Adjunctive antibiotics in peri-implantitis surgery reduce bleeding on probing but not other outcomes

AIM: To analyse the effect of systemic amoxicillin and metronidazole on surgical peri-implantitis treatment with a follow-up period of 1 year. MATERIALS AND METHODS: Fifty-nine patients were randomly assigned to receive peri-implantitis surgery supplemented with (29 patients; test) or without (30 patients; control) systemic amoxicillin and metronidazole, in cases with no, one-wall or two-wall bony defects. Primary outcomes were mean peri-implant probing pocket depth (PPD) and mean peri-implant bleeding on probing (BOP); secondary outcomes included disease resolution (composite treatment outcome: residual probing depths ≤ 5 mm; no BOP in one or more probing site; no suppuration on probing), suppuration on probing (SOP) and radiographic marginal bone levels (MBLs), evaluated 3, 6, 9 and 12 months postoperatively (T3, T6, T9, T12). Linear and logistic mixed-effects models were employed. RESULTS: Between-group analyses showed that BOP was significantly lower in the test group compared to the control group at T9 (β = -10.57%, 95% CI: -20.17 to -0.97, p = 0.03) and T12 (β = -14.47%, 95% CI: -25.9 to -3.04, p = 0.01). No other parameters in the mixed-effects models showed statistically significant differences between groups at any timepoint. CONCLUSION: Access-flap peri-implantitis surgery supplemented with systemic amoxicillin and metronidazole led to a statistically significant reduction in peri-implant BOP after 1 year, whereas no other parameters showed statistically significant differences between groups at any timepoint. The clinical implications of these differences should be interpreted with caution, as the isolated short-term effect does not translate into broader or sustained clinical benefit and must be weighed against the risks associated with systemic antibiotic use.