title: Evaluation of two protocols for low-level laser application in patients submitted to orthodontic treatment.
abstract: BACKGROUND
  Different low-level laser (LLL) irradiation protocols have been tested to accelerate orthodontic tooth movement (OTM). Nevertheless, divergent results have been obtained. It was suggested that the stimulatory action of low level laser irradiation occurs during the proliferation and differentiation stages of bone cellular precursors, but not during later stages.
  
  
  OBJECTIVE
  The purpose of this study was to determine the effect of two protocols of LLL irradiation on experimental tooth movement: One with daily irradiations and another with irradiations during the early stages.
  
  
  METHODS
  Thirty-six rats were divided into control groups (CG1, CG2, CG3) and irradiated groups (IrG1, IrG2, IrG3) according to the presence of: experimental tooth movement, laser irradiation, type of laser irradiation protocol and date of euthanasia (3th or 8th day of experiment). At the end of experimental periods, a quantitative evaluation of the amount of OTM was made and the reactions of the periodontium were analyzed by describing cellular and tissue reactions and by counting blood vessels.
  
  
  RESULTS
  The amount of OTM revealed no significant differences between groups in the same experimental period (p < 0.05). Qualitative analysis revealed the strongest resorption activity in irradiated groups after seven days, especially when using the daily irradiation protocol. There was a higher number of blood vessels in irradiated animals than in animals without orthodontic devices and without laser irradiation (p < 0.05).
  
  
  CONCLUSIONS
  Moreover, angiogenesis was verified in some of the irradiated groups. The irradiation protocols tested were not able to accelerate OTM and root resorption was observed while they were applied.
authors.affiliation: Department of Orthodontics, UFRJ.
authors.forename: Mariana
authors.initials: M
authors.lastname: Marquezan
authors.forename: Ana Maria
authors.initials: AM
authors.lastname: Bolognese
authors.forename: Mônica Tirre de Souza
authors.initials: MT
authors.lastname: Araújo
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D028022:Low-Level Light Therapy / Q000379:methods*; D018919:Neovascularization, Physiologic / Q000528:radiation effects*; D010513:Periodontal Ligament / Q000098:blood supply / Q000166:cytology / Q000528:radiation effects*; D051381:Rats; D012391:Root Resorption; D014087:Tooth Movement Techniques / Q000379:methods*
keywords: Angiogenesis inducing agents; Lasers; Low-level laser therapy; Tooth movement