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Updated: May 23, 2026

Inactivation of Pathogens via Visible-Light Photolysis of Riboflavin-5′-Phosphate
Published on: April 6, 2022
Bactericidal activity and oral pathogen inactivation by electromagnetic wave irradiation
H Yumoto1, T Tominaga, K Hirao
1Department of Conservative Dentistry, Institute of Health Biosciences, The University of Tokushima Graduate School, 3-18-15 Kuramoto-cho,Tokushima, Japan. yumoto@tokushima-u.ac.jp
Aims:
The aim of this work was to clarify the effects of electromagnetic wave irradiation (EMWI) on oral bacterial pathogens.
Methods And Results:
A Gram-negative (Porphyromonas gingivalis) or Gram-positive (Streptococcus mutans, S. intermedius, Enterococcus faecalis) bacterial suspension was irradiated by EMW apparatus (500-1000 kHz, 5-15 times, 1 s time(-1) ). Quantification of survival bacteria by CFU counting revealed that EMWI exhibited marked bactericidal activity against all tested bacteria and bactericidal activity at 500 kHz increased in an irradiation number-dependent manner. After EMWI at 500 kHz, scanning electron microscopic observations showed that the chain of S. mutans cells was shortened after 5 irradiations and the outlines of bacterial cells (S. mutans and P. gingivalis) were unclear after 5-10 irradiations. EMWI inhibited the inductive effect of S. mutans on pro-inflammatory cytokine production in human monocytes and this inhibitory effect was comparable with that of heat-killed bacteria. Furthermore, using an enzyme activity assay, EMWI partially inactivated the activities of gingipains from P. gingivalis.
Conclusions:
These findings demonstrated that EMWI has inactivation and bactericidal activities against single microbial species among four kinds of oral pathogens.
Significance And Impact Of The Study:
Electromagnetic wave irradiation may be applicable for medical disinfection and sterilization, such as refractory periapical periodontitis.
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