Abstract
A method for determining the mandibular rest position in twenty-eight children with normal occlusion in the II A stage of Hellman's dental age was devised with the amplitude-histogram.
With this method, suitable ways for guiding the rest position were investigated and the mean values of the free way spaces on each guiding method as well as in each age group were calculated and compared with each other.
To the children with anterior cross-bite in the primary dentition the method was also applied for evaluating its usefulness to the functional analysis on such malocclusions.
The results were as follows:
1. The method based on the principle of the amplitude-histogram was found to be useful for determining the mandibular rest position of the younger children in primary dentition stage.
2. Even for disobedient children the method could be applied and the voluntary mandibular rest position was noticed as the only usable way among the three for such children.
3. Among the mean values of the free way spaces at each age, those in the rest position after swallowing tended to be the smallest and those in the rest position after opening the mouth the largest.
However, a significant difference among their values was only noticed in five year old children.
4. The mean value and its variance of free way spaces tended to decrease with age.
5. The suitable methods for guiding the mandibular rest position were different according to age, the voluntary rest position for three year old children, the rest position after swallowing and the voluntary for four year old children, and the rest position after swallowing for five year old children respectively.
6. The values of free way spaces of children with the skeletal type anterior cross-bite in primary dentition were significantly smaller than those of children with normal occlusion. In contrast with the above, the children with the functional type anterior cross-bite or with the mixed type occlusion were suggested to have greater values than those of children with normal occlusion.
