Towards the elucidation of shrinkage stress development and relaxation in dental composites
Towards the elucidation of shrinkage stress development and relaxation in dental composites
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DOI：
10.1016/j.dental.2004.05.002
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发表时间：
2004-12-01
期刊：
影响因子：
5
通讯作者：
Bowman, CN
中科院分区：
文献类型：
--
作者：
Lu, H;Stansbury, JW;Bowman, CN
目的：虽然已经提出并研究了各种旨在通过流动部分缓解收缩应力的光固化技术，但对应力松弛行为的直接监测和观察很少受到关注。在这项研究中，研究了应力松弛行为的阐明及其对整体应力发展的影响。方法：利用一种新型实验装置，能够对同一样品进行实时、同时的收缩应力和双键转化测量。结果：辐照60 s后，Bis-GMA/TEGDMA复合材料的收缩应力和转化率达到最高值（67.9 ± 1.2%）和收缩应力（2.9 ± 0.1 MPa）。收缩应力松弛现象，只观察到玻璃化前，这只适用于部分固化2或3秒的标本;照射2秒的标本表现出最大的能力，以减轻应力（约40%）。然而，为了实现这一点，与临床实际时间尺度相比，需要更长的固化后应力松弛时间。对于辐照6、10或60 s的试样，大部分收缩应力在玻璃化阶段期间和之后产生，并且没有观察到明显的应力松弛。尽管已经观察到玻璃化阶段之前的应力松弛，但是该研究表明，它并没有为降低总体收缩应力提供显著的益处，因为为了实现临床相关的转化，大部分收缩应力在玻璃化阶段期间和之后产生，这不允许在本研究中使用的时间尺度上应力松弛。(C)2004年牙科材料学院。由爱思唯尔有限公司出版。保留所有权利。
Objective: Although various photo-curing techniques aiming to partially relieve the shrinkage stress by flow have been proposed and investigated, the direct monitoring and observation of stress relaxation behavior received little attention. In this study, the elucidation of stress relaxation behavior and its impact on the overall stress development were investigated.Methods: A novel experimental set-up capable of real-time, simultaneous shrinkage stress and double bond conversion measurements on the same sample was utilized. The coupled shrinkage stress and conversion for specimens of a barium glass filled Bis-GMA/TEGDMA composite were continuously monitored during and after irradiation for various intervals (2, 3, 6, 10 and 60 s).Results: Specimens irradiated for 60 s reached the highest conversion (67.9+/-1.2%) and shrinkage stress (2.9+/-0.1 MPa). Shrinkage stress relaxation phenomena were only observed prior to vitrification, which only applied to specimens partially cured for 2 or 3 s; specimens irradiated for 2 s exhibit the largest capability to relieve stress (approximately 40%). However, to achieve this a much Longer post-cure stress relaxation time is required as compared to clinically practical time scales. For specimens irradiated for 6, 10 or 60s, the majority of the shrinkage stress is developed during and after the vitrification stage, and no appreciable stress relaxation can be observed.Significance: Although stress relaxation prior to vitrification stage has been observed, this study revealed that it did not provide a significant benefit towards the reduction of overall shrinkage stress since, to achieve clinically relevant conversion, the majority of the shrinkage stress is developed during and after the vitrification stage, which does not permit stress relaxation on the time scales used in this study. (C) 2004 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.