雷射在牙科醫療應用的研究─雷射照射後牙本質的結構變化(3/3)

ackground and Objective: The purpose of this sudy was to investigate the effects of Nd:YAG laser on human dentine. The compositicnal, structural and phase changes of human dentine after exposed to Nd:YAG laser were examined by X-ray diffractometer (XRD), infrared spectrometer (IR and scanning electron microscopy- Energy dispersive x-ray spectroscopy (SEM-EDX). Study DesignlMaterials and Methods: The study was divided into three parts: 1. the phase transformation and recrystallization of dent;ne after Nd:YAG laser irradiation; 2. the compositional and structural changes of dentine after Nd:YAG laser treatment; 3. the morphoLogy and CaJP ratio changes of dentine after Nd:YAG laser irradiation. Results: After exposed to Nd:YAG laser, there were four peaks belonging to ct-TCP and 3-TCP at 20 = 30.780/34.210 and 32.47¢X/33.Of¢X, respectively. The peaks of cL-TCP and -TCP would gradually increase in intensiy with the elevation of irradiation energy. In IR analysis, two absorption band at 2200 cm1 and 2015 cm¡¦ in the spectrum could be traced on dentine after treated by Nd:YAG laser. The EDX results showed that the molar ratios of calcium (Ca) to phosphorus (P) increased with the elevation of irradiation energy. At the same time, the ratios decreased from the center of crater to the peripheral non-irradiated area. Conclusions: The temperature on the surf ce of dentin after Nd:YAG laser irradiation( 1 5OmJ-3Opps-4sec and 1 5OmJ-2opps-4sec) might be over than 1 5000C. The temperature could lead dentine to be melted, -TCP, j3 -TCP formed and collagen brokendown as well. Thus the laser treatment should be used below the threshold to avoid these by-products