Department of Cariology and Endodontology, University of Geneva, Geneva, Switzerland,
Department of Cariology and Endodontology, University of Geneva, Geneva, Switzerland.
Am J Dent. 2022 Jun;35(3):123-127.
To evaluate the effect of light-curing exposure time and location on polymerization of a restorative bulk-fill resin composite to lute endocrowns.
A light-cured restorative bulk-fill resin composite (Filtek One Bulk Fill) was submitted to direct light-curing by a high-power LED light-curing unit for 20 seconds as the positive control group (n= 10). Five more groups (n= 10) were light-cured in a natural tooth mold from two sites (labial and lingual) through a nanohybrid resin composite CAD-CAM restoration (Lava Ultimate A2 LT), for different irradiation times: 90 seconds per site, 40 seconds per site, 30 seconds per site, 20 seconds per site and 10 seconds per site. Vickers microhardness measurements were made at two different depths and test/control ratios were calculated. Ratios of 0.8 were considered as an adequate level of curing. A quantile regression was run to identify the minimally sufficient time of light-curing, and a two-way ANOVA was used to compare the results to previous findings and evaluate the effect of curing location.
Analysis showed that 40 seconds x 2 is the minimal irradiation time that presents a test/control ratio above 0.8. Quantile regressions showed that the required irradiation time to reach a test/control ratio of 0.8 at a confidence level of 95% is 41.5 seconds and 39.2 seconds at 200 µm and 500 µm depths in the luting agent, respectively. There was no statistically significant difference between microhardness of the two depths except for the irradiation time of 10 seconds. The two-site to three-site light curing comparison showed no statistically significant difference except for the 90-second time.
Systematic light-curing through the labial, lingual and occlusal surfaces of thick indirect restorations is not always required for sufficient polymerization and can even waste valuable clinical time especially in the case of multiple restorations luted with resin composites.
评估光固化暴露时间和位置对 lute 内冠修复的光固化聚合效果。
采用高功率 LED 光固化机对光固化修复块状填充树脂复合材料（Filtek One Bulk Fill）进行 20 秒直接光固化，作为阳性对照组（n=10）。另外 5 组（n=10）采用纳米复合树脂 CAD-CAM 修复体（Lava Ultimate A2 LT），从唇侧和舌侧两个部位进行自然光固化，照射时间分别为每个部位 90 秒、40 秒、30 秒、20 秒和 10 秒。在两个不同深度测量维氏显微硬度值，并计算测试/对照比值。比值为 0.8 被认为是足够的固化水平。进行分位数回归以确定光固化的最小有效时间，并使用双向方差分析比较结果与之前的发现，并评估固化位置的影响。
分析表明，40 秒×2 是呈现测试/对照比值大于 0.8 的最小照射时间。分位数回归显示，在置信水平为 95%时，达到测试/对照比值为 0.8 所需的照射时间分别为 41.5 秒和 39.2 秒，深度分别为 200 µm 和 500 µm 的水门汀。除了照射时间为 10 秒的情况外，两个深度的显微硬度没有统计学上的显著差异。两个部位到三个部位的光固化比较除了 90 秒时间外，没有统计学上的显著差异。
对于厚的间接修复体，通过唇侧、舌侧和咬合面进行系统性光固化并不总是需要充分聚合，甚至可能浪费宝贵的临床时间，尤其是在多个用树脂复合材料粘固的修复体的情况下。
