Abstract
The purpose of this study was to investigate the temporal relationship between the masticatory force and the masseter muscles. Three subjects with normal stomatognathic function with the exception that a lower first molar was missing were selected. Three chewing gums differing in hardness were used as the test bolus, and masticatory force and electromyograms of the right and left masseter were recorded simultaneously. Masticatory force was measured using a 3-dimensional transducer mounted in a removable partial denture worn on the lower first molar.
1. With increasing gum hardness, burst duration (D) increased significantly. Burst duration (D) on the balancing side increased more than that on the working side.
2. At each gum hardness, duration from the onset of EMG to the appearance of masticatory force (D1) was almost constant. Duration from the appearance of masticatory force to the offset of EMG (D2) significantly increased on the balancing side, but tended to insignificantly increase on the working side.
3. Duration of resultant force (RD, RDP) was approximately constant.
4. Burst coordination pattern was roughly constant.
