MORPHOLOGICAL AND ATOMIC ANALYTICAL CHANGES AFTER CO2-LASER IRRADIATION EMITTED AT 9.3 MU-M ON HUMAN DENTAL HARD TISSUES

Objective: The purposes of this study were to examine the effects of C O2 laser emitted at 9.3 mu m on human sound and carious dental hard ti ssue ablation with a stereoscope, scanning electron microscope (SEM), and energy dispersive X-ray spectrometer (SEM-EDX) and to identify pos sible applications of this laser in clinical treatment. Summary Backgr ound Data: There has been no report of morphological changes or atomic analytical studies on carious hard tissues after laser irradiation wi th 9.3 mu m CO2 laser, Methods: Sixty extracted human teeth with no ca ries and sixty teeth with enamel or dentin caries were used for this s tudy. All teeth were horizontally sectioned into slices (approximately 3 mm in thickness) and the samples were irradiated with CO2 laser usi ng the following two parameters: a fluence of 78 J/cm(2) and 5 pps or 20 pps for 2 sec. After laser irradiation, half of the samples were ob served by stereoscopy and SEM and the other half were analyzed by SEM- EDX. Results: The lased sound enamel and dentin surfaces showed crater -like structures which had been produced by the high laser energy. On the other hand, some portions of carious hard tissues were evaported b y the laser. A slight amount of carbonization was observed by stereosc opy, Calcium (Ca) and phosphorus (P) content of sound or carious hard tissues was increased significantly (p < 0.01) after laser irradiation , but the ratio of Ca to P after laser irradiation was significantly i ncreased (p < 0.01) on sound hard tissue only. Conclusion: These resul ts suggest that the 9.3 mu m CO2 laser may be useful for the preventio n or removal of caries in clinical situations.