title: Morphological changes of bovine mandibular bone irradiated by Er,Cr:YSGG laser: an in vitro study.
abstract: OBJECTIVE
  The purpose of this study was to investigate the morphological changes of bovine mandibular bone following Er,Cr:YSGG laser irradiation in different methods in vitro.
  
  
  BACKGROUND
  Recently, an erbium, chromium/yttrium, scandium, garmet (Er,Cr:YSGG) laser device that emits a laser beam at the wavelength of 2.78 micro m was introduced. This type of infrared laser proved to ablate dental hard tissues effectively. However, the different effects of bone ablation by this laser in different irradiation methods were still unknown.
  
  
  METHODS
  Adult bovine mandibular bones were cut into 24 small pieces, 3-4 cm in length. The parameters of Er,Cr:YSGG laser irradiation were as follows: wavelength was 2.78 micro m, pulse duration was 140-200 micro sec, repetition rate was 20 pulse/sec, power was 4 W, spot size was 1.26 x 10(-3) mm(2), and energy density was 160 J/cm(2). Irradiation methods were different in four groups (six specimens in each group): group A, fixed position and contact mode; group B, fixed position and noncontact mode; group C, nonfixed position and contact mode; and group D, nonfixed position and noncontact mode.
  
  
  RESULTS
  Ablation depth in group A was significantly greater than in group B (p < 0.01). In group A, thermal damage was apparent. In group B, C, and D, thermal damage was minimal.
  
  
  CONCLUSIONS
  Er,Cr:YSGG laser allows for precise surgical bone cutting and ablation with minimal thermal damage to adjacent tissue. Irradiation in different methods may achieve different ablation rates and thermal damage.
authors.affiliation: Department of Endodontics, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Xiaogu
authors.initials: X
authors.lastname: Wang
authors.forename: Nelson Tatsunari
authors.initials: NT
authors.lastname: Ishizaki
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Suzuki
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kimura
authors.forename: Koukichi
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D000818:Animals; D002417:Cattle; D066298:In Vitro Techniques; D007259:Infrared Rays; D007834:Lasers; D008334:Mandible / Q000473:pathology / Q000528:radiation effects* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009336:Necrosis