An Investigation of Dental Arch Form in a Sample of Malocclusions

Abstract

The objective of this study was to investigate the geometric arch forms found in a sample of malocclusions. The specific objectives were to determine if there was a basic geometric arch form which described all of the sample, to identify the typical arch form in each of the classes of malocclusion, and to determine if there was a statistical difference in form among the various classes in each arch. A sample of 99 maxillary and mandibular plaster casts were collected from the Department of Orthodontics, Indiana University School of Dentistry, and classified according to Angle's classification of malocclusion. Occlusograms were taken of all casts. The center of incisal edges, cusp tips of cuspids and bicuspids, and bifurcation of molars were marked and traced on acetate tracing paper from the occlusogram). A straight line was drawn between these points giving the final dental arch form. A coordinate· system was established on each arch form which allowed the classification of the arch form by Hayashi's method 60. The results showed that no basic arch form described the sample. The average arch form for each classification of malocclusion varied between classes and between arches. Statistically, maxillary arch form of the Class II division 2 differed significantly from maxillary Class I, Class II division 1, and Class III malocclusions. Class II division 2 mandibular arch form differed significantly only from the mandibular Class I malocclusion.