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Effect of Nd:YAG laser irradiation on the hardness and elastic modulus of human dentin
Bor Shiunn Lee1, Chun Pin Lin, Feng Huei Lin
1Department of Endodontics, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
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-microm 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/mm(2) and 22.8 GPa, and 46.9 kg/mm(2) 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.
