This retrospective cohort study examined the incidence of interappointment emergencies during multiple-visit molar root canal treatments conducted by undergraduate students. Treatments performed without the use of intracanal medicament were compared to treatments that incorporated calcium hydroxide as an intracanal medicament.

Interappointment emergencies, defined as instances of pain or swelling that required the patient to make an unscheduled follow-up visit, were recorded for up to 2 months after the intervention. To avoid the influence of obturation on the observed incidence of emergency visits, only unscheduled visits occurring between the start and end of the root canal treatment were included.

Of the 719 patients included in this study, 77 (10.7%) were recorded as experiencing interappointment emergencies. Of these emergencies, 62% occurred within 2 weeks following the most recent intervention. In the group of patients who did not receive intracanal medicament, the incidence of interappointment emergencies was 11.9% (46 of 385 patients). In comparison, this rate was 9.3% (31 of 334 patients) among those who received calcium hydroxide as an intracanal medicament (odds ratio, 1.33; 95% confidence interval, 0.82–2.15; p = 0.249).

Interappointment emergencies may arise at any point during root canal treatment, but they most commonly occur within the first 2 weeks following intervention. The omission of intracanal medicament in multiple-visit molar root canal treatments, performed by undergraduate students, did not significantly increase the incidence of these emergencies.

This study aimed to assess prospectively the clinical outcome of nonsurgical endodontic treatment and identify patient- and tooth-related factors, rather than treatment-related factors, that were the best predictors of this outcome.

The inception cohort comprised 441 teeth (320 patients) and 175 teeth (123 patients) were followed up for 1-2 years. Age, gender, presence of medical disease, number of canals, previous endodontic treatment, presence of sensitivity and pain, pulp vitality, swelling or sinus tract of pulpal origin on the gingiva, periapical radiolucency and tendency of unilateral bite on the affected tooth were recorded at treatment start.

The outcome was classified on the basis of periapical radiolucency as healed or non healed. The overall healed rate in these cases, including nonsurgical retreatment, was 81.1%. Four tooth-related factors had a negative impact in the bivariate analysis: previous endodontic treatment, necrotic pulp, preoperative gingival swelling or sinus tract of pulpal origin, and preoperative periapical radiolucency. Stepwise logistic regression analysis including patient-, tooth-related factors and level of the root canal filling as a treatment-related factor showed that preoperative gingival lesion (odds ratio [OR]: 4.4; p = 0.005), preoperative periapical radiolucency (OR: 3.6; p = 0.011), and ≤ 1-2 mm under root filling length (OR: 9.6; p = 0.012) were significant predictors of failure.

A preoperative gingival lesion of pulpal origin can influence the outcome of nonsurgical endodontic treatment in addition to preoperative periapical radiolucency.