title: Effect of laser therapy on bone tissue submitted to radiotherapy: experimental study in rats.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of laser therapy (lambda = 780 nm) on bone tissue submitted to ionizing radiation.
  
  
  BACKGROUND
  The biostimulation effect of laser in normal bone tissue has already been demonstrated successfully; however its effect on bone tissue submitted to radiotherapy has not yet been studied.
  
  
  METHODS
  Twenty-two Wistar rats were randomly divided into four groups: group I, control (n = 4), submitted only to radiotherapy; group II, laser starting 1 day prior to radiotherapy (n = 6); group III, laser started immediately after radiotherapy (n = 6); group IV, laser 4 weeks after radiotherapy (n = 6). The source of ionizing radiation used was Cobalt 60, which was applied in a single dose of 3000 cGy on the femur. The laser groups received seven applications with a 48-h interval in four points per session of DE = 4 J/cm(2), P = 40 mW, t = 100 sec, and beam diameter of 0.04 cm(2). All animals were killed 6 weeks after radiotherapy.
  
  
  RESULTS
  Clinical examination revealed cutaneous erosions on experimental groups (II, III, and IV) starting at the 6th week after radiotherapy. The radiographic findings showed higher bone density in groups II and IV (p < 0.05) compared to the control group. The results further showed an increase of bone marrow cells, and number of osteocytes and Haversian canals in experimental groups II and IV (p < 0.05). It was also found an increase of osteoblastic activity, in groups II, III, and IV (p < 0.05).
  
  
  CONCLUSIONS
  Laser therapy on bone tissue in rats presented a positive biostimulative effect, especially when applied before or 4 weeks after radiotherapy. However, the use of laser in the parameters above should be used with caution due to epithelial erosions.
authors.affiliation: Federal University of Bahia, Salvador, Bahia, Brazil. samanthadacunha@hotmail.com
authors.forename: Samantha Seara
authors.initials: SS
authors.lastname: Da Cunha
authors.forename: Viviane
authors.initials: V
authors.lastname: Sarmento
authors.forename: Luciana Maria Pedreira
authors.initials: LM
authors.lastname: Ramalho
authors.forename: Darcy
authors.initials: D
authors.lastname: De Almeida
authors.forename: Elaine Bauer
authors.initials: EB
authors.lastname: Veeck
authors.forename: Nilza Pereira
authors.initials: NP
authors.lastname: Da Costa
authors.forename: Alessandra
authors.initials: A
authors.lastname: Mattos
authors.forename: Aparecida Maria
authors.initials: AM
authors.lastname: Marques
authors.forename: Marleny
authors.initials: M
authors.lastname: Gerbi
authors.forename: André Carlos
authors.initials: AC
authors.lastname: Freitas
mesh_terms: D000818:Animals; D001835:Body Weight / Q000528:radiation effects; D001854:Bone Marrow Cells / Q000528:radiation effects; D001842:Bone and Bones / Q000473:pathology / Q000528:radiation effects*; D002452:Cell Count; D006253:Haversian System / Q000528:radiation effects; D028022:Low-Level Light Therapy; D008297:Male; D010011:Osteocytes / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar