The purpose of this research was to clarify the difference between the children who can or cannot chew and swallow properly, by observation of eating behavior and by measurement of masticatory function.
The examinees were 107 children in a kindergarten in Tokyo. For assessment of their eating behavior, the attitudes and behavior of each child during lunch were observed, and features of the behavior were recorded. The children were classified into two groups, one with and the other without abnormal chewing and swallowing habits, by the teachers of the kindergarten. Regarding masticatory function, electromyograms of masseter and temporal muscles were recorded for five sample foods. Chewing gum masticating test, biting force, and occlusal contact area were evaluated.
1. 37 children were included in the group with abnormal chewing and swallowing habits by the teachers, and the others (70) were put the group with no problems. Eating behaviors observed in these examinees were analyzed in the two groups by Hayashi's guantification method II, and the highest partial correlation (0.583) was observed for slow eating.
Compared with the group with no problems, the group with abnormal habits showed more number of masticatory strokes and longer time in chewing sample food, and thus, they seemed to be confirmed as slow eaters functionally. However, no statistically significant differences between the two groups were observed in masticatory rhythm, which is one of the important factors in slow eating.
2. Eating behavior was analyzed by Hayashi's quantification method III, and as result, the children were classified into three groups, A (44 children), B (38), and C (25).
Children in group A seemed to have no or minimal problems in their eating behavior. Assessment of masticatory function showed that they had the lowest number of strokes and shortest time among the three groups in mastication of sample foods. Electromyograms of this group showed smaller variations in rhythm and greater muscle activity than the other two groups. This group showed maximal value in biting force and widest area of occlusal contact. These findings suggest that children who had no problems in their eating behavior had well-matured masticatory function.
In Children in group B, masticatory activity was frequently interrupted with no concentration of the attention on food, and the foods were just kept in their mouth, though they had an active attitude toward the meal. In assessment of masticatory function, children in group B exhibited lower muscle action potentials in electromyograms and weaker biting force than the other two groups, which seemed to suggest that they had problems in development of masticatory muscles.
Eating behavior of children in group C was characterized by the lack of interest in the meal. They were all slow eaters. Analysis of masticatory function revealed that this group had the highest number of strokes and the longest time among the three groups for chewing sample food. Electromyograms showed highest coefficients of variation in the duration, the cycle, and the mean muscle action potentials among the three groups. This group exhibited lower biting force than group A, but no statistically significant differences were observed. These findings show that children in group C had greater intra-group variation in rhythm and muscle activity during mastication, which seemed to suggest that lacked interest in the meal, which was caused by everyday eating habits rather than by under development of masticatory muscles.