Effects of 275 nm Ultraviolet Light-Emitting Diode Irradiation on Oral Bacteria In Vitro and Toothbrush Sanitization

The oral cavity harbors a complex microbial community where pathogens implicated in dental caries and periodontitis can heavily colonize toothbrushes, transforming them into persistent sources of contamination that threaten both oral and systemic health. Consequently, this study evaluated the bactericidal efficacy of 275 nm ultraviolet light-emitting diode (UV-LED) irradiation against common oral bacteria in vitro and its practical utility for extraoral toothbrush sanitization. Suspensions of Streptococcus mutans, Streptococcus sanguinis, Porphyromonas gingivalis, and Fusobacterium nucleatum were irradiated for 3 min, 6 min, and 9 min. Bacterial growth and bactericidal effects were measured using growth curve and colony-forming unit assays, respectively. LIVE/DEAD staining and crystal violet staining were used to evaluate the bacterial viability and multispecies biofilm formation after irradiation. Additionally, the sanitization effects of a 275 nm UVC-based portable device on used toothbrushes were investigated. Direct UVC irradiation at 275 nm exhibited strong bactericidal effects against common oral bacteria in vitro. UVC irradiation also showed great sanitization effects on used toothbrushes. In summary, the vulnerability of common oral bacteria to 275 nm UVC, combined with its sanitizing efficacy on used toothbrushes, establishes a solid basis for extraoral sanitization, offering a reliable strategy to mitigate the risk of oral pathogen transmission from contaminated toothbrushes.