title: Response of masticatory muscles to passive stretch stimulus - from perspectives of functional appliances.
abstract: OBJECTIVE
  The aims of this study were to examine whether a passive stretch stimulus by means of a functional appliance induces changes in the fiber composition of masticatory muscles and whether these changes are similar to the changes in stretched limb muscle fibers by using RT-PCR, western blot, and immunohistochemical assays.
  
  
  METHODS
  Five male New Zealand White rabbits were fitted with a prefabricated inclined plane on the maxillary central incisors to force the mandible forward (- 2 mm) and downward (- 4 mm). Further, 1 hind limb was extended and constrained with a cast so that the extensor digitorum longus (EDL) was stretched when the animal used the limb. The animals were sacrificed after 1 week and the masseter, lateral pterygoid, and EDL were processed and compared with those from control animals (n = 3).
  
  
  RESULTS
  The stretched EDL had a significantly higher percentage of slow fibers, whereas the stretched masticatory muscles did not show changes in the composition of the major contractile proteins after 7 days.
  
  
  CONCLUSIONS
  The transition of fiber phenotypes in response to a stretch stimulus may take longer in the masticatory muscles than in the limb muscles.
authors.affiliation: Department of Orthodontics and Pediatric Dentistry, University of Maryland, School of Dentistry, Baltimore, MD, USA.
authors.forename: Eung-Kwon
authors.initials: EK
authors.lastname: Pae
keywords: Extensor digitorum longus; Masticatory muscles; Myosin heavy chains; Stretch