Jeon In-Soo, Spångberg Larz S W, Yoon Tai-Cheol, Kazemi Reza B, Kum Kee-Yeon
Yonsei University, Department of Endodontics, College of Dentistry, Oral Science Research Center, Seoul, South Korea.
Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003 Nov;96(5):601-7. doi: 10.1016/s1079-2104(03)00303-2.
The design of the cutting blade of rotary instruments may affect the outcome of root canal instrumentation in terms of cleanliness. The aim of this scanning electron microscopic study was to compare the quality and amount of smear layer generated in the apical third of straight root canals by 2 rotary nickel-titanium reamers and 1 rotary steel reamer with different cutting blade designs.
Seventy intact, single-rooted human mandibular premolars with straight, fully developed roots were selected for this study. Before instrumentation, the cervical portion of all teeth was removed by using a microtome (Isomet), leaving 13-mm-long roots. Automated preparation was performed with ProFile (n = 20) and Hero 642 (n = 20) reamers by using the crown-down technique and with a stainless steel engine reamer (Mani; n = 20) by using a reaming motion. All root canals were instrumented to No. 40. A control group (pulp extirpation with barbed broaches; n = 10) was also included. Irrigation with 3 mL of a 1% sodium hypochlorite (NaOCl) solution was performed after each instrumentation. After the instrumentation, each root was split longitudinally, and a scanning electron microscope was used to examine the selected areas of the canal walls at the apical third from 2 different perspectives. A 4-category scoring system for smear layer was used, and the resulting scores were statistically analyzed.
The least smear layer remained in the Hero 642 group at the selected apical third of straight root canals (P < .05). However, all instruments left a smear layer. The surface texture of the smear layer, in addition to the depth and the frequency of packed materials into the dentinal tubules, varied with instrument type.
These data revealed that the design of the cutting blade of rotary instruments can affect root canal cleanliness in straight root canals. This information may be useful in the selection of nickel-titanium rotary reamers.
旋转器械切割刃的设计可能会在清洁度方面影响根管预备的效果。本扫描电子显微镜研究的目的是比较2种旋转镍钛扩孔钻和1种具有不同切割刃设计的旋转钢质扩孔钻在直根管根尖三分之一处产生的玷污层的质量和数量。
本研究选取了70颗完整的、单根的、牙根笔直且发育完全的人下颌前磨牙。在进行预备之前，使用切片机（Isomet）去除所有牙齿的颈部部分，留下13毫米长的牙根。使用冠向下技术，用ProFile（n = 20）和Hero 642（n = 20）扩孔钻进行自动化预备，并用不锈钢机用扩孔钻（Mani；n = 20）进行扩锉动作。所有根管均预备至40号。还纳入了一个对照组（用倒刺锉进行牙髓摘除；n = 10）。每次预备后用3毫升1%次氯酸钠（NaOCl）溶液冲洗。预备完成后，将每个牙根纵向劈开，并用扫描电子显微镜从2个不同角度检查根尖三分之一处根管壁的选定区域。使用了一个4级玷污层评分系统，并对所得分数进行统计学分析。
在直根管选定的根尖三分之一处，Hero 642组留下的玷污层最少（P <.05）。然而，所有器械都留下了玷污层。玷污层的表面纹理，以及牙本质小管内充填材料的深度和频率，因器械类型而异。
这些数据表明，旋转器械切割刃的设计会影响直根管的根管清洁度。该信息可能有助于镍钛旋转扩孔钻的选择。
