Abstract
Study models of 20 cases of crowding of the upper incisors in the mixed dentition period before treatment were used as materials. Space analyses were conducted to predict the possibility of proper alignment of the upper arch of the early permanent dentition quantitatively, and the relationship between the space analysis and the result of the upper arch alignment after treatment was considered. Ono's simple regression analysis was used to calculate the required arch length, and two methods were adopted to measure the available arch length after assuming the easement of the crowding of the upper incisors. One was the conventional segment method in which both the linear incisor and buccal arch lengths were added up, while the other was the preformed wire method that is proposed in this paper.
The results were as follows;
1. Differences between the estimated values of the required arch lengths and their measured values in the permanent dentition were so small that they were sufficient to be within the clinical tolerance level.
2. Even in the cases in which proper alignment of the upper arch in the early permanent dentition was acquired, there were many cases in which the segment method had shown the negative results of 2,3 mm at one side.
3. It seemed that the analyses of the preformed wire method reflected roughly the results of the upper arch alignment in the early permanent dentition.
4. In cases in which morphological distortions of the upper arch were relatively slight, the differences between the two methods of calculating the available space were small. On the other hand, in cases in which the morphologies of the upper arch were V-shaped, the differences between the two methods tended to become larger.
5. It seems that applying the results of the segment method into practice directly should be restricted and the preformed wire method, leaving a little room for improvement, was applicable to the space analysis of upper incisor crowding cases.
