The relationship of crowding to the eruptive position of the lower permanent incisors.

The aim of this study was to examine the positions of newly erupted lower permanent incisors and their relationship to crowding. Forty-one crowded and 37 uncrowded dental casts of children in the early mixed dentition were examined by means of digitization using a reflex microscope. Two aspects of alignment were considered: rotation and labio-lingual displacement. Rotations of the incisors were defined as deviations from 'ideal' predicted angles. Displacement of the incisors was measured as the distance between the most labial and most lingually placed incisors. The study showed an increase in rotations amongst the crowded sample. The result of the investigation of the relationship between crowding and displacement was inconclusive. There would appear to be significant differences between the positions of newly erupted crowded and uncrowded incisors. Crowding, however, was not the only factor causing irregularity.