Would it really be necessary to use metronidazole as an adjunct in the surgical treatment of periodontitis?

Prospective, parallel, randomized, double-blind, clinical trial. Participants were at least 30 years old, who were systemically healthy, with stages III-IV, grades B-C periodontitis. Of the 50 eligible individuals for the study, 40 were divided into 2 equal groups. The test group received doses of 500 mg of metronidazole, while the control group received a placebo, both administered three times a day for 7 days, commencing immediately after periodontal surgery. All patients were followed up at 3-, 6-, 9-, and 12-months post-surgery. The study utilized probing depth, clinical attachment level, bleeding on probing, and plaque index as parameters for determining the outcomes at each assessment. Microbiological samples were collected for the detection and quantification of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Tannerella forsythia DNA. In order to analyze quantitative variables in a comparison between the test and control groups, Student’s t-tests or Mann-Whitney U tests were utilized. For categorical results, chi-square or Fisher tests were employed. For both probing depth and clinical attachment level, repeated measures ANOVA was used. The statistical significance level was set at p ≤ 0.05. The study found statistically significant differences for probing depth (mean difference, MD = 0.31 mm, 95% confidence interval, CI [0.13; 0.49]; p = 0.001) and clinical attachment level (MD = 0.64 mm, 95% CI [0.02; 1.27]; p = 0.044) only 3 months after surgery, with a reduction observed in the test group. However, despite being statistically significant, these results lack clinical relevance. Although the study found statistically significant results for clinical attachment level (MD = 0.66 mm, 95% CI [0.01; 1.31]; p = 0.045) and probing depth (MD = 0.28 mm, 95% CI [0.09; 0.46]; p = 0.004), these findings do not represent clinically significant gains. Therefore, no evidence was demonstrated to support the use of systemic metronidazole as adjunctive therapy to periodontal surgery.