Objectives: Describe the pattern of shape variation of the mandibular dental arch in a sample from the Metropolitan Region through an observational, cross-sectional study. Methods: 18 landmarks on 134 standardized photographs of dental casts were digitized, and a Procrustes analysis was performed. Results: The size of the centroid in men was significantly larger than in women. Discriminant analysis with gender cross-validation did not show significant differences in the shape components. The variation pattern in the shape of the dental arches is mainly explained by PC1 (50.1% of the total variation, anteroposterior variation) and PC2 (13.3%, transverse variation). Conclusions: Given the morphological continuity that is observed when performing a statistical analysis of the variation pattern in shape and size of the arch applying geometric morphometric tools, the use of preformed templates for determining the shape of the dental arch should be reconsidered.