Objective

This study utilizes micro-CT image combined with finite element (FE) analysis and in vitro fatigue testing to investigate the mechanical behavior associating with early resin luting cement damage induced by voids around a circular fiber post in a root canal treated premolar.

Methods

Six similar mandibular first premolars with root canal treatment were scanned with high resolution micro-CT before and after fatigue testing. Micro-CT images of all teeth were processed to identify various materials (dentin, luting cement and void) to evaluate the volume/position of the void in each reconstructed tooth root canal model. Six corresponding mesh models from CT images were generated to perform FE simulations under receiving oblique concentrated loads (200 N) to evaluate the luting cement layer mechanical behavior. All teeth were subjected to the fatigue test with 240,000 load cycles simulating chewing for one year to compare results with those in FE simulations.

Results

The result showed that most voids occurred adjacent to the apical third of the fiber post. Voids induced the fiber post to pull out, creating a stress concentration at the void boundary. Fatigue life in the experimental testing was found decreased with the stress value/micro-motion increasing in FE analysis.

Significance

This study establishes that micro-CT, FE simulation and fatigue testing can be integrated to understand the early de-bonding mechanism at the luting cement layer in a root canal treated premolar, suggesting that attention must be paid to resin luting cement dissolving/debonding easier when voids occur in the apical and peri-apical areas of fiber posts.

中文翻译：

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结合微型CT，有限元分析和疲劳测试，评估根管治疗后的前磨牙中圆形纤维桩周围空隙引起的树脂早期胶结水泥损坏

客观的

这项研究利用显微CT图像结合有限元（FE）分析和体外疲劳测试来研究与根管治疗后的前磨牙中圆形纤维柱周围空隙引起的早期树脂腐蚀水泥损坏相关的力学行为。

方法

在疲劳测试之前和之后，用高分辨率的micro-CT扫描六个类似的下颌第一前磨牙并进行根管治疗。对所有牙齿的Micro-CT图像进行处理，以识别各种材料（牙质，牙结石和空隙），以评估每个重建的牙根管模型中空隙的体积/位置。从CT图像生成了六个相应的网格模型，以在承受斜向集中载荷（200 N）的情况下进行有限元模拟，以评估胶结水泥层的机械性能。所有牙齿均经受了240,000个负载周期的疲劳测试，模拟了咀嚼一年，以将其结果与有限元仿真中的结果进行比较。

结果

结果表明，大多数空隙发生在纤维柱顶端的三分之一附近。空隙导致纤维柱拉出，在空隙边界处产生应力集中。在有限元分析中，发现实验测试中的疲劳寿命随着应力值/微运动的增加而降低。

意义

这项研究建立了微CT，有限元模拟和疲劳测试可以整合在一起，以了解根管处理过的前磨牙的粘固水泥层的早期脱胶机理，这表明必须注意使树脂粘固水泥更容易溶解/脱粘当纤维桩的根尖和根尖区域出现空隙时。