Effect of sodium percarbonate-containing disinfectant on natural biofilm model of dental unit waterline

Ayuko Takao, PhD (1), Masako Nakano, DDS, PhD (2), Masanori Ikeno, DDS (1), Toshiko Ozawa, DDS, PhD (1), Noriyasu Hosoya, DDS, PhD (2), and Nobuko Maeda, DDS, PhD (1)

(1) Department of Oral Microbiology, and (2) Department of Endodontics Dentistry, School of Dental Medicine, Tsurumi University, Yokohama, Japan

Purpose: Biofilm contamination of dental unit waterlines is an important public health problem. This study evaluated the bactericidal effects of a disinfectant containing sodium percarbonate (Mazak P) against naturally formed biofilms under low corrosion-inducing conditions.
Materials and Methods: Fragments of dental polyurethane tube that retained biofilm were immersed for five minutes into each test solution, and bacterial survival was determined by cultivation of the treated tubes in R2A broth.
Results: The results showed that the bactericidal effects of Mazak P at 10℃ were insufficient and that Stenotrophomonas maltophilia predominantly regrew from the treated fragments. However, when a mixture of Mazak P and benzalkonium chloride (BAC) was used for treatment at 10℃, three of seven treated samples showed no bacterial survival. However, the killing efficacy of this mixture tended to decrease at 25℃, probably because of BAC separation.
Conclusion: All through the experiment, the most resistant strains against disinfection were within the genus Methylobacterium, suggesting that special caution is necessary for red colony-forming opportunistic pathogens.
(Asian Pac J Dent 2016; 16: 29-34.)
Key Words: biofilm, corrosion, dental unit waterline, disinfection, heterotrophic bacteria