Detection of Hydroxyl and Perhydroxyl Radical Generation from Bleaching Agents with Nuclear Magnetic Resonance Spectroscopy.

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 (HO), are considered safer yet clinically efficient. Apart from OH, perhydroxyl radicals (HO) too, were detected in bleaching chemistry but not yet in dentistry. Therefore, the study aims to detect the OH and HO from bleaching agents with their relative integral value (RIV) using P nuclear magnetic resonance (PNMR) spectroscope.

STUDY DESIGN

Radicals were generated with UV light in 30% HO, 35% carbamide peroxide (CP), sodium perborate tetrahydrate (SPT) and; neutral and alkaline 30% HO. 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 HO 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 HO, 35%CP); both HO and OH from 30% alkaline HO; while only HO from more alkaline SPT. RIV for OH was maximum at 1min irradiation of acidic 30%HO and 35%CP and minimum at 1min irradiation of neutral 30%HO. RIV for HOwas maximum at 0min irradiation of alkaline 30%HO and minimum at 2min irradiation of SPT.

CONCLUSION

The bleaching agents having pH- neutral and acidic were always associated with OH; weak alkaline with both OH and HO; and strong alkaline with HO 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.

ABBREVIATIONS

HO: hydrogen peroxide CP: carbamide peroxide SP: sodium perborate SPT: sodium perborate tetrahydrate ROS: reactive oxygen species PNMR: P nuclear magnetic resonance spectroscope RIV: relative integral value OH: hydroxyl radical HO: perhydroxyl radical O: 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 DO: heavy water EDTA: ethylene diamine tetra acetic acid.