title: Combined effect of photobiomodulation with a matrix metalloproteinase inhibitor on the rate of relapse in rats.
abstract: OBJECTIVE
  To investigate combined effect of photobiomodulation with a matrix metalloproteinase (MMP) inhibitor on the relapse rate in relation to MMP expression in rats.
  
  
  METHODS
  Fifty-two rats were divided into four groups according to the treatment modality: control group, irradiation group, doxycycline group, and irradiation with doxycycline group. During a relapse period of 5 days after orthodontic movement, maxillary central incisors were treated by low-level laser therapy (LLLT) as a photobiomodulation and/or doxycycline as a synthetic MMP inhibitor. Relapse rate was evaluated in association with MMP expression at the gene and protein levels.
  
  
  RESULTS
  Relapse rates were increased by LLLT (1.57-fold) and decreased by doxycycline (0.83-fold) compared with the control, showing positive correlation with the levels of expression for all MMPs in the periodontal ligament (PDL). LLLT concomitant with doxycycline administration resulted in no significant differences of relapse rate and MMP expression from the control.
  
  
  CONCLUSIONS
  The combined effect of photobiomodulation with an MMP inhibitor around the relapsing teeth proved to be antagonistic to PDL remodeling activity during relapse. This study suggests a basis for developing a novel biologic procedure targeting the MMP-dependent PDL remodeling to control the relapse rate.
authors.affiliation: a  Postgraduate student, Department of Orthodontics, Kyung Hee University Graduate School, Seoul, Korea.
authors.forename: Sang-Hyun
authors.initials: SH
authors.lastname: Lee
authors.affiliation: b  Clinical Instructor, Department of Orthodontics, Kyung Hee University Dental Hospital, Seoul, Korea.
authors.forename: Kyung-A
authors.initials: KA
authors.lastname: Kim
authors.affiliation: c  Graduate student, Kyung Hee University Graduate School, Seoul, Korea.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Anderson
authors.affiliation: d  Assistant Professor, Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Korea.
authors.forename: Yoon-Goo
authors.initials: YG
authors.lastname: Kang
authors.affiliation: e  Associate Professor, Department of Orthodontics, Kyung Hee University School of Dentistry, Seoul, Korea.
authors.forename: Su-Jung
authors.initials: SJ
authors.lastname: Kim
mesh_terms: D000818:Animals; D004318:Doxycycline / Q000494:pharmacology; D028022:Low-Level Light Therapy; D061965:Matrix Metalloproteinase Inhibitors / Q000494:pharmacology*; D010513:Periodontal Ligament / Q000378:metabolism* / Q000528:radiation effects; D051381:Rats; D012008:Recurrence; D014087:Tooth Movement Techniques
chemical_list: D061965:Matrix Metalloproteinase Inhibitors; D004318:Doxycycline
keywords: Doxycycline; Orthodontic relapse; Photobiomodulation