title: Effects of laser irradiation on tensile strength of bovine dentin.
abstract: 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.
authors.affiliation: Oral Diagnosis and General Dentistry, Dental Hospital, Tokyo Medical and Dental University, Tokyo, Japan. ken1.gend@tmd.ac.jp
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Tonami
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
authors.forename: Junji
authors.initials: J
authors.lastname: Kato
authors.forename: Fumio
authors.initials: F
authors.lastname: Nakano
authors.forename: Fumio
authors.initials: F
authors.lastname: Nishimura
authors.forename: Yuzo
authors.initials: Y
authors.lastname: Takagi
authors.forename: Norimasa
authors.initials: N
authors.lastname: Kurosaki
mesh_terms: 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
chemical_list: D002245:Carbon Dioxide; D015019:Yttrium; D004871:Erbium