Adaptive change in chewing-related brain activity while wearing a palatal plate: an functional magnetic resonance imaging study.

Prosthodontic treatment success depends on patients' ability to adapt to an altered oral environment containing removable prostheses. We investigated adaptive chewing-related brain activity changes in response to a new oral environment. Twenty-eight fully dentate subjects (mean age: 28.6 years) wore experimental denture-base palatal plates (3 mm thick), for 7 days. We measured food mixing ability and cycle time, and assessed brain activity by functional magnetic resonance imaging during chewing at pre-insertion (Day 0), and immediately (Day 1), 3 days (Day 3) and 7 days (Day 7) after insertion. Food mixing ability significantly decreased and cycle time increased on Day 1 as compared to Day 0 (P < 0.001) and tended to recover to Day 0 level by Day 7. Brain activation in the right face primary sensorimotor cortex and putamen significantly decreased on Day 1 as compared to Day 0 (P < 0.001) and recovered to Day 0 level by Day 7. Brain activation in the left face primary sensorimotor cortex, putamen, anterior cingulate gyrus (ACG) and right posterior medial frontal cortex (pMFC) significantly decreased on Day 1 as compared to Day 0 (P < 0.001) and did not recover by Day 7. Thus, oral environment changes involving palate covering affected chewing and induced adaptive brain activity changes in the face primary sensorimotor cortex and putamen, possibly associated with motor learning. As ACG and pMFC activity remained unrecovered by 7 days after plate insertion, automatisation of chewing while wearing a palatal plate may require longer adaptation periods.