关键词: 牙科手术显微镜, 器械折断, 分角投照技术, 数字根尖片, 根管侧穿

Abstract: Objective To explore the application value of digital periapical film to preoperative assessment of removing intracanal separated instruments. Methods Through analyzing digital periapical films with bisecting angle technique， this paper explored the relationship between intracanal position of separated instruments and the success rate of removing separated instruments or the incidence of root canal perforation. Results The successful rate of removing separated instruments in apical third of root canal was 36.84% and the incidence of root canal perforation was 52.63%;compared with the successful rate and the incidence of root canal perforation for separated instruments in coronal third and middle third of root canals， the difference was statistically significant （P < 0.05）. For those separated instruments below the curve of canal， the successful rate and the incidence of root canal perforation was 42.86%and 47.62%，but for those above curve of canal， the successful rate and the incidence of root canal perforation was 88.46% and 11.54%. Conclusion Digital periapical films with bisecting angle technique have important reference value for preoperative assessment of removing intracanal separated instruments， and can be used as a conventional method for preoperative difficulty assessment and prediction of perforation.

Key words: dental operating microscope, instrument separation, bisecting angle technique, digital periapical film, root canal perforation