Reduction of polymerization contraction stress for dental composites by two-step light-activation
Reduction of polymerization contraction stress for dental composites by two-step light-activation
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DOI：
10.1016/s0109-5641(01)00066-5
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发表时间：
2002-09-01
期刊：
影响因子：
5
通讯作者：
Condon, JR
中科院分区：
文献类型：
--
作者：
Lim, BS;Ferracane, JL;Condon, JR
目的：本研究的目的是评估在两步光活化过程中复合材料的聚合收缩应力的减少，并将这种减少与聚合收缩和试样厚度的过程联系起来。方法：进行三个测试程序来比较两步光活化延迟与一步连续照射复合材料：使用闭环伺服液压测试仪器测量聚合收缩应力，通过水银粘度计测量聚合收缩，通过FTIR测量转化度。对于一步连续固化方法，将样品在330 mW/cm（2）下光活化60 s。对于两步固化方法，在60 mW/cm（2）下曝光5 s，然后不曝光2 min，然后在330 mW/cm（2）下第二次曝光60 s。相同的光参数用于测量应力、收缩。和转化程度。评价了三种复合材料，Heliomolar、Herculite和2100。结果：光活化后10 min，两步法可显著降低聚合收缩应力（P < 0.05）：Heliomolar为29.7%，Herculite为26.5%，Z100为19.0%。总体积收缩率和转换程度没有显着不同的复合材料固化的两种不同的技术。增加复合材料样品的厚度降低了测量的收缩应力，特别是对于两步固化methods.Significance之一：低初始能量密度的组合，然后由一个滞后期，然后再最终高强度的光照射提供了一个减少聚合收缩应力在牙科复合材料。应力降低不能归因于转化程度的降低或无限制的体积收缩。(C)2002年牙科材料学院。由Elsevier Science Ltd.出版，版权所有。
Objectives: The goal of this study was to assess the reduction of polymerization contraction stress of composites during a two-step light-activation process and to relate this reduction to the process of polymerization shrinkage and specimen thickness.Methods: Three test procedures were performed to compare two-step light-activation with delay with one-step continuous irradiation of composites: polymerization contraction stress using a closed-loop servohydraulic testing instrument, polymerization shrinkage by a mercury dilatometer, and degree of conversion by FTIR. For the one-step continuous curing method, the samples were light-activated for 60 s at 330 mW/cm(2). For the two-step curing method, a 5 s light exposure at 60 mW/cm(2) was followed by 2 min without light exposure, and then a second light exposure for 60 s at 330 mW/cm(2). The same light parameters were used for measurements of stress, shrinkage. and degree of conversion. Three composites, Heliomolar, Herculite and 2100 were evaluated. The contraction stress experiments were repeated with varying thickness for Herculite using the one-step and two different two-step techniques.Results: Polymerization contraction stress 10 min after light-activation was significantly reduced (P < 0.05) by the two-step method: 29.7% for Heliomolar, 26.5% for Herculite, and 19.0% for Z100. Total volumetric shrinkage and degree of conversion were not significantly different for composites cured by the two different techniques. Increasing the thickness of the composite sample reduced the measured contraction stress, especially for one of the two-step curing methods.Significance: A combination of low initial energy density followed by a lag period before a final high-intensity light irradiation provides a reduction of polymerization contraction stresses in dental composites. The stress reductions cannot be attributed to reductions in degree of conversion or unrestrained volumetric shrinkage. (C) 2002 Academy of Dental Materials. Published by Elsevier Science Ltd. All rights reserved.