Tooth-position, arch-size, and arch-shape in the primary dentition

Tooth positions and dental arch forms are related to the growth of the cran iofacial complex. To determine the positions of primary teeth and size and shape of the primary dental arches, sixty dental casts of young children (t hirty boys and thirty girls) with normal occlusions were examined. In all c asts the coordinates of cusp tips of primary canines and molars, and mesial and distal Line angles of primary canines and incisors were digitized. The computer-generated curves were made for the maxillary and mandibular arche s using a polynomial model. The results show that there were three major cu sp-to-fossa and one cusp-to-marginal ridge relations in primary molar inter cuspation. On average, girl's dental arches were smaller than boy's dental arches. The mean curves of maxillary and mandibular arches were similar in posterior segments, but the curves of mandibular arches in anterior segment s were gentler than those of maxillary arches.