Effect of Antimicrobial Nanoemulsion on Dental Unit Waterline Biofilm

Introduction: Microbial contamination of dental unit output water caused by biofilm growth in dental unit waterlines (DUWs) is a universal problem with a potentially significant risk of infection to dental staff and patients, particularly those who are medically compromised or immunocompromised. Nanoemulsions are a unique class of disinfectants produced by mixing a water immiscible liquid phase into an aqueous phase under high shear pressure. Nanoemulsions have broad biocidal efficacy against bacteria, enveloped viruses, and fungi by disrupting their outer membranes. Objective: The purpose of the present study was to investigate the efficacy of nanoemulsion against waterline biofilm. Methods: Nanoemulsion composed of 10 vol.% Triton X-100, 25 vol.% soybean oil, 65 vol.% water, and 1 wt.% cetylpyridinium chloride was prepared. Lengths of tubing were obtained from 3 dental unit syringe waterlines. Waterline tubing was exposed to nanoemulsion for 1, 6, 12 and 24 hrs. Levels of bacterial contamination and the effect of nanoemulsion on DWWs biofilm were evaluated by the spread plate method and live-dead staining. Results: Nanoemulsion showed antimicrobial activity against biofilm organisms up to 83.0% within 1 min. After 6 hours of exposure to nanoemulsion no viable count was observed by the spread plate method. Live-dead ratio as determined by confocal microscopy showed similar results. Conclusion: This preliminary study showed that nanoemulsion had effective biofilm activity against biofilm growth in dental unit waterlines and it may be a useful disinfectant to control biofilm organisms. Supported by NIH/NIDCR K08DE018003.