A new concept of mandibular dental arch forms with normal occlusion.

INTRODUCTION

Because it is important to maintain dental arch dimensions during orthodontic therapy, all possible dental arch forms must be evaluated.

METHODS

A mathematical method associated with a polynomial function was used to evaluate the dental arch forms of 63 mandibular models of Brazilian adolescents in the permanent dentition with normal occlusion. A bead was glued to each tooth to simulate an orthodontic accessory and help in the measurement of distances between the center of the bead to the x- and y-axes. The dental casts were digitized, and images were plotted on a computer program to obtain the sixth-degree polynomial and the graph of this function. These segments were organized into 8 groups according to the form of the anterior curve of the dental arch; these were named forms A through H. Each group was subdivided into 3 subgroups: small, medium, and large sizes.

RESULTS

Form A was the most frequently observed at 22%, whereas form G was observed in only 2% of the total sample. Forms A, B, C, D, E, and F had more curve segments in medium size, and forms G and H had more curves in small size. A mean dental arch curve was calculated; however, this form coincided with form C, which had an incidence of 10%.

CONCLUSIONS

The mandibular dental arch is represented by 23 forms; thus, a normal dental arch cannot be represented by only 1 simple arch form.