Effect of Nd:YAG laser irradiation on the hardness and elastic modulus of human dentin.
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
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.


CONCLUSIONS
Our study demonstrated that Nd:YAG laser irradiation would reduce the hardness and elastic modulus of human dentin.
Lee
Bor Shiunn
BS
Department of Endodontics, School of Dentistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
Lin
Chun Pin
CP
Lin
Feng Huei
FH
Li
Uei Ming
UM
Lan
Wan Hong
WH
D003804:Dentin / Q000528:radiation effects*; D004548:Elasticity / Q000528:radiation effects; D006244:Hardness / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D007834:Lasers