The relationship of dental crowding to tooth size, dental arch width, and arch depth.

This study was undertaken to answer the question, "Are there any differences in the mesiodistal tooth diameters, dental arch width and dental arch depth between the crowded and noncrowded dentitions?" The materials submitted for study consisted of the Orthoscan intraoral occlusograms of 89 subjects with well-aligned dentition and those of 74 subjects with gross dental crowding. The tooth size and arch dimensions were measured from these intraoral occlusograms. The data were subjected to statistical treatment for comparison of noncrowded and crowded groups. The findings in this study lead to the following conclusions: The mesiodistal tooth diameters of the crowded group were significantly larger than those of the noncrowded group. The dental arch widths of the crowded group were significantly smaller than those of the noncrowded group. No substantial or significant difference in dental arch depth between the crowded and noncrowded subjects could be noted. From these findings it seems that tooth size and dental arch width are determining factors in the formation of dental crowding. Clinically, these results suggest that in the treatment of dental crowding, extraction of teeth and/or expansion of dental arches should be considered depending on what is the main causative factor.