To assess postoperative pain after endodontic therapy and its association with clinical factors such as gender, age, tooth type, pulpal diagnosis, and preoperative pain, length of obturation and sealer extrusion.

The patients, who came to the Clinic of Stomatology, SUMC and received the root canal therapy for molars and premolars from July, 2018 to April, 2019, were randomly selected by simple random sampling (the order of subjects′ recruitment) . There were 140 cases, including 63 males and 77 females. Local Anesthesia (2% Lidocain with 1∶80 000 Epinephrine) was administered. Access cavity was prepared with the help of bur. Canal preparation was completed using standard technique. Access was sealed with sterile dry cotton pellet and restored temporarily with double layer of glass ionomer cement. After one week patients were recalled and access was re-opened, obturation was done using continuous-wave of gutta-percha vertical condensation technique. AH-plus sealer was used. Postoperative radiographs were taken. Patients were recalled after 24 hours and postobturation pain was recorded using visual analogue scale (VAS) . Data was recorded and χ² test and Logistic regression was used for statistical analysis.

A total of 140 cases were included and 84 patients (60%) developed postoperative discomfort. 61 patients (43.6%) reported mild. 9 (6.4%) and 14 (10%) presented moderate and severe pain, respectively. No patients had extremely severe pain. The χ² test showed that postoperative pain was independent of gender and tooth type but correlated with the diagnosis of preoperative pulp infection (χ² = 76.11, P<0.001) and obturation (χ² = 16.3, P<0.001) , as well as the presence of sealer extrusion apical orifice. Multivariate Logistic regression analysis showed that no symptoms before operation and postoperative pain was correspondingly reduced (OR = 0.179, P = 0.048) . If the paste was not exceeded, the incidence of postoperative pain was reduced (OR = 0.039, P = 0.005) . Chronic pulpitis had less postoperative pain than periapical inflammation (OR = 0.034, P<0.001) , while pulp necrosis had more postoperative pain than periapical inflammation (OR = 4.080, P = 0.038) . Compared with overfilling, both adequate filling (OR<0.001, P<0.001) and underfilling<2 mm from the root tip (OR<0.001, P<0.001) reduced postoperative pain.

A significant association of obturation with postoperative pain was observed in this study. Therefore, clinician should avoid the sealer extrusion when doing the obturation. For the patients with pulp neurosis and periapical lesions, communication after root canal treatment should be pay more attention to.