Morphological Study of the Effects of CO2Laser Emitted at 9.3 μm on Human Dentin

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Abstract
The purpose of this study was to investigate the effects of dentin ablation using a carbon dioxide (CO2) laser emitted at 9.3 microm by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). There have been no reports on effects of CO2 laser irradiation emitted at 9.3 microm on dentin by SEM and CLSM. Thirty extracted human teeth showing no clinical signs of caries were used. All teeth were horizontally sectioned to approximately 200 microm thickness and sections were irradiated using a 9.3 microm CO2 laser at different parameters as follows: 26 mJ [energy density (ED) 53.0 J/cm2] and 30 mJ (ED 61.1 J/cm2). After laser irradiation, samples were treated with sodium hypochlorite, stained using rhodamine-123, and observed with CLSM followed by SEM procedures. No craters or cracks were observed, but many small molten and rehardened particles were documented on the sample surface using SEM. Some small cracks were seen in the subsurface layer, and some patent dentinal tubules were detected using CLSM. These results suggest that laser irradiation at these parameters affected the sample surface only (less than 20 microm) and would be less harmful to thermal damage of dental pulp for dentin ablation.