title: Passive ultrasonic irrigation in the presence of a low concentration of hydrogen peroxide enhances hydroxyl radical generation and bactericidal effect against Enterococcus faecalis.
abstract: Chemomechanical procedures can be used to eliminate bacteria from root canals. However, detectable bacteria sometimes remain because of the complexity of the root canal system. Endodontic passive ultrasonic irrigation (PUI) with hydrogen peroxide (H2O2) may be a promising option for increasing bactericidal hydroxyl radical (HO•) generation. In this in vitro experiment, we examined the effects of HO• generated using PUI and a low concentration of H2O2. An ultrasonic tip was submerged in 0.45 mol/L (1.5%) H2O2 in a microfuge tube. H2O2 was activated by an ultrasonic unit, the tip of which was kept centered in the tube, to mimic PUI. HO• generation was detected by electron spin resonance spectroscopy. An Enterococcus faecalis suspension in H2O2 was then preparedand activated as described above. Bactericidal effects were assessed by viable counting. Two-way analysis of variance and Tukey's test were used to assess the statistical significance of differences among groups (P < 0.05). HO• generation and bactericidal activity were significantly increased by PUI in H2O2 in a time-dependent manner and were significantly higher than with H2O2 alone or with PUI in a Tris-HCl suspension. These results suggest that PUI in the presence of a low H2O2 concentration is a promising new disinfection strategy.
authors.affiliation: Division of Applied Oral Sciences, Nihon University Graduate School of Dentistry.
authors.forename: Yoshimi
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Hayashi
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Yoshino
authors.forename: Muneaki
authors.initials: M
authors.lastname: Tamura
authors.forename: Ayaka
authors.initials: A
authors.lastname: Yoshida
authors.forename: Haruna
authors.initials: H
authors.lastname: Ibi
authors.forename: Masaichi-Chang-il
authors.initials: MC
authors.lastname: Lee
authors.forename: Kuniyasu
authors.initials: K
authors.lastname: Ochiai
authors.forename: Bunnai
authors.initials: B
authors.lastname: Ogiso
mesh_terms: D004305:Dose-Response Relationship, Drug; D013293:Enterococcus faecalis / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D017665:Hydroxyl Radical / Q000378:metabolism*; D014465:Ultrasonics
chemical_list: D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide