Effect Of Alcoholic-drink, Light-unit and Exposure Time On Composites Properties

Objectives: To evaluate the performance of light-curing-units (LCUs) and exposure times on the degree of conversion (DC) of different composites; and the effect of 30 days alcoholic-drink immersion over the Knoop microhardness (KHN) and the surface roughness (Ra) of those materials. Methods: Composite discs 2mm thick were fabricated from five materials: Filtek SupremePlus A2D, Filtek SupremeXT A2E, Filtek Z250 (3M ESPE), Durafill and Venus (Heraeus Kulzer). The LCUs used were Halogen–Optilux501/Demetron and Blue LED–EliparFreeLight2/3M ESPE. The exposure times were half-, full- and double the time recommended by the manufacturers. After 24h in distilled water (37^oC), the specimens were polished and after desiccation, DC was established with ATR-FTIR. KHN and Ra were obtained before and after the wine storage. The alcoholic-drink was renewed every week (pH~3.65). Statistical analysis was performed using Repeated Measures ANOVA/ stepdown Bonferroni for non-related pairs and Bonferroni correction for related pairs (p<0.05).Results: For DC, KHN and Ra, each of the factors studied (Resin, LCU, Cure Time, Wine Exposure and Surface) was a statistically significant factor (p<0.05) either overall or in an interaction with one or more other factors. Ra of composite surfaces was not significantly affected after the wine storage, except of the bottom surface of Durafill. HKN of the top surface of specimens was significantly reduced after the wine storage, except for Venus and Durafill. KHN of the top surface was higher than the bottom surface, and significant difference was found between the DC of the surfaces. Conclusions: HAL and LED did not significantly differ from one another in their general performance. Significant differences were found for specific composite materials and exposure times. In general, the light exposure for double of the recommended time did not improve the performance of the composites compared to the time recommended by the manufacturer.