根管超声冲洗的计算流体动力学分析

Computational fluid dynamics analysis of the flow of ultrasonic irrigations in root canal

目的应用计算机模型分析当超声工作尖位于根管内一定深度时冲洗液的计算流体动力学特点,以期为临床应用提供参考。方法首先使用扫描激光振测系统扫描超声工作尖,分析其在一定功率下的振动特点。然后应用ICEM CFD 18.0软件建立根管超声冲洗模型,设置超声工作尖放置的位置为距根尖止点1 mm,通过FLUENT 18.0软件获取结果云图,分析冲洗液的空化体积分数、流动速度及其对根尖压力。结果超声工作尖振动是以横向振动为主伴轻微的纵向振动;工作尖各部分横向振动的幅度均不同,工作尖尖端振幅最大,越靠近锉基部,振幅越小。冲洗液空化体积分数大于0的区域集中在工作尖周围;在工作尖周围冲洗液流速较大,最高达2 m/s,在工作尖前方约0.2 mm内,冲洗液流速大于0.1 m/s,而在距根尖0.8 mm范围内,冲洗液流速较小甚至为0;根尖压力为非正压。结论根据实验结果推断,当超声工作尖放在距根尖1 mm处时,冲洗液不会溢出根尖孔,冲洗过程相对安全;同时冲洗液在工作尖前方约0.2 mm内冲洗作用较强。

Objective To study the computational fluid dynamics(CFD)characteristics of ultrasonic root canal irri⁃gation when the file was placed at a certain depth in the root canal,to provide a reference for clinical application.Meth⁃ods First,scanning laser vibrometry(SLV)was utilized to analyze the characteristics of vibrational ultrasonic files un⁃der specific power.Then ICEM CFD 18.0 software was used to establish the root canal ultrasonic irrigation model.The insertion position of the ultrasonic working tip was set 1 mm away from the physiological apical foramen,and cloud im⁃ages of the results were obtained by FLUENT 18.0 software.Volume fraction,flow velocity and pressure in the root ca⁃nal were evaluated after setting the computing conditions.Results The vibration of the ultrasonic working tip was mainly transverse vibration with slight longitudinal vibration.The amplitude of transverse vibration of each part of the working tip was different.Maximum values were observed at the apical end area of the file,and the closer to the base of the file,the smaller the amplitude.The area where the cavitation volume fraction of the rinsing fluid was greater than 0 was concentrated around the working point.The flow rate of the irrigating fluid was up to 2 m/s,within the area 0.2 mm in front of the working tip,the velocity of the irrigating fluid was greater than 0.1 m/s,while within the area 0.8 mm from the root tip,the velocity of the irrigating fluid was small or even zero.The apical pressure value was non⁃positive when the tip of the file was 1 mm away from the apical foramen in this model.Conclusion Based on the experimental results,it appears that when the ultrasonic working tip was placed 1 mm short of the working length,the ultrasonic irri⁃gating flow did not overflow the root apical foramen and the irrigation process was relatively safe;the irrigation fluid had a strong irrigation effect within approximately 0.2 mm in front of the working tip.