Degradation of Candida Biofilms On PMMA By 405-nm LED Light

Objectives: This study aimed to investigate the degradation effects of irradiation of 405-nm light-emitting diode (LED) light on biofilms of Candida albicans (C. albicans) and Candida glabrata (C. glabrata) formed on denture-base resin, and the influences of irradiation on mechanical and surface characters of the resin.
Methods: Discs (10 mm in diameter, 2 mm in thickness) of polymethyl methacrylate (PMMA) denture-base resin were prepared and the biofilm of C. albicans or C. glabrata was formed on the discs. The discs with each Candida biofilm were irradiated with 405-nm LED light under a constant output power of 280 mW/cm² for a variety of periods in a moisture chamber at 100 % relative humidity. After the irradiation, each Candida biofilm on disks was analyzed using colony forming unit (CFU) assay, fluorescence microscopy and scanning electron microscopy (SEM). Rectangular parallelepiped specimens (64 mm x 10 mm x 3.3 mm) of PMMA denture-base resin were prepared, and their changes in flexural strength (FS), flexural modulus (FM) and surface roughness before and after irradiation with 405-nm LED light were also evaluated.
Results: The irradiation for 30 min fully inhibited the colony formation of both Candida species, and fluorescence microscopy showed that almost every Candida cell was dead after irradiation. SEM showed various cell damage patterns of both irradiated Candida species, such as wrinkle, shrinkage and the cell surface damage. Although the increasing tendency was noted in FS after irradiation, no significant changes in FM or surface roughness were not observed before and after irradiation.
Conclusions: The irradiation with 405-nm LED light induced the degradation of the biofilms of C. albicans and C. glabrata on denture-base resin even in the absence of photosensitizers without any deteriorations of the resin.