Faculty of Medical Dentistry, Mohammed V University, Rabat, Morocco, Phone: +212 662222918, e-mail:
Faculty of Medical Dentistry, Mohammed V University, Rabat, Morocco.
J Contemp Dent Pract. 2021 Mar 1;22(3):259-263.
The aim of this study was to compare the formation of dentinal cracks with nickel-titanium (NiTi) instruments working in continuous rotation and reciprocating motion.
One hundred sixty extracted human mandibular first molars were selected for the study. The mesial roots were resected and mounted in resin blocks with simulated periodontal ligaments. Those teeth were randomly assigned to five groups ( = 32 teeth/group). The first one was treated with -files and served as control group, and the remaining 128 teeth were divided into 4 groups depending on the root canal preparation technique. Group 2 samples were prepared by sequential ProTaper Universal (PTU), group 3 samples with rotary ProTaper Universal (RPTU), group 4 achieved by the One Shape (OS), and group 5 with the WaveOne (WO) primary files. Roots were then horizontally sectioned at 3, 6, and 9 mm from the apex, and the slices were then observed under a stereomicroscope at ×40 magnification to determine the presence of internal dentinal microcracks. The presence or absence of dentinal defaults was recorded and the statistical analysis was performed by Pearson Chi-square test. The significance level was set at < 0.05. The study was made in the oral biology and biotechnology research laboratory of the faculty of medical dentistry of Rabat, Morocco.
No dentinal defect was seen with the stainless steel hand file (group 1). The manual PTU (group 2), the RPTU (group 3), the OS (group 4), and the WO (group 5) in reciprocating motion caused cracks in 15.6%, 12.4%, 21.9%, and 6.2% of samples, respectively. The highest percentage of dentinal defect was showed in group 4 but without significant difference with the other group ( > 0.05).
Dentinal cracks are produced indifferently of motion kinematics. Within the limits of this study and the current literature, such incidence is less with instruments working in reciprocating motion compared with those working in continuous rotation. Manual and rotary NiTi sequential systems showed fewer microcracks than the single file system working by continuous rotation motion.
本研究的目的是比较镍钛（NiTi）器械在连续旋转和往复运动中形成牙本质裂纹的情况。
选择 160 颗下颌第一磨牙进行研究。将近中根切除并安装在带有模拟牙周韧带的树脂块中。这些牙齿被随机分为五组（每组 32 颗牙）。第一组用锉刀处理作为对照组，其余 128 颗牙根据根管预备技术分为四组。第 2 组用逐步 ProTaper Universal（PTU）预备，第 3 组用旋转 ProTaper Universal（RPTU）预备，第 4 组用 One Shape（OS）预备，第 5 组用 WaveOne（WO）主锉预备。然后将牙根从根尖 3、6 和 9mm 处水平切片，在立体显微镜下以×40 放大倍数观察切片，以确定是否存在内部牙本质微裂纹。记录牙本质缺陷的存在或不存在，并通过 Pearson Chi-square 检验进行统计学分析。显著性水平设定为 < 0.05。该研究在摩洛哥拉巴特医学牙科学院口腔生物学和生物技术研究实验室进行。
不锈钢手用锉（第 1 组）未见牙本质缺陷。手动 PTU（第 2 组）、RPTU（第 3 组）、OS（第 4 组）和 WO（第 5 组）在往复运动中分别导致 15.6%、12.4%、21.9%和 6.2%的样本出现裂纹。第 4 组牙本质缺陷率最高，但与其他组无显著差异（> 0.05）。
牙本质裂纹的产生与运动运动学无关。在本研究和现有文献的范围内，与连续旋转运动的器械相比，往复运动的器械产生牙本质裂纹的发生率较低。手动和旋转镍钛连续系统比连续旋转运动的单锉系统显示出更少的微裂纹。
