Objective : The purpose of this study was to compare the effect of the high intensity halogen light (85 01000 mW/cm´-) with that of the conventional halogen light (400 mW/cm2) on the hardness of composite resin.
Materials and Methods : Three resin composites (Z-100, 3M, USA; Tetric Ceram, Vivadent, Liechtenstein; SureFil; Dentsply, USA) were filled in the stainless steel moulds which were 3mm in diameter and 2, 3, 4, and 5 mm in depth, respectively. They were cured under the four differei,t modes : (1) conventional mode, 40 seconds at 400 mW/cm2; (2) `ramp´ mode, 10 seconds at 100 to 1000 mW/cm2 plus 10 seconds at 1000 mW/cm2; (3) `boost´ mode, 10 seconds at 1000 mW/cmZ; and (4)
`standard´ mode, 20 seconds at 850 mW/cm2. The surface hardnesses of the top and the bottom of the resin samples were measured with a microhardness tester (MXT70, Matsuzawa, Japan).
Results : The top surface hardness was not significantly different among the curing modes. The bottom surface hardness was generally the highest in the conventional mode and the lowest in the high intensity boost mode. There was no significant difference in the bottom surface hardness between the conventional mode and the high intensity standard mode in 2mm depth.
Conclusion : The results suggest that the curing time of the high intensity halogen light (8501000 mW/cm) should be at least 20 seconds to produce the equal level of hardness of resin composite as compared to the hardness produced by the conventional halogen light (400 mW/cm2).
|