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KMID : 0361920120420020064
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Korean Journal of Orthodontics
2012 Volume.42 No. 2 p.64 ~ p.72
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Response of masticatory muscles to passive stretch stimulus - from perspectives of functional appliances
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Pae Eung-Kwon
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Abstract
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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 fi bers by using RT-PCR, western blot, and immunohistochemical assays.
Methods: Five male New Zealand White rabbits were fi tted 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 sacrifi ced aft er 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 aft er 7 days.
Conclusions: Th e transition of fi ber phenotypes in response to a stretch stimulus may take longer in the masticatory muscles than in the limb muscles.
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KEYWORD
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Extensor digitorum longus, Masticatory muscles, Myosin heavy chains, Stretch
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