关键词: 下颌恒切牙, 直线路径, 根管入角, 弯曲角度

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