Han Bing, Wang Xiao yan, Gao Xue jun
Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing 100081, China.
Beijing Da Xue Xue Bao Yi Xue Ban. 2011 Feb 18;43(1):58-61.
The purpose of this study was to investigate the effect of light power density on anti-aging property of composite resins.
Three light curing modes with different power density (1. Mode A: low power density, 500 mW/cm(2) for 22 s; 2. Mode B: high power density, 1 100 mW/cm(2) for 10 s; 3. Mode C: gradually enhanced power density, 0~650 mW/cm(2) for 5 s + 1 100 mW/cm(2) for 8.5 s) were used. The total energy density of these modes was all 11 J/cm(2). Composite resin specimens were cured with three light curing modes respectively and divided into 4 groups randomly (n=15). Three groups were reserved in absolute ethanol for 24 h, 7 d and 30 d respectively for aging and one group was stored in water for 24 h as control. Vicker hardness (VHN) was measured with microhardness tester. Volumetric shrinkage was measured with Acuvol (n=7).
The hardness of three light curing modes was: Mode A 44.26±6.16, Mode B 42.31±2.33 and Mode C 45.60±2.76. After aging in ethanol for 24 h, the hardness of all composites specimen decreased (P<0.05). Samples cured by Mode A (31.83±2.90) and Mode C (32.13±2.77) showed significantly lower hardness than Mode B (36.14±2.65) (P<0.05). After aging in ethanol for 7 d, the hardness of composites continuously decreased (P<0.05) and was: Mode A 28.36±2.35, Mode B 27.80±1.19 and Mode C 28.20±0.97. There was no significant difference among three curing modes (P>0.05). The hardness of samples stored in ethanol for 30 d was no longer decreased and was: Mode A 28.53±0.86, Mode B 28.55±1.53 and Mode C 29.08±1.60. There was no significant difference between composite specimen stored for 7 d and 30 d (P>0.05). The polymerization shrinkage of composite resin was: Mode A 2.67%±0.28%, Mode B 2.76%±0.29% and Mode C 2.73%±0.06%. No significant difference existed among polymerization shrinkage of composites cured by the three light curing modes with different power density (P>0.05).
The power density of curing light affected the anti-aging property of composite resin which was aging time dependent. The polymerization shrinkage was not affected by light power density with same energy density.
本研究旨在探讨光功率密度对复合树脂抗老化性能的影响。
采用三种不同功率密度的光固化模式（1. A模式：低功率密度，500 mW/cm² 持续22秒；2. B模式：高功率密度，1100 mW/cm² 持续10秒；3. C模式：功率密度逐渐增强，0至650 mW/cm² 持续5秒 + 1100 mW/cm² 持续8.5秒）。这些模式的总能量密度均为11 J/cm²。复合树脂标本分别采用三种光固化模式固化，并随机分为4组（n = 15）。三组分别在无水乙醇中保存24小时、7天和30天进行老化，一组在水中保存24小时作为对照。用显微硬度计测量维氏硬度（VHN）。用Acuvol测量体积收缩率（n = 7）。
三种光固化模式的硬度分别为：A模式44.26±6.16，B模式42.31±2.33，C模式45.60±2.76。在乙醇中老化24小时后，所有复合树脂标本硬度均下降（P<0.05）。A模式（31.83±2.90）和C模式（32.13±2.77）固化的标本硬度显著低于B模式（36.14±2.65）（P<0.05）。在乙醇中老化7天后，复合树脂硬度持续下降（P<0.05），分别为：A模式28.36±2.35，B模式27.80±1.19，C模式28.20±0.97。三种固化模式之间无显著差异（P>0.05）。在乙醇中保存30天的标本硬度不再下降，分别为：A模式28.53±0.86，B模式28.55±1.53，C模式29.08±1.60。保存7天和30天的复合树脂标本之间无显著差异（P>0.05）。复合树脂的聚合收缩率分别为：A模式2.67%±0.28%，B模式2.76%±0.29%，C模式2.73%±0.06%。三种不同功率密度光固化模式固化的复合树脂聚合收缩率之间无显著差异（P>0.05）。
固化光的功率密度影响复合树脂的抗老化性能，且与老化时间相关。相同能量密度下，聚合收缩率不受光功率密度影响。
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