Study on the Ablation Efficacy of Er:YAG Laser on Human Dentin

• Main Authors: YU-LIN , HUNG, 洪余林
• Other Authors: 藍萬烘
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/87792392140690066892

碩士 === 國立臺灣大學 === 臨床牙醫學研究所 === 90 === Er:YAG lasers are the most popular solid lasers for dental clinic now. They produce much less vibration, noise and pain. However, they would cause harmful effects on the dentin surface when used under improper energy. The purpose of this study was to investigate the ablation efficacy of Er:YAG laser on human dentin. Moreover, we also evaluated the morphological compositional and phase changes of dentin surface after irradiation by different laser energy. Twenty five dentin specimens were used in part (I) of the study. After being ground, dentin surface was divided into four areas and were randomly divided into nine groups for subsequent different parameters of laser irradiation. Groups one to nine were irradiated by Er:YAG laser from 10J to 50J. The laser handpiece was mounted to make the tip perpendicular and 1 mm away from the dentinal surface. The specimen was then subjected to laser treatment for 10 seconds. All specimens in part (I) of the study were examined by scanning electron microscope(SEM) with the depth of each specimen evaluated. The aims of the part (II) of the study focus on the morphological changes of dentin surface after exposure to Er:YAG laser. The aims of the part (III) of the study consist of the evaluation of the compositional and phase changes of dentin surface under different energy of laser irradiation. The results revealed the depth of group (1) to group (9) as followed : (1):61.37(±9.29) μm、(2):231.28(±57.7) μm、(3):419.94(±121.76) μm、(4):578.39(±63.64) μm、(5):752.31(±115.23) μm、(6):930.36(±105.57) μm、(7):988.7(±32.46) μm、(8):1199.7(±69.7) μm、(9):1275.64(±90.89) μm . On laser-treated dentin, flaky, scaly, and rough surfaces were seen. The surfaces were clean with several morphological reliefs, which indicated that ER:YAG laser could selectively ablate the dentin structures. Crack lines and charring were shown on the samples of pulse energy over 350mJ group. Denti showed four peaks on the X-ray diffractometer corresponding to α- tricalcium phosphate (TCP) and β-TCP at 2θ=30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. In Fourier transforming infrared analysis, two absorption bands at 2200 cm-1and 2015 could be found on dentin treated by Er:YAG laser without water spray cooling. The results revealed the harmful effect on the dentin surface under powerful energy. Hence (in conclusion), we suggest the irradiation energy parameter of Er:YAG laser with water spray cooling that is the most appropriate for ablating the dentin is 300mJ/pulse- 10 pps-10 s.