Abstract：Objective To explore the use of dental operating microscope with ultrasonic technique in root canal retreatment,provide a basis for the privention and retreatment of failure of root canal therapy.Methods 98 teeth (142 canals) with initial treatment failure from department of stamtology of Characteristic Medical Center of PAP were chosen from July 2017 to December 2020. And reasons for initial treatment failure were recorded .These canals were treated with ultrasonic technique under dental operating microscope. The success rates were calculated after 6 months.Results 78 teeth were successfully managed with a success rate of 79.6%.The success rates of each category of teeth with initial treatment failure were:92.9%(13/14) for missing root canals;65.4%(17/26)for calcified root canals;75.0%(12/16)for canals blocked by instrument fragments;85.0%(17/20)for canals with perforation.100%(10/10)for canals with open canal system;75.0%(9/12)for ledged canals.Conclusions The use of dental operating microscope with ultrasonic technique is proved effective in root canal retreatment.
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