Late lower arch crowding in relation to the direction of eruption.

The change in lower arch crowding 3-4 years after second permanent molar eruption was examined in 85 subjects, in relation to the angulation and change in angulation of molars and incisors relative to the mandibular plane using correlation and multiple regression analyses. Crowding increased significantly during the observation periods. Changes in molar and incisor angulation in both mesial and distal directions were observed. The increase in crowding was not related to molar or incisor angulation at 12 years. Some association between increase in crowding, reduction in arch depth and retroclination of incisors was found.