완속기시(Soft-start) 광조사 방식이 복합레진의 중합 및 수축응력에 미치는 효과

Abstract

The purpose of this study was to evaluate the influence of soft-start light curing on contraction stress and hardness of composite resin. Composite resin in acrylic mold (inner diameter 7mm, outer diameter 10mm, height 2mm) was cured using the one step continuous curing method with three different light sources; conventional halogen light curing for 40 seconds at 400 mw/㎠, plasma arc light curing for 6 seconds at 1300 mW/㎠ and LED light curing for 10 seconds at 700 mW/㎠. And the soft-start curing modes with two different light sources; plasma light curing for 2 seconds light exposure at 650 mW/㎠ followed by 3 seconds at 1300 mW/㎠ and LED light curing with exponential increase for 5 seconds followed by 10 seconds at 700 mW/㎠ were used. Contraction stress was measured using strain gauge method and also Vickers hardness was measured 24 hours after polymerization at the top and bottom of specimens. Resin-acrylic interfaces were observed using a scanning electron microscope(SEM). The results of present study can be summarized as follows: 1. Composite resin in acrylic molds showed the initial expansion at the early phase of polymerization. 2.Contraction stresses at 10 min after polymerization were significantly reduced with the soft-start curing both in plasma and LED light sources(P<0.05). 3.Plasma light curing with soft-start resulted in not only the lowest contraction stress, but also the lowest hardness (P<0.05). 4. LED light curing with soft-start showed lower contraction stress than the one-step continuous halogen and LED light curing (P<0.05). 5.Microhardness of specimens cured by LED light with soft-start was equivalent to that of cured by the one-step continuous halogen and LED light (P>0.05). 6.Curing by LED light with soft-start and conventional halogen light resulted in better marginal sealing than plasma light and one-step LED light curing. On the basis above results, we think that LED light curing with soft-start provided the reduction of polymerization contraction stress, the adequate hardness of surfaces and the proper marginal sealing.