Effect of Ringer’s Lactate versus normal saline irrigation on postoperative morbidity after surgical removal of mandibular impacted third molars: a randomized split-mouth clinical trial

Normal saline remains the most commonly used irrigant during third molar surgery despite evidence that balanced crystalloids may reduce inflammation and acidosis in other surgical fields. This study compared the effect of intraoperative irrigation with lactated Ringer’s solution versus normal saline on postoperative pain, trismus, and facial swelling after bilateral impacted mandibular third molar removal. A prospective, double-blind, split-mouth randomized clinical trial was conducted in 28 healthy patients. Each patient received 10 mL of normal saline on one side and 10 mL of lactated Ringer’s solution on the contralateral side immediately after extraction. Pain (VAS 0–10), maximum mouth opening, and facial swelling (three linear measurements) were assessed on postoperative days 1, 3, 7, and 14. Inter-side differences were compared using the Wilcoxon signed-rank test for pain scores and paired t-tests for mouth opening and facial swelling measurements, with data analysed using SPSS version 27 (IBM Corp., Armonk, NY, USA). Twenty-eight healthy patients completed the study. Pain intensity was significantly lower on the lactated Ringer’s side at all time points (day 1: 4.36 ± 2.71 vs. 6.71 ± 1.59; all P < 0.05), with large effect sizes (r = 0.57–0.69). Maximum mouth opening on day 14 was significantly greater on the lactated Ringer’s side (46.1 ± 7.9 mm vs. 43.3 ± 8.5 mm; P = 0.016; Cohen’s d = 0.744). No significant differences were found in facial swelling at any time point (all P > 0.05). No infections or adverse events occurred. In this small randomized trial, intraoperative irrigation with lactated Ringer’s solution was associated with lower postoperative pain at all assessed time points and improved late trismus recovery compared with normal saline, without differences in swelling. These preliminary findings suggest that lactated Ringer’s may be a promising alternative irrigant for third molar surgery, but larger studies are needed to confirm these effects. This clinical trial was registered in the Iranian Registry of Clinical Trials (IRCT) under the registration number IRCT20130812014333N258. The trial was conducted on July 31, 2025.