Effects of Different Curing Tip Distances on Surface Hardness of Composite Resins

The purpose of this study was to evaluate the surface hardness value of Silorane and different composite restorative materials upon exposure to different distances between the light source and the resin surface. Five different composite resins used in the study (Filtek Silorane, Filtek Supreme, Premise, Grandio, Inten- S). Twenty samples were prepared for each group (n=100) and the resin thickness was 2 mm. Composite groups were divided into 4 sub-groups with 5 samples each. These groups were determined according to distances [0 mm (surface contact), 3 mm, 6 mm and 9 mm] to be applied during the polymerization process between the light source tip and resin surface. The composite samples were prepared using stainless steel molds with a 5 mm diameter cavity and heights of 2 mm. The composite resins were placed as incremental, covered by transparent mylar strips at the top and bottom and compressed with finger pressure between glass slides. During the polymerization to standardize the distances between the tip of the units and the resin composite surface, rings corresponding in height to distances were used. LED light device was used in this study and samples were polymerized for 40 s. For each sample 3 indentations were made at the top and bottom surfaces and averaged to determine the hardness value. According to the 2-way-ANOVA, the restorative materials and distance between the light source and resin surface were statistically significant for the bottom and the top surface of the specimens. The lowest hardness was observed in 9 mm. The highest VHV was observed in Grandio group. When comparing the top and bottom surfaces, there were statistically significant differences in all study groups. To ensure adequate depth of cure, manufacturers’ recommended curing times should be extended whenever curing light tip distances are increased.