Hospital of Stomatology, Sun Yat-sen University, Guangzhou, China; Guangdong Provincial Key Laboratory of Stomatology, Guangzhou, China; Guanghua School of Stomatology, Sun Yat-sen University, Guangzhou, China.
The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.
Dent Mater. 2022 Oct;38(10):1575-1586. doi: 10.1016/j.dental.2022.07.008. Epub 2022 Aug 5.
(1) To identify improvements when bulk compressive creep testing of dental resin composite materials to reduce the sensitivity to the surface morphology and parallelism of specimens, to generate more accurate strain (displacement) measurement values. (2) To investigate the effect of loading rate on the creep and recovery behavior under bulk compressive creep test.
Cylindrical composite resin specimens were subjected to bulk compressive creep test with conventional and modified methodology (with/without introduction of stainless steel hemisphere and preload process). Furthermore, specimens undertook different loading rates ranging from 1 N/s to 50 N/s. Maximum deformation, creep deformation, permanent set as well as percentage of recovery during the creep and recovery procedure were compared, and surface topography changes before and after preload process was evaluated by laser scanning confocal. Burgers model was used to investigate the effect of improvements to each part of viscoelastic deformation of resin specimens.
(1) The influence of surface evenness of resin specimens could be reduced by addition of preload process before the bulk compressive creep test resulting in significantly decreased permanent set (p = 0.002), and increased recovery to 91.7 % (p < 0.001). While the standard deviation of maximum deformation, permanent set and percentage of recovery had the smallest values when hemisphere was introduced to loading chain. (2) With increasing loading rate of bulk compressive creep tests, creep deformation increased and this trend became statistically significant when the loading rate reached 50 N/s.
The accuracy of deformation measurement during bulk compressive creep test could be improved by means of introducing stainless steel hemisphere to the loading chain, and adding preload process to loading protocol.
（1）通过对牙科树脂复合材料进行整体压缩蠕变测试，以减少对试件表面形貌和平行度的敏感性，从而提高测试的准确性。（2）研究在整体压缩蠕变测试中加载速率对蠕变和恢复行为的影响。
采用传统和改进的方法（有/无引入不锈钢半球和预载过程）对圆柱形复合树脂试件进行整体压缩蠕变测试。此外，试件还进行了不同的加载速率，范围从 1N/s 到 50N/s。比较了最大变形、蠕变变形、永久变形以及蠕变和恢复过程中的恢复百分比，并通过激光扫描共聚焦评估了预载过程前后的表面形貌变化。使用 Burgers 模型研究了改进树脂试件粘弹性变形各部分对蠕变和恢复行为的影响。
（1）通过在整体压缩蠕变测试前增加预载过程，可以减少树脂试件表面平整度的影响，从而显著降低永久变形（p=0.002），并使恢复率提高到 91.7%（p<0.001）。而当在加载链中引入半球时，最大变形、永久变形和恢复百分比的标准偏差具有最小的值。（2）随着整体压缩蠕变测试加载速率的增加，蠕变变形增加，当加载速率达到 50N/s 时，这种趋势具有统计学意义。
通过在加载链中引入不锈钢半球并在加载方案中增加预载过程，可以提高整体压缩蠕变测试中变形测量的准确性。
