Ａｒレーザー照射によるヒトエナメル質への耐酸性付与効果

Abstract

Since Stern et al. (1964) found an incremental effect against acid decalcification of human enamel with an irradiation of ruby laser, many investigations have been carried out with different types of lasers, such as ruby, CO2, and Nd-YAG, for dental caries prevention.Ar laser is widely used in clinics of ophthalmology or plastic surgery. In this experiment, we investigated the possibility of using an Ar laser to increase the acid resistance of human enamel.Significantly less calcium ion was dissolved into lactate buffer solution from the surface of lased enamel than from that of unlased control. Scanning electron microscopy confirmed that an irradiated area of enamel surface was more acid-resistant after acid etching. An energy density of 67 J/cm2 was the optimum intensity for acquirement of acid resistance, as judged from the inhibition of calcium dissolution from the surface zone of irradiated enamel and from scanning electron microscopy of the irradiated area of enamel surface.The application of an absorptive agent to the enamel surface is essential to increasing acid resistance, because the absorption of human enamel for the Ar laser beam is very low. Chinese ink for brush-writing was most effective and waterproof black and red inks, dental plaque disclosing solutoin with red color, and 5% fuchsin solution were also effective.The thickness of enamel from surface to inner part which possessed an acquired acid resistance was calculated by the total amount of calcium ion released from lased enamel into lactate buffer solution. A zone of acid resistance of 144μm was obtained by using black ink and one of 59μm by using red ink.