Retrospective evaluation of the factors affecting success in retreatment

The purpose of this study is to assess the factors that may contribute to the failure of primary root canal treatment and to evaluate the impact of prognostic factors believed to be effective in the success of retreatment on the treatment outcomes in terms of tooth survival and complete healing. The initial radiographs of 541 root canal-treated teeth of 423 patients who presented to the Endodontics Clinic of Başkent University Faculty of Dentistry between April 2013 and January 2021 and whose root canal treatment was renewed by a experienced single endodontist, and the results of clinical and radiographic evaluations performed at least 6 months after retreatment were retrospectively analyzed. The study included 240 teeth from 181 patients (64.1% (116) female, 35.9% (65) male, mean age 43±13 years) who met the inclusion criteria. The periapical status and clinical findings of the teeth included in the study were investigated at initial and follow-up appointments. Two independent researchers evaluated periapical condition according to the Periapical Index (PAI) scoring system. It was observed that complete healing occurred in 92.1% of the teeth undergoing retreatment, while 6.3% showed ongoing healing, and 1.7% did not exhibit any improvement. Factors evaluated in teeth undergoing retreatment, including gender, presence of systemic disease, tooth type, number of canals, presence of preoperative symptoms, presence of undetected canals in previous treatment, preparation technique, number of sessions, type of postoperative restoration, and age, did not show a significant impact on complete healing (p>0.05). When complete healing rates were compared according to the type of restoration applied after primary root canal treatment, teeth with composite restoration after primary root canal treatment showed a significantly lower success rate (14.8%) after retreatment compared to other restoration types (p<0.05). When the relationship between the quality of the previous root canal filling and complete healing after retreatment was analyzed, it was found that 3 (60%) of the 5 teeth with overfilling root canals did not achieve complete healing and the percentage of complete healing in this group was statistically significantly lower than in the other groups (p<0.05). A significant relationship was found between the presence and size of preoperative lesions and complete healing in retreated teeth (p<0.001). The percentage of complete healing was found to be 96.3% in those with PAI 3, 80.6% in those with PAI 4, and 66.7% in those with PAI 5. While complete healing was observed in 92.1% of the teeth, ongoing healing was present in 6.3%, and no improvement was noted in 1.7%. The survival rate of teeth after retreatment was found to be 98.4%. In conclusion this study shows that; The success of retreatment may be affected by the over canal filling in the primary treatment, the presence and size of periapical lesions, and the type of preoperative restoration.