[Mandibular movement during chewing-gum chewing on the sagittal plane in children]

The purpose of this study was to investigate the changes of the mandibular movement during chewing-gum chewing in subjects ranging from children with deciduous dentition to adults with permanent dentition, and also to analyze the influences of malocclusion on the mandibular movement in children. The subjects were divided into three groups based on the developing stage of the dentition: ie., i) 7 children; mean age 4.6 yrs-with deciduous dentition, ii) 9 children; mean age 9.0 yrs with mixed dentition and iii) 10 adults; mean age 22.9 yrs with permanent dentition. In addition, 17 subjects who have malocclusion were also examined, who were subdivided into the cross-bite group (mean age 7.9 yrs) and progenia group (mean age 7.3 yrs). The mandibular movements were recorded with Saphon Visi-Trainer CII during chewing-gum chewing and the traces of mandibular movement recorded on the sagittal plane were then analyzed. The results obtained in the present study are summarized as follows; 1) The chewing pattern of children with deciduous dentition was characterized by narrow width and large posterior deviation of the opening and closing pathway. During growth, the width of the pathways increased and their posterior deviation decreased. The narrow width of the opening and closing pathways form the majority of the type of chewing pattern in children with deciduous dentition. On the other hand, the types of reversed and crossed pathways form the majority in adults. 2) The chewing pattern in children with malocclusion was characterized by small posterior deviation in the pathway. The type of reversed cycle was ranked first among the chewing patterns of progenia patients, while there were no significant differences of chewing types between cross-bite patients and children with normal occlusion. As far as the results of the present study is concerned, the changes of the mandibular movement on the sagittal plane following the dentitional growth were characteristic indicated. In addition, malocclusion such as cross-bite and progenia observed in the children may influence the chewing pattern.