Abstract
This investigation was made in order to serve as an aid in the diagnosis and prognosis of mandibular protrusion in the deciduous dentition from the standpoint of the correlation between form and function. The subjects consisted of 14 preschool children whose lower jaws were protruded (SNA angle of these subjects were over 80.0 degrees). The controls, so called normal occlusion, consisted of the same number of preschool children. Electromyographs (EMG) were recorded bilateraly on the anterior temporal muscle (TA), the posterior temporal (TP) and the superficial portion of the masseter (M), during the gum and peanuts free chewing and max. biting. Maximum amplitudes were measured on 20 strokes in each chewing and on 5 strokes in max. biting. Thereupon, the _??_and_??_ratio and TA%, TP%, M% were calculated in each chewing and max. biting. These EMG data of the mandibular protrusion group were compared with that of the normal occlusion group. The correlation coefficiets among EMG data and cephalometric data in the mandibular protrusion group and the normal occrusion group, were calculated. The results obtained are summaried as follows
