Additional root canal enlargement increases immediate postoperative pain: a randomized controlled trial.

This prospective, double-blind, randomized clinical trial aimed to evaluate the effect of an additional instrument following the single-file instrumentation approach on postoperative pain. Fifty-six mandibular molars with asymptomatic apical periodontitis were randomly assigned to two groups: G1 - instrumentation using a single reciprocating file; G2 - additional enlargement. The frequency and intensity of postoperative pain were assessed at 24 h, 48 h, and 7 days after endodontic treatment using the numerical pain assessment scale (NPAS) (Mann-Whitney U test). Analgesic intake was also recorded and analyzed using chi-square or Fisher's exact tests. The incidence of root canal filling extrusion was also evaluated (chi-square). Statistical significance was set at p < 0.05. At 24 h, the incidence of postoperative pain was higher when additional enlargement was performed (p = 0.019). The incidence of pain was similar between groups after 48 h (p = 0.121) and 7 days (p = 1.000). The intensity of pain was also higher at 24 h in Group 2 (p = 0.019), while it was similar between groups after 48 h (p = 0.177) and 7 days (p = 1.000). The frequency of analgesic intake was higher in Group 2 after 24 h (p = 0.019). The incidence of root canal filling material extrusion was similar in both groups (p = 0.181). In conclusion, additional enlargement following single-file root canal preparation resulted in a higher incidence and intensity of postoperative pain immediately after treatment (24 h), with no significant impact at 48 h and 7 days.