Effects of laser irradiation on tensile strength of bovine dentin.
OBJECTIVE
The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties.


BACKGROUND
Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues.


METHODS
Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy.


RESULTS
The tensile strengths of the lased dentin and the control group for the Er:YAG, CO2, and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation.


CONCLUSIONS
Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.
Tonami
Ken-Ichi
K
Oral Diagnosis and General Dentistry, Dental Hospital, Tokyo Medical and Dental University, Tokyo, Japan. ken1.gend@tmd.ac.jp
Takahashi
Hidekazu
H
Kato
Junji
J
Nakano
Fumio
F
Nishimura
Fumio
F
Takagi
Yuzo
Y
Kurosaki
Norimasa
N
D000818:Animals; D002245:Carbon Dioxide; D002417:Cattle; D003804:Dentin / Q000502:physiology* / Q000528:radiation effects; D004871:Erbium; D007834:Lasers; D013499:Surface Properties / Q000528:radiation effects; D013718:Tensile Strength / Q000528:radiation effects; D015019:Yttrium
D002245:Carbon Dioxide; D015019:Yttrium; D004871:Erbium