不同模式下超声对牙根抗折性能影响研究

Effect of various modes of ultrasound on the fracture resistance of teeth

目的研究超声功率、工作尖工作范围和工作深度对牙根抗折性能的影响。方法收集2015年1—5月在中国医科大学附属口腔医院就诊患者因正畸治疗需要拔除的64颗下颌单根管前磨牙,建立根管桩修复模型。采用随机分组三因素两水平析因设计,按各因素不同水平排列组合,将64颗牙随机分为8组,每组8颗。各组牙齿均用P5 Newtron超声治疗仪配合ET20工作尖于桩周围振动去除牙本质后,置于万能力学试验机上加载直至折裂,记录牙根最大折裂力及折裂方式。对结果进行三因素析因设计资料的方差分析和卡方检验。结果方差分析结果显示,超声功率、工作尖工作范围和工作深度对牙根抗折性能均有显著影响(P<0.05);卡方检验结果显示,超声工作尖工作范围影响牙根折裂方向,工作深度影响牙根折裂部位(P<0.05)。结论本研究中超声功率、工作尖工作范围和工作深度均是影响牙根抗折力的因素。超声功率与工作范围、工作深度之间分别存在交互作用。

Objective To evaluate the influence of various ultrasonic power setting,working range and working depth on fracture resistance of teeth in vitro. Methods Totally 64 extracted human single-rooted mandible premolars were collected to construct the Root canal post＇s model. Factorial design with three factors and two levels was used. All the 64 teeth were randomly divided into 8 groups,8 in each group. Remove dentin around the post with P5 Newtron ultrasonic device and ET-20 ultrasonic tip. All teeth were mounted on the universal mechanical testing machine,and loaded vertically at 0.5 mm per minute until fracture. Fracture force and fracture patterns were recorded. The results were analyzed by three-factor factorial design ANOVA and chi-square test. Results There was a significant difference in fracture resistance among various ultrasonic power setting,working range and working depth（P 〈0.05）. The ultrasonic working range affected the direction of fracture and the ultrasonic working depth affected the site of frature（P 〈0.05）. Conclusion The different ultrasonic power setting,working range and working depth have significant influence upon fracture resistance of teeth. There are interactive effects between ultrasonic power setting and working range or ultrasonic power setting and working depth respectively.