Biometric study of tooth size in normal, crowded, and spaced permanent dentitions.

INTRODUCTION: At present, there is a void in the orthodontist's armamentarium with regard to the assessment of malocclusion due, in part, to tooth size. A biometric study of tooth size was carried out to examine the extent to which tooth size contributes to dental crowding or spacing.

METHODS: A sample of 240 orthodontic study casts was selected from a larger sample. These casts met the selection criteria. The sample was divided into crowded, spaced, and normal dentition groups with 80 casts in each group. The criterion of grouping was based on the tooth size-arch length discrepancy in the arch. Each group comprised 40 maxillary and 40 mandibular casts that were further divided equally by sex. The data were statistically analyzed.

RESULTS: Mesiodistal crown dimensions of individual teeth, the sum of the incisors, and the sum of the canines and the premolars were uniformly larger in crowded arches than in normal and spaced dentition groups. Mesiodistal crown dimensions of individual teeth were smaller in the spaced arches compared with normal dental arches, but the difference was significant only in the combined mesiodistal crown dimensions of the mandibular incisors. Correlations of the combined mesiodistal crown dimensions of the incisors with the combined mesiodistal crown dimensions of the canines and the premolars were positive in all 3 groups.

CONCLUSIONS: Mesiodistal tooth size is an important factor in the assessment of crowding or spacing and in orthodontic treatment planning.