Fourier Analysis of Dental Arch Morphology in South Australian Twins
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Our aims were to assess the suitability of Fourier harmonics in describing dental arch form in South Australian twins and to estimate the contribution of genetic factors to observed variability. Dental casts of 37 monozygous (MZ) and 19 dizygous (DZ) twin pairs were selected, all subjects being male Caucasians with minimal dental crowding and no history of orthodontic treatment. There were no significant differences between the groups in any of the Fourier co-efficients. In the variance of differences between twins the constant value a<sub>0</sub> and first amplitude had significant genetic variances at the level of 5% or less. The highest correlations within MZ pairs (r>0.72) were for a<sub>0</sub>, representing arch size, and for the first and second Fourier amplitudes (amp<sub>1</sub> and amp<sub>2</sub>), representing the arch depth/arch breadth ratio and the relative taper of the arch respectively, in both the maxillary and mandibular arches. The results of this study confirm that the Fourier method provides an accurate, reproducible method for describing dental arch size and shape, and suggest that genetic factors contribute mainly to the variation in arch size and to arch depth/arch breadth ratio rather than to other aspects of dental arch morphology.