CLSM and SEM quantitative analysis of surface topography of human teeth irradiated by Nd:YAG, Er:YAG and CO 2 lasers

Abstract

The quantitative analysis of surface roughness of cavities formed by three different lasers: Nd:YAG (wavelength 1.06 μm), Er:YAG (2.94 μm) and CO 2 laser (10.6 μm) on dentin and enamel surfaces was carried out and compared using confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM). The three types of lasers were applied perpendicularly to the polished surface of human extracted caries-free molars. The highest value of surface roughness (Ra) was observed on enamel and dentin surfaces irradiated by the Er:YAG laser. Cracks were observed on dentin after CO 2 laser irradiation. Er:YAG laser irradiation formed an imbricate-pattern while the Nd:YAG laser had a flake-like surface. A layer of globules representing melted material was observed in the cross-sectional view of dentin irradiated by the Nd:YAG laser. This area had a surface roughness of 0.88 μm, while a smooth area between the globules had Ra of 0.20 μm. Depth profile examination showed deeper cavities on surfaces irradiated by the Er:YAG laser. Quantitative analysis of surface roughness by both CLSM and SEM provided Ra by non-contact method, which was effective to evaluate the structural change of the tooth after laser irradiation.