Abstract
We irradiated CO2 laser to bovine enamel at various irradiation power between 1 and 5 W and modes of CW (continuous wave irradiation), SP 1 and SP 2 (pulse irradiation). Crystallographic change in the enamel was examined by using Fourier-transform infrared absorption spectroscopy (FT-IR), X ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The laser irradiation caused a temperature rise at the enamel powder, which was dependent on the laser output and mode. The temperature rise reached about 800℃at an output of 1 W irrespective of the irradiation mode. It was visually confirmed that the enamel powder melted and agglomeration occurred above 1000℃and grain growth of the powder became remarkable with increased temperature up to 1400℃. With the laser irradiation, though the grain growth was not clear, a smooth surface was observed showing the melting of the powder. After an irradiation output of over 3 W, the enamel powder was completely melted irrespective of the irradiation modes. XRD patterns showed apatite in the enamel decomposed to α -tricalcium phosphate (TCP) and tetracalcium phosphate (TTCP) by the laser irradiation. With increasing power output of the laser, the degree of the decomposition increased in all irradiation modes. Apatite almost completely decomposed at the highest output power (5 W) in SP mode.
