EFFECT OF DENTAL COMPOSITE TYPE ON THE OPTIMUM IRRADIATION TIME AND DEPTH OF CURE

For many years, application of the composite restoration with a thickness less than 2 mm for achieving the minimum polymerization contraction and stress has been accepted as a principle. But a group of resin based composites (RBC) called Bulk Fill is introduced in recent years whose producers claim the possibility of achieving a good restoration in bulks with depths of 4 or even 5 millimeters. Accordingly, in this study the performance of two groups of resin based dental composites including Tetric N Ceram Bulk Fill and similar Universal type are investigated. The composite samples were prepared in Teflon moulds with a diameter of 5 mm and height of 2, 4 and 6 mm. The irradiation time for half of the samples in each depth, was 20 seconds and other specimens were cured at an intensity of 1000 mW/cm2 from the upper side of the mould for 40 seconds by an LED light curing instrument. After 24 hours of storage in distilled water, the micro hardness of the top and bottom of the samples was measured using a Future Tech Vickers Hardness testing machine. Data were analyzed statistically using the three-way ANOVA and Tukey test methods. The DC of Tetric N Ceram Bulk Fill in defined irradiation time and bulk depth, was significantly more than the universal type. Also, the DC of both composites studied was significantly reduced by increasing the bulk depths. Generally results show that the DC of the investigated bulk fill composite was better than the universal type in all the irradiation times and bulk depths. The studied universal and bulk fill RBCs had an appropriate DC at the 2 and 4 mm bulk depths respectively and using the recommended curing time of 40s can led to the slightly better value of DC in both composites.

Keywords:

dental composites , mechanical hardness , irradiation time , depth of cure , Tetric N Ceram