The purpose of this study was to evaluate whether a Gallium Nitride (GaN) -based violet laser diode (VLM500) could be used as a light source for light-cured dental resins. Three experimental unfilled resins containing different photoinitiators (camphorquinone, CQ; phenyl propanedione, PPD; or mono acylphosphineoxide, MAPO) were evaluated. These resins were lightcured with a VLM500 laser diode, and their ultimate micro-tensile strengths (μTS) were compared to those cured with three different LED light sources (Curenos, G-Light Prima-normal mode and G-Light Prima-PL mode). The VLM500 produced high µTS values in all three resins, and we concluded that this violet laser diode can be used as a light source for light-cured dental resin materials.

Abstract:The study was conducted to evaluate the surgical performance of a 405-nm diode laser ex vivo. The experiments were carried out using tuna tissue, which was irradiated with a 405-nm diode laser at output powers of 400 mW (694 W/cm 2 ) to 1 W (1735 W/cm 2 ) on a motorized stage moving at a rate of 1 mm/sec. As a control, a 920-nm diode laser was used with the same irradiation conditions. After irradiation, the thickness of ablation and coagulation was measured by stereoscopic microscopy and evaluated statistically. Ablation and coagulation zones were obtained with 405-nm laser irradiation, but not with irradiation at 920 nm. Ablation depth increased significantly with output power and a thick coagulation zone was observed with 405-nm irradiation. The 405-nm diode laser performed well for incising and coagulating soft tissue at a low power density.

Effect of a pulsed electric field (PEF) on polyphenol extraction from grape skins in water was investigated experimentally. The grape skins were immersed in the distilled water between plate-to-plate electrodes in a rectangular shaped reactor. The pulsed voltage was generated by pulse forming network (PFN) to control a pulse width of the high-voltage applied to the plate electrode.The total polyphenol extracted from the grape skins was evaluated as gallic acid using the Folin-Ciocalteu method. The grape skins were observed by a microscopy to clarify the cell morphological change. The experimental results showed the polyphenol extraction from the grape skins was enhanced with increasing pulse width in the PEF treatment. The energy consumption required for the polyphenol extraction decreased with increasing pulse width of the applied voltage. A microscopic measurement clearly showed that many anthocyanoplasts in cells were collapsed and the red color pigments were extracted from anthocyanoplasts into the cell.

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