Antimicrobial photodynamic therapy shows negligible clinical improvements for periodontitis compared to conventional treatmentsNew review shows light therapies have limited impact on gum disease

Limitations of conventional disinfectants and rising antimicrobial resistance have accelerated the development of light-based, resistance-free interventions. This mini-review describes the mechanisms and evidence for antimicrobial photodynamic therapy (aPDT), antimicrobial blue light (aBL), antimicrobial selective photothermolysis (aSP) and photothermal therapy (PTT). Unlike antibiotics, light-based interventions avoid inducing microbial resistance or disturbing the host microflora. Interventions were evaluated across endodontics, periodontal and peri-implant disease, oral mucosal infections, and dental caries. Current literature is heavily skewed towards aPDT, leaving other interventions underexplored despite their mechanistic promise. aPDT is currently the only one with systematic reviews and meta-analyses, whereas evidence for aBL and PTT remains confined to in-vitro and preclinical studies. In periodontitis, aPDT achieved statistical significance, but clinical improvements were negligible and below meaningful thresholds, leading official guidelines from major bodies against its routine use. Clinical evidence currently supports aPDT only in oral candidiasis, where outcomes matched conventional treatments. aSP, tested only as pulsed Nd:YAG or CW diode adjuncts to debridement, was not superior to conventional methods, and selectivity has never been measured clinically. Promising directions are aBL, due to its selectivity for periodontopathogens and link to autofluorescence-based diagnosis, and PTT for its combined antimicrobial and regeneration capacity. Physical limiting factors for aPDT and aBL are shallow effective depth and oxygen dependence in anaerobic niches, and a narrow thermal safety margin for aSP and PTT. A recurring gap is lack of translation between microbial reduction and improved clinical outcomes across interventions, highlighting the need for multi-center trials based on clinically proven standardized protocols.