| Summary: | 碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 89 === Etching is an important factor for the adhesion of composite resin to enamel. Recently, laser has been used for enamel etching. Enamel surface treated with laser also develop more resistance to acid permeability. Different laser settings result to various alterations. Orthodontic bracket bonding is widely used in today`s dentistry, however white plaque around bracket is still a unfavorable problem. The purpose of this study was to evaluate the morphological changes on intact human enamel surface by Nd:YAG laser irradiation, Er:YAG laser irradiation and phosphoric acid etching. In the first step of our study, intact human enamel was prepared either by laser or acid etching and divided into 5 experimental groups, before the irradiation of Nd:YAG laser, sample were coated with black ink as initiator. Different energy(per pulse), pps, and irradiation time were tested. At the end of each interval, the sample was thoroughly irrigated with water, and imaged under LM. Samples were then compared under SEM. Different etching patterns were found between acid and laser groups under SEM. Acid etching result to smaller microspaces, and Nd:YAG laser produce irregular surface with numerous microcavities, micropores and microfissures. In the Er:YAG group, surface alterations that resemble the acid etching were found. It is concluded that (1) the alteration of enamel morphology was different in the two laser system. (2) 80mJ,10pps and 10secomds(Nd:YAG laser), and 300mJ, 10pps, 10seconds(Er:YAG laser) irradiation produce the significant and precise effect on the modification of human enamel under SEM in our study. (3) Ca/P ratio increased as the energy per pulses elevated in the Nd:YAG laser group.(4) Bonding test indicated that no significant difference exist between laser and acid etching groups.(5) The amounts of microfissures were seldom found on the enamel surface after bonding test in the Nd:YAG laser irradiation group.
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