Curing method for reducing polymerization contraction stress of light-curing resin composite

光固化树脂复合材料具有美观、使用方便、与牙齿结构结合良好、力学性能提高等优点，目前已广泛应用于临床。然而，光固化树脂复合材料通常是从靠近光源的树脂表面聚合的，这会导致树脂复合材料对光的聚合收缩。与自固化树脂复合材料相比，这种收缩在树脂和腔壁/地板之间产生了更多的间隙。本项目旨在评估不同c因子形状树脂复合修复体的光旋法对边缘密封和腔壁适应性的影响，以及增量填充技术对树脂与I类牙本质-腔地板微粘结强度的影响。采用双光固化法对树脂-牙界面进行了环境扫描电镜观察。结果表明，增量充填技术并不能提高牙本质与牙槽底的微结合强度。另一方面，采用慢启动固化方法；270 mW/cm^2 10 s + 5 s（间隔）+ 600 mW/cm^2 50 s可降低聚合收缩应力，并倾向于提高边际密封性和树脂复合材料对腔壁的适应性。普通固化法；600 mW/cm^2 60 s导致边缘密封性和壁面适应性差。环境扫描电镜观察表明，慢启动固化方法提高了树脂复合材料对牙腔壁的适应性，对有牙釉质缘和无牙釉质缘的牙腔均有效。

Light-cured resin composites are now widely used in daily clinical practice because of their esthetic advantages, ease of use, good bonding to tooth structure, and improved mechanical properties. However, light-cured resin composites are usually polymerized from the resin surface near a light source, which causes polymerization contraction of the resin composite towards the light. This shrinkage creates more gaps between the resin and cavity wall/floor than self-cured resin composites.This projects was to evaluate the effect of the light wring method on the marginal sealing and cavity wall adaptation on resin composite restorations with different C-factor shapes and also to evaluate the effect of incremental filling technique on resin micro-bond strength to Class I dentin-cavity floors. Moreover, environmental SEM observation was carried out to evaluate on resin-tooth interface using two light curing method.It was concluded that incremental filling technique did not improve dentin micro-bond strength to cavity floor. On the other hand, slow-start curing method ; 270 mW/cm^2 10 s + 5 s (interval) + 600 mW/cm^2 50 s reduce the polymerization contraction stress, and tended to improve marginal sealing and resin composite adaptation to the cavity wall regardless of bonding system and C-factor. Ordinary curing method ; 600 mW/cm^2 60 s resulted in poor marginal sealing and wall adaptation. Environmental SEM observation showed that the slow-start curing method improved resin composite adaptation to the cavity wall and this curing method was effective to the cavities both with and without enamel margin.