Objective: To find out whether the frequency of postoperative infectious and inflammatory complications (IC) in subjects treated with placebo (Pl) is greater than those treated with antibiotic (Ab) after extraction of an impacted mandibular third molar (M3). Our hypothesis is there are more IC in Pl than in Ab, with a maximum ratio difference of 0.067.
Study design: A double-blind placebo-controlled randomized clinical trial. The sample was derived from the population of subjects attending Cruces Hospital for evaluation and extraction of 1 M3 under local anesthesia. Patients were treated with postoperative placebo or amoxicillin/clavulanic acid 500/125 mg 3 times a day during 4 days. The outcome variable was infectious and inflammatory complications. Sex, age, smoking, molar depth, angulation, need for sectioning, ostectomy, and operation time were recorded. Analysis was by intention to treat, risk measures, and logistic regression.
Results: In 490 subjects (259 Ab and 231 Pl), the frequency of IC was 1.9% in the Ab and 12.9% in the Pl group (OR 7.6, 95%CI 2.9-19.9; P < .001). The number needed to treat was 10 (7-16). Unadjusted relative risk was 0.15 (0.06-0.38) (P < .001). Absolute reduction risk was 0.11(0.066-0.155)]. Therefore, the hypothesis cannot be rejected. Multivariate analysis shows treatment with antibiotic (OR = 8.66 (3.17-23.67); P < .001) and age (OR = 1.08 (1.00-1.16); P = .029) are the only variables to be included in the logistic regression model.
Conclusion: Amoxicillin/clavulanic acid is efficacious in reducing the incidence of IC following third molar extraction but should not be prescribed in all cases.