Abstract
Objective: The purpose of this study was to investigate the changes of hardness and elastic modulus of human dentin after Nd:YAG laser irradiation. Background Data: The application of Nd:YAG laser in dental hard tissues has been widely studied. However, little information is available about the mechanical properties of teeth after Nd:YAG laser irradiation. Methods: The human dentin was irradiated by Nd:YAG laser through a 400-µm optic bare fiber. The parameters in laser delivery were 100 mJ/pulse - 10 pps - 4 sec and 150 mJ/pulse - 10 pps - 4 sec. Both the hardness and elastic modulus were obtained using an Instron microhardness tester and Vickers indenter. The indentations were then examined under a scanning electron microscope. Results: The hardness and elastic modulus of irradiated human dentin in the energy of 100 mJ/pulse - 10 pps - 4 sec and 150 mJ/pulse - 10 pps - 4 sec were 44.7 kg/mm2 and 22.8 GPa, and 46.9 kg/mm2 and 21.4 GPa, respectively. These values were significantly lower than that of non-irradiated dentin by the Student's t test. Conclusion: Our study demonstrated that Nd:YAG laser irradiation would reduce the hardness and elastic modulus of human dentin.
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