The Effect of Adjunctive Antimicrobial Photodynamic Therapy in the Treatment of Peri-Implant Diseases: Systematic Review and Meta-Analysis

<b>Background/Objectives</b>: Peri-implant diseases may occur around osseointegrated implants and lead to implant loss. Treatment strategies focus on infection control with decontamination of implant surfaces/pockets. Mechanical debridement (MD) is necessary to reduce biofilm, although it may have limited effects. Antimicrobial photodynamic therapy (aPDT) has been proposed to increase the potential of MD. The aim of this systematic review and meta-analysis is to evaluate aPDT in adjunct to MD versus MD as a single treatment. <b>Methods</b>: An electronic and hand literature search was performed in several databases up to March 2025 to include randomized controlled trials (RCTs). Risk of bias (RoB) was assessed by Cochrane Risk of Bias Tool for RCTs (RoB 2). A meta-analysis was performed with marginal bone level change (MBLc) as the primary outcome, and changes in probing depth (PD) and bleeding on probing (BOP) as secondary outcomes. <b>Results</b>: Eleven RCTs (1056 implants, 878 patients) were included. RoB was high: in 3 studies; some concerns: in 4 studies; low: in 4 studies. The included studies showed a high heterogeneity for MD/aPDT protocols and diagnostic criteria of peri-implant diseases. The meta-analysis revealed, for four studies, a significantly higher MBLc for test patients (M∆: 0.29, 95% CI 0.12, 0.46; <i>p</i> < 0.001) and a significantly higher BOP change (M∆ 5.59; 95% CI: 1.19, 9.86; <i>p</i> = 0.01). No significant difference was found at 6 months in terms of PD change between the test and control groups (M∆ 0.46; 95% CI -0.09, 1.02; <i>p</i> = 0.10). High heterogeneity (I² > 85%) for all three outcomes was found. <b>Conclusions</b>: High heterogeneity, diagnostic variability, and the low number of included studies increase the need of well-designed RCTs on the topic. Despite no conclusive evidence could be found, adjunctive aPDT showed a promising trend to improve MD results.