Abstract
Laser irradiation has been widely used in dental clinics for cutting and evaporating hard tissue. However, there are only a few studies on the crystallographic change of the enamel caused by the heat evolved during laser irradiation. We investigated the crystallographic change of bovine enamel powder by CO2 laser irradiation at various energy levels using Fourier-transform infrared absorption spectroscopy (FT-IR), X-ray diffraction(XRD) and scanning electron microscopy(SEM). We also performed thermo gravimetric analysis (TG) of enamel powder.
The following results were obtained;
1. Average temperature rises were estimated at 800℃ or more, 1000℃, 1200℃ and 1400℃ or more when the CO2 laser was irradiated at 1W, 3W, 5W and 7W of output levels, respectively. However, the maximum temperature was probably even higher around the focus point of the irradiation area at each output level.
2. HAP of the bovine enamel seemed to be completely melted over 3W of the laser output level and α-TCP and TTCP re-crystallized during cooling after the irradiation.
3. SEM observation clearly showed spherical particles of various sizes, which were formed by the melting of bovine enamel during the laser irradiation. The surface of the spherical particles become smoother at the higher output level over 5W.
