Purpose: The present study was performed to examine the morphological and compositional changes of human dentin after Er,Cr:YSGG laser irradiation in vitro. Materials and Methods: Twenty dentin specimens were prepared and subjected to Er,Cr:YSGG laser irradiation at 3W (33.9 J/cm2) energy density under continuous water spray (1 ml/min). For morphological studies, 5 samples were observed with SEM and 5 with TEM; diamond-knife-cut surfaces of nonirradiated areas were used as control. The remaining 10 samples were subjected to atomic analysis by SEM-EDX. Statistical analysis was performed between lased and unlased areas (control) using the Mann-Whitney U test; a value of p < 0.01 was considered significant. Results: SEM observation revealed a scaly or irregular surface after Er,Cr:YSGG laser irradiation and an absence of smear layer; the orifices of dentinal tubules were exposed. TEM observation of cross sections of lased dentin showed two different zones: the uppermost surface was the ablated zone, containing irregular microparticles, and underneath this layer was an unaffected zone. On the other hand, the diamond-knife-cut surface of dentin showed no microfragment-like structures, and dentinal tubules were also intact. The results of SEM-EDX revealed no significant differences between the Ca:P ratios of lased and unlased areas. Conclusions: Lased dentin surfaces have an etched appearance, but microfragment-like structures are also present which may hamper adhesion of composite restorative materials.
Keywords: Er,Cr:YSGG laser, human dentin, morphological change, compositional change, TEM, SEM, SEM-EDX