title: Bactericidal effect of hydroxyl radicals generated from a low concentration hydrogen peroxide with ultrasound in endodontic treatment.
abstract: One approach to enhance the disinfection of root canals in endodontic treatment is ultrasonic irrigation with sodium hypochlorite. Reactive oxygen species, such as hydroxyl radical, are generated by biological defense systems to kill invading bacteria. Ultrasonic irrigation with hydrogen peroxide may be a promising option to increase hydroxyl radical generation. We examined the bactericidal effects of hydroxyl radical generated from low concentration hydrogen peroxide with ultrasound in vitro. An ultrasonic tip was submerged in 0.5 or 1.0 M hydrogen peroxide in a microfuge tube. hydrogen peroxide was irradiated with the ultrasound, the tip of which was maintained centered in the tube to mimic ultrasonic irrigation. Hydroxyl radical generation was assessed by electron spin resonance spectroscopy. Subsequently, Enterococcus faecalis suspension in hydrogen peroxide was prepared and irradiated as described above. Bactericidal effects were assessed by viable counting. Electron spin resonance measurements showed that hydroxyl radical generation increased significantly in a time- and dose-dependent manner (two-way analysis of variance and Tukey's test, p<0.05). Moreover, the bactericidal effects of hydrogen peroxide against Enterococcus faecalis were enhanced by ultrasonic irradiation in a time- and dose-dependent manner. These results suggest that ultrasonic irrigation in the presence of low concentration hydrogen peroxide can serve as a disinfection strategy in endodontic treatment.
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.affiliation: Photomedical Dentistry, Department of Oral Science Graduate School of Kanagawa Dental University, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Yoshino
authors.affiliation: Department of Microbiology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Muneaki
authors.initials: M
authors.lastname: Tamura
authors.affiliation: Photomedical Dentistry, Department of Oral Science Graduate School of Kanagawa Dental University, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Yoshida
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Haruna
authors.initials: H
authors.lastname: Ibi
authors.affiliation: Yokosuka-Shonan Disaster Health Emergency Research Center & ESR Laboratories, Kanagawa Dental University, 82 Inaoka-cho, Yokosuka, Kanagawa 238-8580, Japan.
authors.forename: Masaichi-Chang-Il
authors.initials: MC
authors.lastname: Lee
authors.affiliation: Department of Microbiology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Kuniyasu
authors.initials: K
authors.lastname: Ochiai
authors.affiliation: Department of Endodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan.
authors.forename: Bunnai
authors.initials: B
authors.lastname: Ogiso
keywords: bactericidal effect; electron spin resonance; hydrogen peroxide; hydroxyl radical; ultrasound