Faculty of Stomatology, Capital Medical University, Beijing 100050, China） [Abstract] Objective To evaluate the effect of using dental operating microscope and ultrasonic instruments in treating blocked canals. Methods The etiology of canal blockage included calcification, broken instruments, posts, resinifying, etc. 236 blocked canals were treated with ultrasonic tips under dental operating microscope. The success rate was calculated. Results 178 blocked canals were successfully managed with a success rate of 75.4%. The success rate of each category of the blocked canals were: 71.7% for calcified canals, 81.1% for broken instruments, 100% for canals blocked by posts, 62.5% for canals blocked by resinifying therapy, and 84.1% for canals blocked by filling materials. Conclusion The use of dental operating microscope and ultrasonic instruments is proved to be an effective method in the management of blocked canals.
