RESUMEN
AIM: This randomized, prospective, controlled trial assessed the effect of occlusal reduction on post-treatment endodontic pain and medication intake following root canal treatment of mandibular posterior teeth with symptomatic irreversible pulpitis with sensitivity to percussion treated in two visits. METHODOLOGY: Three hundred and eight patients were randomly assigned into two equal groups according to whether occlusal reduction was done or not (n = 154). For all patients, root canal treatment was carried out in two visits without intracanal medication. Patients assessed their pain using the 0-10 numerical rating scale (NRS) 6, 12, 24 and 48 h after the first visit (post-instrumentation) and 6 and 12 h following root canal filling (post-obturation). Patients, also, recorded their medication intake (sham or analgesic), post-instrumentation and post-obturation; patients initially received a sham capsule, but, if pain persisted, an analgesic was prescribed. Data were analysed using Mann-Whitney U-test, Friedman's test, Wilcoxon's rank test and chi-square (χ2 ) test. The relative risk (RR) and its 95% confidence interval (CI) were calculated for binary data. RESULTS: Occlusal reduction was associated with lower pain intensity than no occlusal reduction at 12 and 24 h post-instrumentation (P < 0.05). Pain intensity significantly and gradually decreased with both groups at all post-instrumentation and post-obturation time-points compared to preoperative pain (P < 0.05). The RR of moderate-to-severe pain was 0.61 (95% CI: 0.41, 0.91) 12 h post-instrumentation, and the RR of pain incidence, regardless of its level, was 0.75 (95% CI: 0.61, 0.92) 24 h post-instrumentation. There was no significant difference in medication intake (sham or analgesic) between groups (P > 0.05). CONCLUSIONS: Occlusal reduction was effective in reducing the intensity of postoperative pain 12 h and 24 h after root canal instrumentation in the first visit in patients with symptomatic irreversible pulpitis with sensitivity to percussion. Occlusal reduction lowered the risk of moderate-to-severe pain by about 40% 12 h post-instrumentation and the overall risk of pain by 25% 24 h post-instrumentation; yet, it did not affect medication intake.