Reversible Effects of Functional Mandibular Lateral Shift on Masticatory Muscles in Growing Rats

In this study, we aimed to determine the effects of functional mandibular lateral shift (FMLS) on muscle mass, fiber size, myosin heavy chain type, and related gene expression in masticatory muscles (masseter temporalis), as well whether baseline levels could be recovered after FMLS correction growing rats. The appliance was placed mandible leftward by approximately 2 mm. After placement for 4 weeks, left side had significantly lower wet weight, mean cross-sectional area, proportion type IIa fibers than those right or control groups (p < 0.05), with downregulation upregulation IGF-1 GDF-8 expression, respectively 0.05). Following weeks devoted recovery from FMLS, parameters group were not different group, left-side enhanced simultaneously suppressed. These findings indicate that changes induced via tend revert normal conditions if intervention is eliminated at an early stage. Therefore, appropriate orthodontic treatment during growth period advisable prevent asymmetric alterations muscles.