title: Low-level laser therapy enhances the stability of orthodontic mini-implants via bone formation related to BMP-2 expression in a rat model.
abstract: OBJECTIVE
  The aim of this study was to investigate the stimulatory effects of low-level laser therapy (LLLT) on the stability of mini-implants in rat tibiae.
  
  
  BACKGROUND
  In adolescent patients, loosening is a notable complication of mini-implants used to provide anchorage in orthodontic treatments. Previously, the stimulatory effects of LLLT on bone formation were reported; here, it was examined whether LLLT enhanced the stability of mini-implants via peri-implant bone formation.
  
  
  METHODS
  Seventy-eight titanium mini-implants were placed into both tibiae of 6-week-old male rats. The mini-implants in the right tibia were subjected to LLLT of gallium-aluminium-arsenide laser (830 nm) once a day during 7 days, and the mini-implants in the left tibia served as nonirradiated controls. At 7 and 35 days after implantation, the stability of the mini-implants was investigated using the diagnostic tool (Periotest). New bone volume around the mini-implants was measured on days 3, 5, and 7 by in vivo microfocus CT. The gene expression of bone morphogenetic protein (BMP)-2 in bone around the mini-implants was also analyzed using real-time reverse-transcription polymerase chain reaction assays. The data were statistically analyzed using Student's t test.
  
  
  RESULTS
  Periotest values were significantly lower (0.79- to 0.65-fold) and the volume of newly formed bone was significantly higher (1.53-fold) in the LLLT group. LLLT also stimulated significant BMP-2 gene expression in peri-implant bone (1.92-fold).
  
  
  CONCLUSIONS
  LLLT enhanced the stability of mini-implants placed in rat tibiae and accelerated peri-implant bone formation by increasing the gene expression of BMP-2 in surrounding cells.
authors.affiliation: Department of Orthodontics, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Omasa
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Motoyoshi
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Arai
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Ejima
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Shimizu
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000502:physiology*; D054023:Lasers, Semiconductor / Q000627:therapeutic use; D028022:Low-Level Light Therapy; D008297:Male; D052280:Orthodontic Anchorage Procedures; D016348:Osseointegration; D010012:Osteogenesis / Q000502:physiology*; D016133:Polymerase Chain Reaction; D019736:Prostheses and Implants; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000502:physiology / Q000601:surgery*; D014025:Titanium
chemical_list: D055396:Bone Morphogenetic Protein 2; D014025:Titanium