Abstract
Since mastication is one of the most important mandibular functions, much attention has been paid to this. Numerous reports, which analyzed this function from the viewpoint of the mandibular movement, have been published on this subject, and the dividing of this masticatory movement into its component cycle has been mandatory in such studies. Although the method to divide these movements greatly influenced the results, less attention has been paid, especially with respect to children with primary dentition. In this study an appropriate method to divide the masticatory movement into component cycles was sought in order to apply this to children.
The subject group for children with primary dentition consisted of 9 girls ranging in age from 4 to 6 years. They were instructed to chew gum. The mandibular movement at the lower incisal point was recorded and analyzed to find the best method for dividing of the chewing movement. First, the best frame for the terminal position of each component cycle was looked for, using two conditions, namely the method to smooth the mandibular movement and a cycle duration. Next, it was examined whether the maximum opening positions, which existed between the terminal positions, would be appropriate. The number of cycles divided from the masticatory movements using these two steps compared with the number of cycles visually recognized as a cycle. In addition,27 women, ranging in age from 16 to 27 years, also participated in this study. Comparison between children with primary dentition and adults with permanent dentition was carried out.
1) More than 99% of the terminal positions were able to be recognized automatically by the smoothing method and minimum cycle duration in children.
2) The same method was applicable to adults with permanent dentition, though the minimum cycle duration was not the same in case of children with primary dentition.
3) Movements, which were not considered as an active chewing cycle could be excludable from the masticatory movement using the condition both of the terminal position and the vertical position of the lower incisal point.
