Tomomi Sudo, DDS (1), Susumu Imai, PhD (2), Tsuyoshi Ochiai, PhD (3,4), Hiroyuki Kanzaki, DDS, PhD (1), Yusuke Morita, DDS (1), Nobuhiro Hanada, DDS, PhD (2), and Yoshiki Nakamura, DDS, PhD (1)
(1) Department of Orthodontics, School of Dental Medicine, Tsurumi University, (2) Department of Translational Research, School of Dental Medicine, Tsurumi University, Yokohama, (3) Photocatalyst Group, Kanagawa Academy of Science and Technology, Kawasaki, and (4) Photocatalysis International Research Center, Tokyo University of Science, Noda, Japan
Purpose: The objectives of this study were to evaluate antibacterial activity of visible light-responsive photocatalytic titanium dioxide (Vis-TiO2) to cariogenic bacteria.
Materials and Methods: In all analyses, brookite Vis-TiO2 was coated on stainless steel surfaces, which were illuminated with visible light (405 nm; LED-generated). Antibacterial activity against cariogenic bacteria was assessed by colony-forming unit (CFU) assay, radial diffusion assay, and bacterial viability analysis.
Results: CFU assay demonstrated that the number of colonies of both bacteria on coated plates with illumination reduced to around 10 %. The coated materials produced clear zones in culture petri dishes of both cariogenic bacterial species. Fluorescence microscopy revealed that most of the bacteria on the coated plates with illumination was identified as dead. In flow cytometry analysis, more than 68% of S. mutans and more than 91% of S. sobrinus were killed on the coated plates with illumination. Vis-TiO2 has strong bactericidal effects on both cariogenic bacteria after illumination. Water-insoluble glucan on the coated plate with illumination was significantly less formed.
Conclusion: The visible light-responsive photocatalytic titanium dioxide coating on orthodontic materials has strong antibacterial activity, which is based primarily on bactericidal activity. The Vis-TiO2 coating is useful for dental caries prevention without any adverse effect to the human body. (Asian Pac J Dent 2016; 16: 15-22.)
Key Words: antibacterial, bactericidal activity, dental caries, orthodontic material photocatalysis, visible light