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

Triviño T, Siqueira DF, Scanavini MA

Methodist University of São Paulo, São Bernardo do Campo, São Paulo, Brazil. tarcilatrivino@uol.com.br

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.

Published 4 January 2008 in Am J Orthod Dentofacial Orthop, 133(1): 10.e15-22.
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