composites photo activated in a distance of 8mm, what simulates the first composite increment in a restoration class II. Thereunto, 45 specimens were confectioned using a nanopaticulate composite (Filtek Z350 – 3M Espe. The specimens were divided randomly in 9 groups (n=5). Each group differed in the photoactivation mode used (1600 mW/cm² Bluephase 16i (BLP); 800 mW/cm² Ultralume 5 (ULT); 500 mW/cm² XL3000 (XL)) and in the temperature of composite in the moment of polymerization (23°C, 54°C or 60°C). After the preparation of specimens, they were submitted to the microhardness Knoop test (KHN) on the surfaces and bottom, and the results were charted and submitted to the statistical analysis. There were no significant statistical differences in relation to the photoactivation modes used for all the surfaces and temperatures tested. For ULT, there was no significant statistical hardness in relation to the temperature of the composite. For XL and BLP modes, the increase in the temperature (56?C and 60?C) provided a hardness rise in the composite on both surfaces; for XL the temperature 56?C did not differ from the control (23?C); for BLP the temperature 60?C did not differ from the control. For all the situations tested, the top surface presented greater hardness than the bottom.