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

光固化树脂复合材料因其美观、使用方便、与牙体结构结合良好、力学性能得到改善等优点而广泛应用于临床。然而，光固化树脂复合物通常从靠近光源的树脂表面聚合，这导致树脂复合物朝向光的聚合收缩。本研究旨在评价轻挤方法对不同C因子形状的树脂复合材料牙体边缘封闭性和洞壁适应性的影响，以及增量充填技术对I类牙本质-洞底树脂微粘结强度的影响。并对两种光固化方法的树脂-牙体界面进行环境扫描电镜观察，结果表明：增量充填技术并不能提高牙本质与洞底的微粘结强度。另一方面，慢启动固化方法; 270 mW/cm^2 10 s + 5 s（间隔）+ 600 mW/cm^2 50 s降低了聚合收缩应力，并且倾向于改善边缘密封和树脂复合材料对腔壁的适应性，而与粘结系统和C因子无关。常规固化方法; 600 mW/cm^2 60 s导致边缘密封性和壁适应性较差。环境扫描电镜观察表明，慢启动固化法提高了树脂复合材料与洞壁的密合度，对有釉质缘和无釉质缘的洞均有效。

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.