A Study concerning with Removal of Softened Dentin by Nd: YAG Laser Irradiation

Abstract

Many studies describing favorable effects of Nd: YAG Laser irradiation during treatment of hard tissue such as treatment and prevention of dental caries, treatment for hypersensitive dentin, root canal treatment, and root planing, etc., have been reported. Suguro has reported that the effect of removal of softened dentin was influenced strongly by special color mediators. The purpose of this study was to investigate the percent transmittance of various color mediators around wavelength in the near infra-red region and the effect of removal of softened dentin by Nd: YAG Laser irradiation associated with their transmittamce. In this study, 4 color mediators (Indialnk mediators: Black Indialnk, Red Indialnk Waterink mediators: Black Waterink, Blue Waterink) were carried out. Each mediator was diluted to 5, 25, 50 and 75% with distilled water and the degree of transmittamce was measured as a percentage under wavelength range of 800-1300nm. To obtain the softened dentin, bovine mandibular incisors (∅5mm×3mm) were treated with Plank-Rhychlo decalcified solution for 5 days, and stained with above color mediators for 30 minutes. They were then dried in a Vacuum Drying Oven prior to supply to the ablation test. The laser irradiations were carried out 10 seconds with a Nd: YAG laser (CW SLT Contact Laser) with a regulated power-range to 5 watts. The rate of ablation was analyzed by comparing the changes in weight before and after irradiation. Stereoscopic and SEM observation were performed on the irradiated surface of each specimens. The following results were obtained: 1) The percent transmittance of Black Indialnk around a wavelengthin the infra-red region was not detected (0.0%). The percent transmittance of other color mediators were increased by decreasing their density.2) The degree of ablation weight was obtained highest in un diluted solution, and decreased parallel with the diluted of their color mediators. 3) There are correlations between the percent transmittance of color mediators and this ablation in the case of Black Watetlnk, Blue WaterInk, Red Indialnk. 4) In stereoscopic and SEM observation, there were no change on the surface of specimens by Red Indialnk and Blue WaterInk, but it was observed deep defect by Black Indialnk, Black WaterInk. They were observed molten surface like a lava at the bottom of the defect in SEM observation.