Devale Madhuri R, Mahesh M C, Bhandary Shreetha
Postgraduate Student, Department of Conservative Dentistry and Endodontics, AECS Maaruti College of Dental Sciences , Bengaluru, Karnataka, India .
Professor, Department of Conservative Dentistry and Endodontics, AECS Maaruti College of Dental Sciences , Bengaluru, Karnataka, India .
J Clin Diagn Res. 2017 Jan;11(1):ZC15-ZC18. doi: 10.7860/JCDR/2017/22059.9159. Epub 2017 Jan 1.
Stresses generated during root canal instrumentation have been reported to cause apical cracks. The smaller, less pronounced defects like cracks can later propagate into vertical root fracture, when the tooth is subjected to repeated stresses from endodontic or restorative procedures.
This study evaluated occurrence of apical cracks with stainless steel hand files, rotary NiTi RaCe and K3 files at two different instrumentation lengths.
In the present in vitro study, 60 mandibular premolars were mounted in resin blocks with simulated periodontal ligament. Apical 3 mm of the root surfaces were exposed and stained using India ink. Preoperative images of root apices were obtained at 100x using stereomicroscope. The teeth were divided into six groups of 10 each. First two groups were instrumented with stainless steel files, next two groups with rotary NiTi RaCe files and the last two groups with rotary NiTi K3 files. The instrumentation was carried out till the apical foramen (Working Length-WL) and 1 mm short of the apical foramen (WL-1) with each file system. After root canal instrumentation, postoperative images of root apices were obtained. Preoperative and postoperative images were compared and the occurrence of cracks was recorded. Descriptive statistical analysis and Chi-square tests were used to analyze the results.
Apical root cracks were seen in 30%, 35% and 20% of teeth instrumented with K-files, RaCe files and K3 files respectively. There was no statistical significance among three instrumentation systems in the formation of apical cracks (p=0.563). Apical cracks were seen in 40% and 20% of teeth instrumented with K-files; 60% and 10% of teeth with RaCe files and 40% and 0% of teeth with K3 files at WL and WL-1 respectively. For groups instrumented with hand files there was no statistical significance in number of cracks at WL and WL-1 (p=0.628). But for teeth instrumented with RaCe files and K3 files significantly more number of cracks were seen at WL than WL-1 (p=0.057 for RaCe files and p=0.087 for K3 files).
There was no statistical significance between stainless steel hand files and rotary files in terms of crack formation. Instrumentation length had a significant effect on the formation of cracks when rotary files were used. Using rotary instruments 1 mm short of apical foramen caused lesser crack formation. But, there was no statistically significant difference in number of cracks formed with hand files at two instrumentation levels.
据报道，根管预备过程中产生的应力会导致根尖裂纹。像裂纹这样较小、不太明显的缺陷，在牙齿受到来自牙髓治疗或修复操作的反复应力时，随后可能会发展为垂直根折。
本研究评估了使用不锈钢手动锉、旋转镍钛RaCe锉和K3锉在两种不同预备长度下根尖裂纹的发生率。
在本体外研究中，60颗下颌前磨牙被固定在带有模拟牙周膜的树脂块中。牙根表面根尖3mm处暴露并用印度墨水染色。使用体视显微镜在100倍放大倍数下获取根尖术前图像。牙齿被分为六组，每组10颗。前两组用不锈钢锉进行预备，接下来两组用旋转镍钛RaCe锉，最后两组用旋转镍钛K3锉。每种锉系统的预备操作均进行至根尖孔（工作长度-WL）以及距根尖孔短1mm处（WL-1）。根管预备后，获取根尖术后图像。比较术前和术后图像并记录裂纹的发生率。采用描述性统计分析和卡方检验来分析结果。
分别使用K锉、RaCe锉和K3锉预备的牙齿中，根尖根裂纹的发生率分别为30%、35%和20%。在根尖裂纹形成方面，三种预备系统之间无统计学意义（p=0.563）。在WL和WL-1处，使用K锉预备的牙齿中根尖裂纹发生率分别为40%和20%；使用RaCe锉的牙齿中分别为60%和10%；使用K3锉的牙齿中分别为40%和0%。对于使用手动锉预备的组，WL和WL-1处裂纹数量无统计学意义（p=0.628）。但对于使用RaCe锉和K3锉预备的牙齿，WL处的裂纹数量明显多于WL-1处（RaCe锉p=0.057，K3锉p=0.087）。
在裂纹形成方面，不锈钢手动锉和旋转锉之间无统计学意义。当使用旋转锉时，预备长度对裂纹形成有显著影响。在距根尖孔短于1mm处使用旋转器械导致的裂纹形成较少。但是，在两个预备长度水平下，使用手动锉形成的裂纹数量无统计学显著差异。
