실활치미백에 대한 Nd-YAG Laser 조사시간의 영향

Abstract

ABSTRACT

The effect of the Nd -YAG Laser irradiation time on non-vital tooth bleaching

Kang, Seung Bok Advisor : Prof. Min, Jeong-Bum Department of Dentistry, Graduate School of Chosun University

The purpose of this in vitro study was to evaluate the effect of the Nd-YAG laser irradiation time on non-vital tooth bleaching. Forty extracted human mandibular premolars with intact crowns were used. After endodontic treatment of these teeth, the canal filling was removed 2mm below the CEJ and covered with a 2mm thick glass-ionomer. The mixture of sodium perborate and 30% hydrogen peroxide were placed in the pulp chamber. The teeth were randomly divided into 4 groups of 10 specimens and Nd-YAG Laser irradiation treatment was performed differently; Group 1 was not irradiated and Group 2, 3, 4 were irradiated for 10, 20, 60 seconds each. Fresh bleaching agent was replaced at every 7 days and then, Nd-YAG Laser was also irradiated. Then, shade change was measured at 7, 14, and 21 days. To evaluate the degree of shade change, 1 evaluator recorded the shade of each teeth using Spectrophotometer (Shadepilot, DeguDent, Inc., Hanau, Germany). To evaluate the effect of Nd-YAG laser irradiation time, obtained shade values were analyzed by two shade matching. The first shade matching was defined as comparison between 2 color values which measured before and 1 week after laser irradiation and the second shade matching was defined as comparison between 2 color values which measured before and right after laser irradiation. In the first shade matching, irradiated teeth showed brighter shade than the non-irradiated teeth. Though group 2 showed the greatest shade change among the groups, the difference between Group 4 was not significant. The results of second shade matching showed that the teeth shade measured right after initial laser irradiation showed statistically significant changes compared to non-irradiated teeth, but there were no differences after 1 week. In conclusion, this study demonstrates that Nd-YAG laser irradiation has influence on the degree of shade change of non-vital bleached teeth.