Generation of Hydroxyl Radical from Hydrogen Peroxide by LED Irradiation

Objective: For tooth whitening treatment, hydrogen peroxide (H2O2) is used with visible light or laser irradiation. Usually, high concentration H2O2 has been used for tooth whitening, but if H2O2 leaks onto the oral mucous membrane and periodontal tissues, it will be injured. It is reported that hydroxyl radical (•OH) has the main role in tooth bleaching with H2O2, however, how much •OH is need for bleaching, which wave length is good for the •OH generation were not clarified yet. The aim of this study is to clarify the generation of •OH from H2O2 by 405 or 470nm wave lengths LED irradiation.

Methods: First of all, the generated •OH from 1M H2O2 irradiated with LED (405 or 470nm for 0, 10, 20 or 30s) was measured using electron spin resonance spin-trapping technique. 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) is used as spin-trap agent. Then, each concentration of •OH scavengers, ethanol, dimethyl sulfoxide (DMSO), chelating agent (EDTA), and ascorbic acid (DMPO-OH destroyer) were added to this •OH generation system, respectively.

Results: The amount of •OH (DMPO-OH) was increased by irradiation time of LED light. And, it was in order to 405nm-LED> 470nm-LED > non-irradiated samples. When ethanol or DMSO added to this system, the amount of •OH was decreased and disappeared. Continuously, carbon center radical (•C) was detected. In the case of chelating agent added to this system, the amount of •OH was not changed. When ascorbic acid was added to this system, ascorbic acid radical was detected. Then, these agents added after generated DMPO-OH, the amount of DMPO-OH was not changed by addition of ethanol, DMSO, or EDTA. But, ascorbic acid radical was detected by addition of ascorbic acid.

Conclusion: These results were suggested that the free •OH was generated from H2O2 by LED irradiation.