Advanced Non-Invasive Light Activated Disinfection (ANILAD) technique for endodontic disinfection

Objective: to develop an Advanced Non Invasive Light Activated Disinfection (ANILAD) technique for endodontic disinfection. Method: Methylene blue (MB) dissolved in different formulations; water, 70% glycerol, 70% poly ethylene glycol, and a mixture of glycerol: ethanol: water (MIX), was analyzed for photophysical, photochemical and photobiological characteristics. The antibacterial potential of MB in different formulations activated by visible light of wavelength 664 nm (from a diode laser source with 30mW power) was tested on biofilms of Enterococcus faecalis and Actinomycetes actinomycetemcomitans formed on root canal wall. 72 tooth specimens were used in this study. ANILAD was analyzed for mechanisms of action on bacterial cells. The cytotoxicity and selectivity of ANILAD was compared with sodium hypochlorite under in vitro and ex vivo conditions on fibroblast L929 cells. Result: Aggregation of MB molecules that adversely affected the treatment outcome was significantly higher when MB was dissolved in water (p<0.05). Production of reactive oxygen species (principle antimicrobial agent generated by photoactivation of MB), as indicated from the rates of oxidation of two model substrates were significantly higher in MIX compared to other formulations (p<0.001). MIX based MB formulation effectively penetrated the dentinal tubules. A dual-staged approach of photosensitization using MB dissolved in MIX followed by irradiation in the presence of perfluoro-decahydronaphthalene on four days old biofilms of E. faecalis and A. actinomycetemcomitans on root canal showed 100% and 99.77% killing respectively. The experiments on mechanism of bactericidal activity of ANILAD showed cell membrane dysfunction, and degradation of chromosomal DNA and membrane proteins. The cytotoxicity testing revealed that mammalian cell damage was significantly less in ANILAD compared to sodium hypochlorite (p<0.05). Conclusion: This study indicated the potential application of ANILAD for endodontic disinfection. Acknowledgment: Funding from National University of Singapore (ARF); Grant Number: FY 04 R-224-000-021-101 is gratefully acknowledged.