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BMC Oral Health. 2019 Jan 11;19(1):10. doi: 10.1186/s12903-018-0694-0.

Molecular damage and responses of oral keratinocyte to hydrogen peroxide.

Author information

1
Department of Biochemistry and Molecular Biology, Pennsylvania State University, State College, Harrisburg, PA, 16803, USA.
2
Department of Stomatology, National Cheng-Kung University Hospital, Tainan, 70101, Taiwan.
3
Graduate Institute of Pharmaceutical Science, Chia-Nan University of Pharmacy and Science, Tainan, 71710, Taiwan.
4
Department of Statistics, National Cheng Kung University, Tainan, 70101, Taiwan.
5
Institute of Oral Medicine and Department of Stomatology, College of Medicine, National Cheng Kung University Hospital, National Cheng Kung University, Tainan, 70101, Taiwan.
6
Department of Stomatology, National Cheng-Kung University Hospital, Tainan, 70101, Taiwan. dbshieh@mail.ncku.edu.tw.
7
Institute of Oral Medicine and Department of Stomatology, College of Medicine, National Cheng Kung University Hospital, National Cheng Kung University, Tainan, 70101, Taiwan. dbshieh@mail.ncku.edu.tw.
8
Center of Applied Nanomedicine, Center for Micro/Nano Science and Technology, Advanced Optronic Technology Center, Innovation Center for Advanced Medical Device Technology, National Cheng Kung University, Tainan, 70101, Taiwan. dbshieh@mail.ncku.edu.tw.
9
Department of Pharmacy, Chia-Nan University of Pharmacy and Science, Tainan, 71710, Taiwan. tzchwa@mail.cnu.edu.tw.

Abstract

BACKGROUND:

Hydrogen peroxide (H2O2)-based tooth bleaching reagents have recently increased in popularity and controversy. H2O2 gel (3%) is used in a Nightguard for vital bleaching; transient tooth sensitivity and oral mucosa irritation have been reported. Genotoxicity and carcinogenicity have also been significant concerns.

METHODS:

We used primary cultured normal human oral keratinocytes (NHOKs) as an in vitro model to investigate the pathological effects to mitochondria functions on human oral keratinocytes exposed to different doses of H2O2 for different durations.

RESULTS:

An MTT assay showed compromised cell viability at a dose over 5 mM. The treatments induced nuclear DNA damage, measured using a single-cell gel electrophoresis assay. A real-time quantitative polymerase chain reaction showed H2O2 induced significant increase in mitochondrial 4977-bp deletion. Mitochondrial membrane potential and apoptosis assays suggested that oxidative damage defense mechanisms were activated after prolonged exposure to H2O2. Reduced intracellular glutathione was an effective defense against oxidative damage from 5 mM of H2O2.

CONCLUSION:

Our study suggests the importance for keratinocyte damage of the dose and the duration of the exposure to H2O2 in at-home-bleaching. A treatment dose ≥100 mM directly causes severe cytotoxicity with as little as 15 min of exposure.

KEYWORDS:

Keratinocyte(s); Molecular genetics; Oxidative stress; Tooth bleaching; Toxicology

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