Taking antibiotics may provide clinical benefits beyond those normally achieved with just scaling and root planing (SRP), but there may be even more to it, according to a study published recently in the Journal of Periodontology.
The timing of the course of antibiotics -- taking them sooner versus later -- may be what really makes the difference, the authors wrote.
“Starting antibiotics at the beginning of treatment may help to establish a healthier, more stable bacterial community in the gums, potentially offering better long-term protection against disease recurrence,” wrote the authors, led by Dr. Magda Feres of the Harvard School of Dental Medicine in Boston (J Periodontol, February 7, 2026).
To establish whether the timing of antibiotics administration, relative to SRP, affects the clinical and microbiological outcomes of treatment for gum disease, a double-blind, placebo-controlled, randomized clinical trial was conducted with 68 patients with stage III/IV periodontitis. The patients were assigned to receive SRP over two weeks with either metronidazole or amoxicillin three times a day during SRP. Some were given antibiotics during SRP, and some were administered immediately after, according to the study.
Clinical parameters, clinical attachment level, visible plaque, bleeding on probing, suppuration were taken at baseline, three months, and one year. Subgingival biofilm samples were taken from each patient and analyzed.
After one year, those in the early and later antibiotics groups showed similar improvements in gum health, and more than half achieved successful treatment outcomes. About 60% of patients in each group reached the primary treatment outcome (≤ four sites with a probing depth of ≥ 5 mm at one year; p > 0.05), and the reductions in probing depth and clinical attachment levels did not differ dramatically between the groups (p > 0.05), the authors wrote.
However, patients who started antibiotics early had quicker and more thorough changes in their oral bacteria. The bad germs disappeared more quickly while the good bacteria created a stable, protective atmosphere sooner, they wrote.
Nevertheless, the study had limitations, including a lack of greater insight into microbial activity, the authors wrote.
In the future, studies should be completed to include longitudinal and functional analyses to assess the long-term effect of antibiotic timing as it relates to gum disease outcomes, they wrote.
“Initiating antibiotic therapy early may support a more favorable trajectory of microbial rebiosis, contributing to the establishment of a more stable, health-associated subgingival community over time,” Feres and colleagues wrote.
