Degree of conversion and cross-link density of resin composites formulated with different photoinitiators

Abstract

This study verified the influence of light curing units (LCU) in the degree of conversion (DC) and cross-link density (CLD) in composites formulated with different photoinitiators. LCUs XL2500™ (3M/ESPE), Apollo95E ™ (DMD), UltraBlue IS™ (DMC) and Ultra- Lume5™ (Ultradent) were used, all them in agreement with the manufacturers’ recommendations and with 19J of radiant exposure. Pyramid-Bisco™ (photoinitiator Lucirin TPO) and FiltekZ250™-3M/ESPE (photoinitiator camphorquinone) were used. DC was measured by infra-red spectroscopy. CLD was measured indirectly with Knoop hardness before and after immersion in ethanol. Data were submitted to ANOVA and the averages to the Tukey test (5%). LCU Apollo95E™ produced the largest values of DC for the composite TPO (60.2%) when the radiant exposure was maintained constant. LCU UltraBlueIS™ was not capable of photoactivating the composite TPO. There were no differences in the values of DC to the composite CQ, unless when Apollo95E ™ was used by the manufacturer’s time, producing the lowest average (50.8%) of DC. In general, Ultra- Lume5™ produced greater CLD, while Apollo95E™ the smallest CLD for composite TPO. For the composite CQ there was no pattern for the values of DLC. Therefore, it is concluded that, photoinitiator systems affect properties of light-curing resin composites.