Baig Mirza Shahzad, Dowling Adam H, Fleming Garry J P
Materials Science Unit, Division of Oral Biosciences, Dublin Dental University Hospital, Lincoln Place, Trinity College Dublin, Dublin 2, Ireland.
J Dent. 2013 Nov;41(11):968-73. doi: 10.1016/j.jdent.2013.04.004. Epub 2013 Apr 12.
To investigate the load to failure of encapsulated posterior glass-ionomer (GI) restoratives tested under Hertzian indentation and to explore the validity and reproducibility of the test results achieved for consideration of inclusion as an ISO testing protocol.
Groups of 20 disc-shaped specimens (10.0±0.1mm diameter, 3.10±0.03mm thickness) were prepared (in batches of four) from three encapsulated posterior GI restoratives. Discs were tested while resting freely on a dentine analogue material at 24h under Hertzian indentation at a rate of 1mm/min delivered through a 20mm diameter hard steel ball. The failure mode and fracture origin of the GI specimens was assessed by fractography. Statistical analyses of the load to failure data were conducted using SPSS software (p<0.05) with the normality and homogeneity of variance of the load to failure data assessed using the Shapiro-Wilk and Levene's test, respectively. Data was also analysed using regression analyses to identify trends within the load to failure data sets.
The load to failure data for the GI restorative groups investigated were normally distributed (p>0.05), homogenous (p>0.05) and not significantly influenced by batch (p>0.780) or specimen number (p>0.447) although significant differences (p<0.05) between the GI restorative materials were evident. Fractographic analysis identified smooth fracture surfaces parallel to the loading axis where the failure mode was bottom initiated radial cracking. The mean coefficient of variation (CoV) for the GI restorative load to failure data sets achieved using Hertzian indentation testing was 7%.
The failure mode and fracture origin of the GI restoratives tested using Hertzian indentation is representative of the clinical situation in vivo. The reliability of the load to failure data sets produced were improved compared with routinely employed mechanical testing approaches suggesting the possibility of inclusion as an ISO testing protocol.
研究在赫兹压痕试验下封装型后牙玻璃离子（GI）修复材料的破坏载荷，并探讨所获试验结果的有效性和可重复性，以供考虑纳入ISO测试标准。
从三种封装型后牙GI修复材料制备20个圆盘形试件组（直径10.0±0.1mm，厚度3.10±0.03mm）（每组四个）。圆盘在24小时时自由放置在牙本质模拟材料上，通过直径20mm的硬钢球以1mm/分钟的速率进行赫兹压痕试验。通过断口分析评估GI试件的破坏模式和断裂起源。使用SPSS软件对破坏载荷数据进行统计分析（p<0.05），分别使用夏皮罗-威尔克检验和莱文检验评估破坏载荷数据的正态性和方差齐性。还使用回归分析对数据进行分析，以确定破坏载荷数据集中的趋势。
所研究的GI修复材料组的破坏载荷数据呈正态分布（p>0.05）、方差齐性（p>0.05），且不受批次（p>0.780）或试件数量（p>0.447）的显著影响，尽管GI修复材料之间存在显著差异（p<0.05）。断口分析确定了与加载轴平行的光滑断裂表面，破坏模式为底部起始的径向开裂。使用赫兹压痕试验获得的GI修复材料破坏载荷数据集的平均变异系数（CoV）为7%。
使用赫兹压痕试验测试的GI修复材料的破坏模式和断裂起源代表了体内临床情况。与常规使用的机械测试方法相比，所产生的破坏载荷数据集可靠性有所提高，表明有可能纳入ISO测试标准。
