Blue Photosensitizer, Red Light, Clear Results: A Review of the Adjunctive Periodontal Treatment with Methylene Blue in Antimicrobial Photodynamic Therapy

Background/Objectives: The standard and effective therapy for treating periodontal disease is scaling and root planing (SRP). However, the adjunctive use of antimicrobial photodynamic therapy (aPDT) has been investigated as a promising approach to enhance periodontal health. This therapy involves the activation of a photosensitizer (PS) through laser, leading to the transfer of energy or electrons to the surrounding environment, ultimately generating reactive oxygen species (ROS). These ROS interact with various intracellular targets, exerting antimicrobial effects. Methylene blue is the most commonly used PS due to its favorable characteristics, including a neutral pH and an absorption peak at 660 nm. The objective of this study was to conduct a literature review to highlight the benefits of methylene blue-mediated aPDT as an adjunct to periodontal treatment. The inclusion criteria were randomized clinical trials that used methylene blue as the PS, published between 2009 and 2024, with a minimum follow-up of three months. Studies included patients with periodontitis treated with SRP alone or in combination with aPDT. Out of 237 initially identified studies with potential for inclusion, 23 met the eligibility criteria and were included in this review. The selected studies were assessed for risk of bias using the Cochrane criteria for randomized trials, in addition to data tabulation and detailed analysis. Although the included studies presented heterogeneous clinical outcomes, an overall improvement in periodontal clinical parameters was observed. The variability in clinical protocols among the studies limited the ability to perform a more homogeneous analysis. Despite these findings supporting the potential role of aPDT as an adjunctive therapy in periodontal treatment, further long-term randomized clinical trials are needed, especially to evaluate its effects across different patient profiles.