title: Photoengineering of bone repair processes.
abstract: OBJECTIVE
  This paper aims to report the state of the art with respect to photoengineering of bone repair using laser therapy.
  
  
  BACKGROUND
  Laser therapy has been reported as an important tool to positively stimulate bone both in vivo and in vitro. These results indicate that photophysical and photochemical properties of some wavelengths are primarily responsible for the tissue responses. The use of correct and appropriate parameters has been shown to be effective in the promotion of a positive biomodulative effect in healing bone.
  
  
  METHODS
  A series of papers reporting the effects of laser therapy on bone cells and tissue are presented, and new and promising protocols developed by our group are presented.
  
  
  RESULTS
  The results of our studies and others indicate that bone irradiated mostly with infrared (IR) wavelengths shows increased osteoblastic proliferation, collagen deposition, and bone neorformation when compared to nonirradiated bone. Further, the effect of laser therapy is more effective if the treatment is carried out at early stages when high cellular proliferation occurs. Vascular responses to laser therapy were also suggested as one of the possible mechanisms responsible for the positive clinical results observed following laser therapy. It still remains uncertain if bone stimulation by laser light is a general effect or if the isolate stimulation of osteoblasts is possible.
  
  
  CONCLUSIONS
  It is possible that the laser therapy effect on bone regeneration depends not only on the total dose of irradiation, but also on the irradiation time and the irradiation mode. The threshold parameter energy density and intensity are biologically independent of one another. This independence accounts for the success and the failure of laser therapy achieved at low-energy density levels.
authors.affiliation: Laser Center, School of Dentistry, Department of Propedêutica and Clínica Integrada, Universidade Federal da Bahia, Canela Salvador, BA, Salvador, Brazil. albp@ufba.br
authors.forename: Antonio Luiz B
authors.initials: AL
authors.lastname: Pinheiro
authors.forename: Marleny Elizabeth M M
authors.initials: ME
authors.lastname: Gerbi
mesh_terms: D000818:Animals; D001861:Bone Regeneration / Q000528:radiation effects*; D001842:Bone and Bones / Q000502:physiology*; D006801:Humans; D053685:Laser Therapy; D014945:Wound Healing / Q000528:radiation effects*