Comparation of Hardness of Resin Composite Samples with Three Different Curing Methods with LED Curing and QTH Equipments

The use of composite material for posterior teeth due to the esthetic demands of patients is increasing. One of the major problems of composites is the polymerization rate. Inadequate polymerization due to improper curing will result in less hardness. As a solution the best light curing system can be considered. The aim of this study was to comparate the hardness of resin composite samples with three different curing methods with LED curing and QTH equipments. In this experimental study 100 sample composite (valux plus 3M, USA) was fabricated by stainless steel mold (thickness 2mm, diameter 6mm). The teeth were divided into 4 groups of 25 (one control and 3 experimental groups). Each of the experimental group was exposed to one of the curing protocols of LED (conventional, stepped, ramped) for 20s and control group for 20 s was cured by QTH. The samples were stored at room temperature in the dark for 24 hr, then Vickers micro hardness testing was performe on the upper and lower surfaces of all samples. Significant differences were demonstrated between the different LCUs in lower and upper surfaces (P<0.05). No significant differences in the hardness between the lower and upper surfaces was found in the LED-treated groups (P>0.05). Between the two sets of LED and QTH, the role of LED curing in all modes is superiorly effective in promting more hardness.