Study of adaptability to oral environmental changes from brain plasticity perspective

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Nine subjects (mean age 28.7) underwent fMRI during chewing gum on the left side of jaw, with and without a resin cap on the lingual region of the maxillary left canine. fMRI acquisition protocol used in the present study has been optimised in our pilot study. fMRI was performed before, immediately after and 30min after applying resin cap. Six out of nine subjects were asked to masticate a wax cube on the left side of jaw in each condition to determine masticatory efficiency. fMRI data were analyzed with SPM2 (Statistical Parametric Mapping 2) to determine differences of brain activity (p=0.001 uncorrected, extent threshold=20voxels).During left side gum chewing, bilateral cerebellar posterior lobe and the proximal part of right supramarginal gyrus were more activated immediately after applying resin cap than before applying it. The activation of cerebellum might show the activity of cerebellum during "motor learning". During left side gum chewing, right cerebellar posterior lobe were less activated 30min after applying resin cap than immediately after applying it. This result might show that the motor learning of left masticatory muscles and the adaptation to left gum chewing with regin cap were achievement.The brain regions showing negative correlation to masticatory efficiency were bilateral postcentral gyrus, left precentral gyrus, right cingulate gyrus, right superior temporal gyrus, right cerebellar posterior lobe and right cerebellar anterior lobe. These findings suggest that right cerebellar posterior and anterior lobe were activated to achieve motor learning of left masticatory muscles to remedy reduced masticatory efficiency immediately after applying resin cap, and were less activated with the improvement of masticatory efficiency and achievement of motor learning 30min after applying resin cap.