Abstract
The purpose of the present study was to investigate the correlations between the increase of the biting force, EMG activities of the masticatory muscle and increase of the grip forces and EMG activities of the flex or anterior muscle of the forearm in term of the development from deciduous, mixed and permanent dentition.
A total of forty persons were investigated; 10 with deciduous dentition (designated as G1),10 with early mixed dentition (as G2),10 with late mixed dentition (as G3) and 10 with permanent dentition (as G4), none of whom had any gnatho-facial dysfunction. EMGs were taken from the right temporal and masseter muscles using bipolar surface electrodes, and the biting forces were measured at the right 2nd deciduous molars (G1, G2) and the right first permanent molars (G3, G4) using bite transducer. The grip forces were measured at the right hand using hand dynamometer and EMGs were takenfrom the right anterior flexion muscles with bipolar surface electrodes.
The results obtained in the present studies were as follows:
1) Though MBF (maximum bite force) showed an increase with age, it was more enhanced during the late mixed, and permanent dentition (G3, G4), when the first permanent molars function in chewing. Conversely the time required to reach MBF (MBFT) is decreased.
2) As the bite forces increased, speed for the maximum bite also acceralated, hence the momentary bite forces of the masticatory muscle increased with age.
3) As to the muscle activities between temporalis and masseter muscle, temporalis muscle activities were predominant during the deciduous and early mixed dentition period, then they shifted to the masseter muscle at the period of later mixed and permanent dentition, when the first molars function positively in chewing.
4) There are positive correlations between the maximum grip force (MGF), the speed of maximum grip (MGS), the maximum bite force (MBF), the speed of maximum bite (MBS). Biting forces were shown to be stronger than grip forces, similarly the momentary bite force was higher than the momentary grip force.
The results obtained in the present study disclosed that a noticeable increase in bite force and momentary bite force may depend on the prominent development of the masseter muscles occuring after later mixed dentition. Grip forces and momentary grip forces may also be associated with the muscle development of the forearm.
