Bactericidal Effect of Antimicrobial Photodynamic Therapy Using Visible Light-responsive Titanium Dioxide -the First Report

Abstract

Background and aim : The aims of the present study were to investigate the relationship between 1 O 2 generated via rutile-TiO 2 and its bactericidal effect on oropathogenic microorganisms, and to evaluate whether antimicrobial photodynamic therapy (a-PDT) via rutile-TiO 2 is applicable to dental treatment. Materials and methods : The experimental groups were defined as follows: only physiological saline without lightemitting diode (LED) irradiation; control group, physiological saline with LED irradiation; LED group, physiological saline including TiO 2 (4 mg/ mL) with LED irradiation; and the photocatalyst (PC) group. The LED irradiation time periods were set to 1, 2 and 3 min. A control group was placed without irradiation at room temperature. Reactive oxygen species and the amount of 1 O 2 generated were measured. A representative bacterial species selected from each oral infectious disease was used for bactericidal testing, including Streptococcus mutans (S. mutans) , Enterococcus faecalis (E. faecalis) , Porphyromonas gingivalis (P. gingivalis) , Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) , and Tannerella forsythia (T. forsythia). The colonyforming units per milliliter (CFU/mL) present after incubation was examined by experimental group, and the relative relationships between the amount of 1 O 2 generated and the various sterilization rates were examined. Results : Whereas S. mutans and E. faecalis were hardly sterilized in all groups, there were remarkable bactericidal effects in the LED group and PC group for A. actinomycetemcomitans, T. forsythia, and P. gingivalis. Conclusion : It appears that, by controlling the amount of 1 O 2 , one can select the bactericidal effect, and theses findings contribute to the development of an evidencebased medicine approach to a-PDT.