title: Effects of two wattages of low-level laser therapy on orthodontic tooth movement.
abstract: BACKGROUND
  Mixed outcomes have been found in animal and clinical studies with regard to the use of low-level laser therapy (LLLT) as a modality to accelerate orthodontic tooth movement (OTM). One major reason for the variable findings is the different methodologies and protocols for laser therapy use.
  
  
  OBJECTIVE
  The aim of this study was to determine whether orthodontically moved molars exposed to two different wattages at the same energy density of LLLT exhibited differences in the amount of tooth movement and molecular and histological changes in the adjacent periodontal areas.
  
  
  METHODS
  An orthodontic force was applied to rat upper first molars exposed to 500mW (EX-500) and 1000mW (EX-1000) of laser application, with a control group (CT) with no laser application. Gene expression in the periodontal ligament (PDL) and histology of the palatal gingiva of the molars were analyzed.
  
  
  RESULTS
  There was a statistically significant difference for OTM between EX-500 but not between EX-1000 and CT groups. RANKL and MMP-13 expression levels in the PDL of orthodontically moved molars, however, were increased significantly in laser-exposed groups compared to CT. Early signs of dysplasia were observed in over half of the animals in the EX-1000 group.
  
  
  CONCLUSIONS
  Our results provide evidence for molecular changes and the potential dysplastic effects of laser on the surrounding soft tissues. Further studies are needed to better identify an optimum laser protocol to maximize the desired effect.
authors.affiliation: Discipline of Orthodontics, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Milligan
authors.affiliation: Dental Research Institute, Faculty of Dentistry, University of Toronto, Canada.
authors.forename: Y
authors.initials: Y
authors.lastname: Arudchelvan
authors.affiliation: Discipline of Orthodontics, Canada; Dental Research Institute, Faculty of Dentistry, University of Toronto, Canada. Electronic address: sg.gong@dentistry.utoronto.ca.
authors.forename: S-G
authors.initials: SG
authors.lastname: Gong
mesh_terms: D000818:Animals; D005881:Gingiva / Q000378:metabolism / Q000528:radiation effects; D028022:Low-Level Light Therapy / Q000379:methods*; D008297:Male; D053509:Matrix Metalloproteinase 13 / Q000378:metabolism; D008963:Molar; D010513:Periodontal Ligament / Q000378:metabolism / Q000528:radiation effects; D053245:RANK Ligand / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D060888:Real-Time Polymerase Chain Reaction; D014087:Tooth Movement Techniques / Q000379:methods*; D015854:Up-Regulation
chemical_list: D053245:RANK Ligand; D053509:Matrix Metalloproteinase 13
keywords: Epithelial hyperplasia; LLLT; MMP-13; Periodontal ligament; Photobiomodulation; RANKL