Comparative Depth of Cure Among Two Light-Cured Core Build-Up Composites By Surface Vickers Hardness

OBJECTIVE: Depth of cure of composite material is restricted and it depends on many parameters such as thickness. The aim of this in-vitro study was to evaluate the depth of cure of two light-cured core build-up composites (Quixfil and Photocore) in different thicknesses, when cured for 60 seconds. MATERIALS AND METHODS: The Vickers microhardness measurements were made for each side of the top irradiated surfaces of 1,2,3,4,5,6,7 and 8-mm-thick cylindrical blocks of two core build-up light-cured composites (Quixfil and Photocore) and a micro hybrid composite (Z250) as the control group. For each thickness a bottom to top Vickers Hardness Number (VHN) ratio was determined and a value of at least 80% was used to indicate the acceptable depth of curing. The results were analyzed with two way ANOVA and Tukey HSD test. P value<0.05 was considered significant. RESULTS: A two way ANOVA indicated that both the depth of cure and VHN were significantly influenced by composite type (P< 0.001) and thickness (P< 0.001). The bottom to top VHN ratio reflecting the relative curing degree showed acceptable curing at a depth of 5 mm for Quixfil and Photocore; however, it was 3 mm for Z250. The surface micro hardness of Photocore was significantly higher than the other materials in all thicknesses. CONCLUSION: Although both two composites can be bulk cured, their curing depths were lower than that was expected. Curing depth is a property which is material specific and decreases with thickness (P < 0.001).