Abstract:

Objective To analyse the causes of failure in root canal treatment, evaluate the clinical effect of micro-ultrasonic technique on root canal retreatment, and explore the method to improve the success rate of retreatment. Methods A total of 63 patients (82 teeth) who failed in first root canal treatment were selected, and the causes of failure were analysed. Micro-ultrasonic technique was used to clean and expand the root canal, and warm vertical technique was employed to fill the root canal. Patients were reexamined 3, 6, 12 and 24 months after treatment, and the success rate of root canal retreatment was calculated. The influencing factors for clinical effect of root canal retreatment were explored with literature review. Results Iatrogenic factors (underfilling, loose filling, root canal missing and broken instrument in root canal) contributed to most (67.07%) of the failure in first root canal retreatment. After 2 years of follow up, the success rate of retreatment was 86.59%, including cure in 48 teeth, improvement in 23 teeth and failure in 11 teeth. Among the 11 teeth with failure in retreatment, 3 were extracted due to tooth fracture or vertical root fracture, and the other 8 exhibited fine root canal filling and enlarged apical shadow on X-ray images or had mucosa swelling and sinus. Conclusion Iatrogenic factors are the major causes for failure in root canal treatment. The success rate of root canal retreatment can be increased by proper management with micro-ultrasonic technique and warm vertical technique.

Key words: root canal retreatment, dental operating microscope, ultrasonic technique, warm vertical obturation