Changes in occlusion between 23 and 34 years.

The purpose of this study was to examine occlusal changes in the adult dentition. Study models made at average ages of 23 and 34 years of 64 females and 80 males of Norwegian descent were measured. None of the subjects underwent orthodontic treatment or surgery during the observation period. The means of the measured changes were small, with none exceeding 0.55 mm, and were larger in males than in females. The most obvious finding in both sexes was a decrease of up to 2.5 mm in the mandibular anterior perimeter, with very few subjects showing an increase. Significant changes were found in mandibular intercanine width and intermolar distance in both arches. A significant decrease in maxillary arch perimeter was seen in females, but with smaller values than in the mandibular arch. Overjet and overbite decreased significantly only in males. For each variable in each sex, some subjects showed decreases and others showed increases, indicating that individual prediction may be difficult. However, very few subjects demonstrated increased space in the anterior segments.