Differences between high- and low-angle subjects in arch form and anterior crowding from 23 to 33 years of age.

The aim of this study was to compare changes in arch width and length in high- and low-angle subjects. The material comprised the cephalograms and study models of 17 males and 15 females with a high-angle and 12 males and 16 low-angle females. The age of the subjects at the first examination (T1) was 22 years 10 months and 22 years 8 months in the high-angle groups, 22 years 5 months and 22 years 8 months in the low-angle subjects, respectively, for males and females. The second assessment (T2) was 10 years and 9 years 10 months later in the high-angle and, 10 years 3 months and 9 years 10 months in the low-angle groups, respectively. Statistical analysis of changes for each group during the observation period T1-T2 was undertaken using a paired t-test, and the differences between the groups with two-sample t-tests. The findings showed a general reduction in upper and lower arch length, an increase of intermolar width, and a decrease of intercanine width in both genders. Anterior perimeter and anterior space in both angles decreased in both males and females. The mean changes were small, but with large individual differences. There were no significant differences between the genders or the high- and low-angle groups in the changes, except that the female high-angle group had a statistically significant (P = 0.05) greater decrease in mandibular arch length than the low-angle female group.