Abstract

Aim
The purpose of the present research was to evaluate the variations in the shape of maxillary
and mandibular dental arches in a population undergoing orthodontic treatment.
Methodology
Dental casts of 133 white subjects (61 males, 72 females; ages 10.6–26.6) were scanned and
digitized in three dimensions. Landmarks were placed on the incisal margins and on the cusps
of canines, premolars, and molars. Geometric morphometric methods were applied
(Procrustessuperimposition and principal component analysis). Sexual dimorphism and
allometry were evaluated with permutation tests and age–size and age–shape correlations
were computed. Two block partial least squares analysis was used to assess covariation of
shape.
Results
The first four principal components represented shape patterns that are often encountered and
recognized in clinical practice, accounting for 6–31 per cent of total variance. No shape
sexualdimorphism was found, nevertheless, there was statistically significant size difference
betweenmales and females. Allometry was statistically significant, but low (upper: R2 =
0.0528, P < 0.000, lower: R2 = 0.0587, P < 0.000). Age and shape were weakly correlated
(upper: R2 = 0.0370, P = 0.0001, lower: R2 = 0.0587, P = 0.0046). Upper and lower arches
covaried significantly (RV coefficient: 33 per cent).