Abstract
The purpose of this study was to investigate the influences of habitual side chewing and the characteristics of food on the masticatory muscle function in children.
A total of thirty persons were subjected to the study; 10 with deciduous dentition (designated as G1),10 with mixed dentition (as G2),10 with permanent dentition (as G3), none of whom had any gnatho-facial dysfunction. EMGs were recorded from the temporal anterior muscles and masseter muscles on both sides, and the mandibular movement on the frontal plane was recorded during chewing of boiled fish cake paste, chewing-gum and chewing of dried cuttlefish on both the habitual side and the non-habitual side. EMG activities obtained and periods of closed phase, occlusal phase and open phase in the pathway of the mandibular movement were measured with a personal computer system. The relationship between the total muscle activities at clenching in the intercuspal position and the total muscle activities at chewing were also evaluated.
The results obtained in the present study were as follows:
1) Influence of habitual side chewing on the rhythm of the mandibular movement during chewing of chewing-gum was not found in all groups. Influence on EMG activities was not found in G1 and G2, but were presented in G3.
2) Influence of the character of food on rhythm of mandibular movement was not clear in G1, but as found in the other groups, while EMG activities were influenced by the character of food in all groups.
3) The MA Index (the ratio of total muscle activities while chewing to total muscle activities at clenching) showed a decrease with age. As far as the results of the present study is concerned, it could be suggested that the proficiency of the chewing ability is dependent on the dentitional growth. Furthermore, the MA Index was considered to be appropriate for evaluating the masticatory muscle function in children.
