Objectives

To evaluate the effect of time on the Vickers microhardness (VH) at the top and bottom surfaces of six conventional resin-based composites (RBCs) up to twelve weeks after light curing.

Methods

Five specimens of Filtek Supreme Ultra, Herculite Ultra, Mosaic Ultra, Tetric EvoCeram, TPH Spectra HV, and Venus Pearl were packed into opaque molds that were 2.3 mm in diameter and 2.5 mm deep. The uncured RBC specimens were covered by a polyester strip and photo-cured with an Elipar DeepCure-S light-curing unit (LCU) according to the manufacturer's instructions. After irradiation, the polyester strip was removed, and the Vickers microhardness was measured immediately at top and bottom surfaces. The hardness measurements were repeated after 30 min, 1 h, 2 h, 4 h, 24 h, 1 week, 4 weeks, and 12 weeks. In between, the specimens were stored in dry and dark conditions at 37 °C. Two-way ANOVA (α = 0.05) followed by Tukey–Kramer post hoc multiple comparison tests were used to determine where statistically significant differences existed.

Results

The micro-hardness values at the top surface always exceeded those at the bottom surface. A significant logarithmic increase of the micro-hardness due to post-irradiation curing took place between 30 min and 24 h (p < 0.05). There was no significant increase in the VH after 24 h. Depending on the RBC, compared to the immediate values the hardness 24 h post-irradiation had increased by 11–27% at the top surface and by 21–58% at the bottom.

Significance

Even after 12 weeks, the bottom hardness values never reached the top microhardness values. The results of studies that wait 24 h or longer before measuring the properties of RBC specimens will be significantly enhanced by the impact of post-irradiation curing. Especially within the first 4 h, the time when specimens are measured is critical information and should be reported.

中文翻译：

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时间对六种树脂基复合材料辐照后固化的影响。

目标

为了评估时间对光固化后长达十二周的时间的影响，对六种常规树脂基复合材料（RBC）的顶部和底部表面的维氏显微硬度（VH）产生影响。

方法

将Filtek Supreme Ultra，Herculite Ultra，Mosaic Ultra，Tetric EvoCeram，TPH Spectra HV和Venus Pearl的五个标本装入不透明的模具中，该模具直径为2.3毫米，深度为2.5毫米。未固化的RBC样品用聚酯条覆盖，并根据制造商的说明用Elipar DeepCure-S光固化装置（LCU）光固化。辐照后，除去聚酯条，并立即在顶部和底部表面测量维氏显微硬度。在30分钟，1小时，2小时，4小时，24小时，1周，4周和12周后重复进行硬度测量。在这之间，将标本存储在37°C的干燥和黑暗条件下。两向方差分析（α = 0.05），然后采用Tukey–Kramer事后多重比较测试确定存在统计学差异的地方。

结果

顶表面的显微硬度值始终超过底表面的显微硬度值。在30分钟至24小时之间，由于辐照后固化，显微硬度显着对数增加（p  <0.05）。24小时后，VH没有明显增加。取决于RBC，与即刻值相比，辐照后24 h的硬度在上表面增加了11–27％，在底部增加了21–58％。

意义

即使在12周之后，底部硬度值也从未达到顶部显微硬度值。在辐照后固化的影响下，等待24小时或更长时间才能测量RBC标本性能的研究结果将大大增强。特别是在最初的4小时内，测量样本的时间是关键信息，应予以报告。