Evaluation of battery level and distance of led light curing on the microhardness of bulk fill composite resin

Objectives: to analyze the influence of the battery level and the distance from the light source have of a light-curing device on the microhardness of a bulk-fill composite resin. Material and Methods: the battery level of a Radii-Cal LED light curing device (SDI) was standardized (100% and 50%) using a radiometer. The distance from the light source to the composite resin was standardized with an acrylic matrix (0mm, 2mm, and 8mm). Thirty samples (4mm x 6mm) were made with the Filtek One Bulk Fill (3M/ESPE), divided into six groups (n = 5) based on two battery levels and the three distances from light source. They were subjected to the Vickers microhardness test, performing three superficial and three basal analyses. To perform comparisons between the groups, the F-test (ANOVA) and Tukey's multiple comparison was used with 5% of error margin. Results: The microhardness averages decreased when the light-curing distance was increased for each battery charge level. When analyzing the reduction in battery charge, it was found that some groups had significantly higher averages when photopolymerized at 100% charge. Conclusions: In view of the limitations of the present study, these results can negatively influence the clinical performance of bulk fill composites resins.