Department of Cariology and Endodontology, Peking University School and Hospital of Stomatology, Beijing, China.
Minnesota Dental Research Center for Biomaterials and Biomechanics, School of Dentistry, University of Minnesota, Minneapolis, USA.
Int Endod J. 2021 Sep;54(9):1638-1646. doi: 10.1111/iej.13530. Epub 2021 May 5.
To simulate in a laboratory setting longitudinal cracking in root filled premolar teeth, using cyclic mechanical fatigue.
Mesial-occlusal-distal (MOD) cavities were prepared in twenty root filled, single-rooted, mandibular premolars restored with fibre posts and resin composites. The samples were randomly divided into two groups based on the loading approaches: static loading with a crosshead speed of 0.5 mm/min and step-stress cyclic loading (1 Hz) with increasing amplitude. The loads and numbers of cycles to failure were recorded. Micro-CT was also used to identify the fracture modes. Statistical analysis was performed using Student's t-test. The level of significance was set at 0.05.
The mean fracture loads for the static loading and cyclic loading groups were 769 ± 171 N and 720 ± 92 N, respectively. There was no significant difference between the two groups (P > 0.05). The proportions of longitudinal, cuspal and mixed-mode fractures under cyclic loading were 50%, 20% and 30%, respectively. Longitudinal fractures occurred with larger numbers of cycles and higher average loads per cycle compared with the other fractures. Static loading produced only cuspal fractures.
Longitudinally cracked premolar teeth with root fillings were successfully produced using the step-stress cyclic loading method. This provides a more clinically representative methodology for studying cracked teeth in a laboratory setting.
使用循环机械疲劳在实验室环境中模拟根充前磨牙的纵向裂纹。
在 20 颗用纤维桩和树脂复合材料修复的根充、单根、下颌前磨牙的近中-颊舌-远中（MOD）腔中制备模型。根据加载方法将样本随机分为两组：以 0.5mm/min 的十字头速度进行静态加载和以 1Hz 递增幅度进行阶梯式循环加载。记录载荷和失效循环次数。还使用微 CT 来识别断裂模式。使用学生 t 检验进行统计分析。显著性水平设为 0.05。
静态加载组和循环加载组的平均断裂载荷分别为 769±171N 和 720±92N，两组之间无显著差异（P>0.05）。循环加载下的纵向、牙尖和混合模式骨折的比例分别为 50%、20%和 30%。与其他骨折相比，循环加载下的纵向骨折发生需要更多的循环次数和更高的平均循环载荷。静态加载仅产生牙尖骨折。
使用阶梯式循环加载方法成功制备了带根充的纵向裂纹前磨牙。这为在实验室环境中研究裂纹牙提供了一种更具临床代表性的方法。
