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 CO<sub>2</sub> laser is known to be preferable for low invasive treatment of soft tissues and
widely used. The CO<sub>2</sub> 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 CO<sub>2</sub> 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 CO<sub>2</sub>
laser. The violet diode laser could ablate tissue equivalently with the CO<sub>2</sub> laser and coagulate larger area than the CO<sub>2</sub>
laser. Therefore the violet diode laser might be expectable as a surgical tool which has excellent hemostatis.
Several lasers have been used for clinical treatment in dentistry. Among them, diode lasers are attractive because of their compactness compared with other laser sources. Near-infrared diode lasers have been practically used for cutting soft tissues. Because they penetrate deep to soft tissues, they cause sufficiently thick coagulation layer. However, they aren't suitable for removal of carious dentin because absorption by components in dentin is low. Recently, a violet diode laser with a wavelength of 405nm has been developed. It will be effective for cavity preparation because dentin contains about 20% of collagen whose absorption coefficient at a violet wavelength is larger than that at a near-infrared wavelength. In this paper, we examined cutting performance of the violet diode laser for dentin. To our knowledge, there have been no previous reports on application of a violet laser to dentin ablation. Bovine teeth were irradiated by continuous wave violet diode laser with output powers in a range from 0.4W to 2.4W. The beam diameter on the sample was about 270μm and an irradiation time was one second. We obtained the crater ablated at more than an output power of 0.8W. The depth of crater ranged from 20μm at 0.8W to 90μm at 2.4W. Furthermore, the beam spot with an output power of 1.7W was scanned at a speed of 1mm/second corresponding to movement of a dentist's hand in clinical treatment. Grooves with the depth of more than 50μm were also obtained. From these findings, the violet diode laser has good potential for cavity preparation. Therefore, the violet diode laser may become an effective tool for cavity preparation.
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.