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

doi:10.12016/j.issn.2096-1456.2021.06.003

Abstract

Abstract:

Objective To study the computational fluid dynamics (CFD) characteristics of ultrasonic root canal irrigation when the file was placed at a certain depth in the root canal, to provide a reference for clinical application. Methods First, scanning laser vibrometry (SLV) was utilized to analyze the characteristics of vibrational ultrasonic files under 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 images of the results were obtained by FLUENT 18.0 software. Volume fraction, flow velocity and pressure in the root canal 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 irrigating 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.

Key words: root canal therapy, ultrasonic root canal irrigation, root canal irrigant, cavitation, computational fluid dynamics, scanning laser vibrometry, vibration, apical pressure

摘要：

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。

关键词: 根管治疗, 根管超声冲洗, 根管冲洗液, 空化, 计算流体动力学, 扫描激光振测法, 振动, 根尖压力

CLC Number:

XING Xiaoyu,LI Yanping,ZHANG Lin,HE Lina,LIU Huimei,NIU Yumei. Computational fluid dynamics analysis of the flow of ultrasonic irrigations in root canal[J]. Journal of Prevention and Treatment for Stomatological Diseases, 2021, 29(6): 377-382.

邢小宇,李艳萍,张琳,何丽娜,刘会梅,牛玉梅. 根管超声冲洗的计算流体动力学分析[J]. 口腔疾病防治, 2021, 29(6): 377-382.

Figures/Tables 5

Figure 1 Schematic diagram of geometric model of root canal and ultrasonic file h: distance between the physiological apical foramen and the anatomical apical foramen, h1: distance between the ultrasonic working tip and the physiological apical foramen, l1: the working length of the root canal; Φ: the diameter of the root canal

Figure 2 Measurement results of vibration of ultrasonic working file by scanning laser vibrometry a: three-dimensional axis, the negative direction of the X-axis is the direction of the root canal, which corresponds to the direction of gravity; b: vibration frequency and amplitude of an ultrasonic file; c: schematic diagram of ultrasonic tip movement trajectory

Figure 3 The vapor volume fraction on the X-Y axis of the irrigation fluid in the root canal when the ultrasonic tip was 1 mm away from the root tip The outermost periphery represents the root canal wall, the inner gray part represents the ultrasonic tip, and the gap between the two represents the root canal irrigation fluid. The color of the rinse fluid represents the value of the vapor

Figure 4 The velocity on the X-Y axis of the irrigation fluid in the root canal when the ultrasonic tip is 1 mm away from the root tip a: cloud diagram, the outermost periphery represents the root canal wall, the inner gray part represents the ultrasonic tip, and the gap between the two represents the root canal irrigation fluid, the color of the rinse fluid represents the value of the speed value; b: distribution of irrigant velocity as a function of position on the X-Y plane, velocities higher than 0.1 m/s (horizontal red line) are considered to be clinically effective

Figure 5 Apical pressure on the X-Y axis of the irrigation fluid in the root canal when the ultrasonic tip was 1 mm away from the root tip The outermost periphery represents the root canal wall, the inner gray part represents the ultrasonic tip, and the gap between the two represents the root canal irrigation fluid. The color of the rinse fluid represents the value of the apical pressure

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