Effect of Light Curing Distance of Different Bulkfill Composites on Top to Bottom Microhardness

Abstract

Dental composite restorations have a major drawback regarding the degree of cure, which is proportional to the amount of light they are exposed to. So, they polymerize to a certain depth which varies with the penetration of a light beam in the bulk material. The present investigation was done to evaluate top to bottom microhardness of different bulk-fill composites at different light curing distances and different curing times. Three bulkfill materials Admirafusion xtra (voco), Tetric Evoceram bulkfill (Ivoclar vivadent) and Filtek bulkfill (3M.) were used. The top and bottom surfaces of the three bulkfill composite specimens were irradiated at two different distances 0mm and 4mm. Sixty composite speciemens were prepared in cylindrical Teflon molds (4mm×4mm) diameter that are open at the top and the bottom sides and cured according to manufacturer's instructions and 40seconds by using elipar S-10 light curing unit. The different light curing distances were standardized by means of a holder coupled to the light cure controlled by an electronic digital caliper. After curing process, the speciemens were stored at 37˚C at 100% humidity for 24 hours, surface microhardness were measured and Data presented as means, standard deviations(SD). Microhardness showed a parametric distribution, Multivariant ANOVA used to study the effect of different Curing time, curing distance and materials on top and bottom values of Microhardness followed by post-hoc test for pairwise comparison when ANOVA is significant with Bonferroni correction. One way ANOVA used to study the effect of different curing time, curing distance and materials on top/bottom ratio of microhardness. Results showed that curing time, curing distance and materials showed a statistically significant effect on top and bottom values of microhardness at p ≤ 0.05.