title: Detection of Hydroxyl and Perhydroxyl Radical Generation from Bleaching Agents with Nuclear Magnetic Resonance Spectroscopy.
abstract: OBJECTIVE
  Children/adolescent's orodental structures are different in anatomy and physiology from that of adults, therefore require special attention for bleaching with oxidative materials. Hydroxyl radical (OH.) generation from bleaching agents has been considered directly related to both its clinical efficacy and hazardous effect on orodental structures. Nonetheless bleaching agents, indirectly releasing hydrogen peroxide (H2O2), are considered safer yet clinically efficient. Apart from OH., perhydroxyl radicals (HO2.) too, were detected in bleaching chemistry but not yet in dentistry. Therefore, the study aims to detect the OH.and HO2.from bleaching agents with their relative integral value (RIV) using31P nuclear magnetic resonance (31PNMR) spectroscope.
  
  
  METHODS
  Radicals were generated with UV light in 30% H2O2, 35% carbamide peroxide (CP), sodium perborate tetrahydrate (SPT) and; neutral and alkaline 30% H2O2. Radicals were spin-trapped with DIPPMPO in NMR tubes for each test agents as a function of time (0, 1, 2, 3min) at their original pH. Peaks were detected for OH.and HO2.on NMR spectrograph. RIV were read and compared for individual radicals detected.
  
  
  RESULTS
  Only OH.were detected from acidic and neutral bleaching agent (30% acidic and neutral H2O2, 35%CP); both HO2.and OH.from 30% alkaline H2O2; while only HO2.from more alkaline SPT. RIV for OH.was maximum at 1min irradiation of acidic 30%H2O2and 35%CP and minimum at 1min irradiation of neutral 30%H2O2. RIV for HO2.was maximum at 0min irradiation of alkaline 30%H2O2and minimum at 2min irradiation of SPT.
  
  
  CONCLUSIONS
  The bleaching agents having pH- neutral and acidic were always associated with OH.; weak alkaline with both OH.and HO2.; and strong alkaline with HO2.only. It is recommended to check the pH of the bleaching agents and if found acidic, should be made alkaline to minimize oxidative damage to enamel itself and then to pulp/periodontal tissues.
  
  
  BACKGROUND
  H2O2: hydrogen peroxide CP: carbamide peroxide SP: sodium perborate SPT: sodium perborate tetrahydrate ROS: reactive oxygen species31PNMR:31P nuclear magnetic resonance spectroscope RIV: relative integral value OH2.: hydroxyl radical HO2.: perhydroxyl radical O2.: super oxide radical DIPPMPO: 5-(Diisopropoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide DEPMPO: 5-diethoxyphosphoryl-5-methyl-1-pyrroline-n-oxide DMPO: 5,5-dimethyl-1-pyrroline-N-oxide D2O: heavy water EDTA: ethylene diamine tetra acetic acid.
authors.forename: Himanshu
authors.initials: H
authors.lastname: Sharma
authors.forename: Divya S
authors.initials: DS
authors.lastname: Sharma
mesh_terms: D057886:Bleaching Agents / Q000737:chemistry*; D006801:Humans; D017665:Hydroxyl Radical / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D010545:Peroxides / Q000032:analysis*
chemical_list: D057886:Bleaching Agents; D010545:Peroxides; C049375:perhydroxyl radical; D017665:Hydroxyl Radical
keywords: Bleaching; Hydrogen peroxide; Hydroxyl radicals; Perhydroxyl radicals; Reactive oxygen species