[A five-year experience for treating patients with chronic apical periodontitis with root canal treatment: a retrospective cohort study].

PURPOSE To investigate the clinical outcomes, including survival and periapical healing rates and failure causes, of root canal treatment for patients with periapical lesion. METHODS A retrospective cohort study was conducted which enrolled patients admitted for the evaluation and management of periapical lesion with root canal treatment. The primary predictor variables were difficulty assessment of root canal therapy (DARCT),which was divided into lower（DARCT =3-4）, medium (DARCT =5-7) and higher (DARCT =8-9) difficulty root canal, in terms of canal length, curvature and calcification. The primary outcome measurement was the incidence of periapical healing and survival rate. Potential confounders included patient demographics, canal number, root canal filling, and coronal restoration. SPSS 21.0 software package was used for data analysis. RESULTS The 5-year survival rate was 81.4%(83/102) and healing rate was 77.1% (64/83). DARCT was significantly associated with the survival rate(P=0.017). Root fracture, deep pockets lesions and periodontal abscess were observed in DARCT with a value of 8-9(P=0.027), leading to tooth extraction. The teeth with multiple root canals were extracted due to recurrent or persistent periapical lesion (P=0.004). Chi-square test showed that root canal number (P=0.021), quality of root canal filling (P=0.006) as well as DARCT (P=0.000) were significantly correlated with the final healing rate. Multivariate logistic regression analysis showed that DARCT (P=0.000) and the quality of root canal filling (P=0.033) were associated with the final healing rate. CONCLUSIONS DARCT and the quality of root canal filling play key roles in the clinical prognosis of periapical lesion, DARCT and number of root canal are more likely to be correlated with failure.