OBJECTIVETo study the mechanism in masticatory muscle dysfunctional induced by hemimastication.

METHODSCa2+ contents were measured with atomic absorption spectrometry; calcinuerin were measured with colorimetric method; muscle fiber types were measured with adenosine-triphosphate (ATPase) staining.

RESULTS(1) Compared with the controls, Ca2+ contents in experimental group had the higher level except 8 weeks (P < 0.05). (2) The ratio of slow fiber in experimental group increased, higher than the match groups (P < 0.05). (3) With Ca2 contents rise, the activities of calcinuerin present a bell-like shape. (4) The ratio of slow-type fiber was positively correlated to the activities of calcinuerin (r = 0.876, P < 0.05).

CONCLUSIONThe signal way of muscle fiber growth and fiber transformation were activated by high concentration of calcium, then, muscle fiber transferred from fast to slow type. It may play an important role in the mechanism that hemimastication result in masticatory muscles dysfunction.