title: Bactericidal effect of hydroxyl radicals generated by the sonolysis and photolysis of hydrogen peroxide for endodontic applications.
abstract: The aim of endodontic root canal treatment is the elimination of bacteria and their products from an infected tooth root canal. To effectively disinfect a root canal, an ultrasonic irrigation system, in which hydroxyl radicals (HO·) generated artificially by sonolysis of H2O2, was developed previously for endodontic applications and was demonstrated to have bactericidal efficacy against Enterococcus faecalis. To improve this system, we examined the in vitro bactericidal effects of HO·generated from H2O2, activated by simultaneous irradiation with ultrasound for sonolysis and dental LED light for photolysis with a peak wavelength of 405 nm. Regarding the LED irradiation, two methods were used: (i) 'ideal' experimental conditions (irradiation close to the glass tube), and (ii) simulated endodontic conditions (more distant irradiation of a masked glass tube). In these conditions, HO·generation from H2O2was detected by electron spin resonance (ESR) spectroscopy, and bactericidal efficacy against E. faecalis was assessed by measuring the colony forming units (CFU)/mL. The results indicated that HO·generation by ESR measurements and the bactericidal effect on E. faecalis by viable count using CFU/mL were enhanced significantly in a time-dependent manner in both conditions. In a comparison of these conditions, bactericidal activity under 'ideal' experimental conditions was similar to that under simulated endodontic conditions. Moreover, the irradiation time for effective killing of E. faecalis through the sonolysis and photolysis of H2O2under simulated endodontic conditions was shorter than that with sonolysis alone. These results demonstrate that H2O2activated by ultrasound and LED light may be a safe and effective disinfection technique for endodontic root canal treatment.
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Haruna
authors.initials: H
authors.lastname: Ibi
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan. Electronic address: hayashi.makoto53@nihon-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Photomedical Dentistry Division, Department of Oral Science, Kanagawa Dental University Graduate School, Kanagawa, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Yoshino
authors.affiliation: Department of Microbiology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Muneaki
authors.initials: M
authors.lastname: Tamura
authors.affiliation: Photomedical Dentistry Division, Department of Oral Science, Kanagawa Dental University Graduate School, Kanagawa, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Yoshida
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Yokosuka-Shonan Disaster Health Emergency Research Center & ESR Laboratories, Graduate School of Dentistry, Kanagawa Dental University, Kanagawa, Japan.
authors.forename: Masaichi-Chang-Il
authors.initials: MC
authors.lastname: Lee
authors.affiliation: Department of Microbiology, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Imai
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Bunnai
authors.initials: B
authors.lastname: Ogiso
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D058491:Bacterial Load; D055117:Curing Lights, Dental; D004203:Disinfection / Q000379:methods; D004708:Endodontics / Q000379:methods; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D017665:Hydroxyl Radical / Q000378:metabolism / Q000494:pharmacology*; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D010782:Photolysis; D000069453:Ultrasonic Waves
chemical_list: D000900:Anti-Bacterial Agents; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide
keywords: Bactericidal activity; Endodontics; Hydrogen peroxide; Hydroxyl radical; Photolysis; Sonolysis