Abstract:

Abstract：Objective To locate the ideal position of straight-line endodontic access opening to mandibular incisors and evaluate the influence of different access opening on the curvature degree of endodontic instruments. Methods Self-control was designed in the research. Totally 82 extracted mandibular permanent incisors were opened to pulp with labial access after traditional lingual access，then stainless K file was inserted separately from lingual and labial to radiograph from proximalview and digital films obtained. Then two indexes between labial access group and traditional lingual access group about canal access angle（CAA）and angle of curvature（AOC）were compared，and the ideal endodontic access was located when the K file was straight in the root canal. Results The ideal endodontic access to the mandibular incisors was mainly located at the incisal edge in 73.17%，whereas at the labial side in 25.61% and at the lingual side only in 1.22%.The angles of the same teeth about CAA and AOC with labial access opening were both lower than those with lingual access opening（P < 0.05）. Conclusion It is recommended in the root canal therapy for mandibular incisor that using labial even incisal margin access opening can lower the curvature of instrument in the root canal，and make the therapy easier.

Key words: mandibular permanent incisors, straight-line endodontic access, canal access angle, angle of curvature

摘要：

目的 研究下颌恒切牙根管路径成直线时的最佳开髓位置以及不同开髓法对根管器械弯曲程度的影响。方法 采用自身对照法，将2010—2011年山西省人民医院口腔中心拔除的82颗离体下颌恒切牙先后行传统舌侧开髓（舌侧开髓组）和唇侧开髓（唇侧开髓组），分别插不锈钢K锉拍近远中向投照的数字化牙片，分析舌侧开髓组器械在根管内成直线时的开髓位置，比较两组器械根管入角和器械在根管内的弯曲角度。结果 下颌恒切牙的最佳开髓位置在唇侧者占25.61%，位于切缘者占73.17%，位于舌侧者仅占1.22%；下颌恒切牙采用唇侧开髓后器械的根管入角和弯曲角度均小于舌侧开髓（P < 0.05）。结论 下颌恒切牙采用唇侧甚至切缘开髓可减小根管器械的弯曲程度，降低根管治疗的难度。

关键词: 下颌恒切牙, 直线路径, 根管入角, 弯曲角度