Go Akashi

The amounts of hydroxyl radicals generated by titanium dioxide and 3.5% hydrogen peroxide under 405-nm diode laser irradiation

A new bleaching agent consisting of a titanium dioxide photocatalyst and 3.5% hydrogen peroxide has recently been developed for in-office bleaching and has proven to react well with irradiated light around a wavelength of 400 nm. This study was conducted to evaluate the efficacy of dental bleaching with a 405-nm diode laser irradiation on titanium dioxide and 3.5% hydrogen peroxide by measuring the generation of hydroxyl radicals. The amount of hydroxyl radicals generated from a titanium dioxide and 3.5% hydrogen peroxide irradiated by a 405-nm diode laser were measured using electron spin resonance spin-trapping techniques. The irradiation conditions of the laser were a spot size of 1 mm, output powers of 100, 200, 400 mW, and 600 mW, and irradiation times of 10, 20, 30, and 60 s. Nonirradiated samples were used as controls. DMPO-OH adduct spectra and DMPO-O2− adduct spectra were observed when the bleaching agent was irradiated by laser light. The amount of hydroxyl radicals generated changed in accordance with adjustments in the irradiation power and irradiation time. In the nonirradiated controls, hydroxyl radicals were generated in far smaller amounts. The 405-nm diode laser is effective in inducing the generation of hydroxyl radicals and shows promise as a bleaching light source for use in combination with bleaching agents composed of titanium dioxide and low concentrations of hydrogen peroxide.

Effects on soft tissue produced by a visible violet diode laser

A violet laser with an oscillating wavelength of 405 nm has recently been developed in industry. Laser irradiation at this wavelength penetrates tissue less aggressively than Nd:YAG and diode laser irradiation at wavelengths of 810 nm, and more aggressively than irradiation by carbon dioxide laser. Further, protein is reported to absorb this 405 nm wavelength at high rates. This study was conducted to evaluate the effect of the violet laser on soft tissue in vitro. A prototype violet diode laser produced by Sumitomo Electric Industries was used. This laser irradiates with a continuous wave at a wavelength of 405 nm. Soft tissue samples were irradiated by the device at output powers in a range from 850 mW to 2400 mW as the irradiated samples were conveyed at a scanning speed of 1 mm/sec. The beam diameter was about 270 μm. The irradiated samples were observed by a stereoscopic microscope, fixed with a 10% neutral formalin aqueous solution, and histologically examined. Irradiation by the device vaporized a U-shaped section of tissue to a depth of about 350 to 900 μm. A denatured layer measuring 300 to 450 μm in width was observed under the carbonization layer. The depth of vaporization increased in proportion to the power. These results indicate that a violet laser has good potential to become an effective laser for the cutting and coagulation of soft tissue.

Comparison of violet diode laser with CO 2 laser in surgical performance of soft tissues

The violet diode laser (405nm) has recently begun to be studied for surgical use and authors reported the soft tissue could be effectively incised by irradiation power of even less than 1W. The wavelength of this laser is highly absorbed by hemoglobin, myoglobin or melanin pigment. Cutting or ablating soft tissues by lower irradiation power might be preferable for wound healing. The CO2 laser is known to be preferable for low invasive treatment of soft tissues and widely used. The CO2 laser light (10.6μm) is highly absorbed by water and proper for effective ablation of soft tissues. In this paper, we report the comparison of the violet diode laser with the CO2 laser in surgical performance of soft tissues. Tuna tissue was used as an experimental sample. In the case of the violet diode laser, extensive vaporization of tissue was observed after the expansion of coagulation. Carbonization of tissue was observed after the explosion. On the other hand, consecutive vaporization and carbonization were observed immediately after irradiation in the case of CO2 laser. The violet diode laser could ablate tissue equivalently with the CO2 laser and coagulate larger area than the CO2 laser. Therefore the violet diode laser might be expectable as a surgical tool which has excellent hemostatis.