Shape and size of the dental arch in populations aged 12 to 18 years of two Ecuadorian ethnic groups

Abstract

The shape of the dental arch and its intermolar distances between ethnicities can be different. Objective. To determine the shape and size of dental arches in populations aged 12-18 years, both sexes, of two Ecuadorian ethnic groups, Native Shuar and Mestizos, under conditions of normo-occlusion. Materials and Methods. Observational, cross-sectional study in 120 dental models distributed by ethnic group: 60 mestizos and 60 Shuar. To determine the size of the arch, the following were taken: intercanine width (AIC), intermolar width (AIM), anterior arch length (LA), upper and lower arch perimeter (PA) using a TRUPER-Stainless caliper. Arch shape was determined by overlaying OrthoForm-3M acetate insoles. The data were analyzed in the SPSS 25 program, in qualitative variables chi square was used and in the quantitative variables for parametric data Anova and T student; and for non-parametric Kruskall Wallis and Mann-Whitney. Statistical significance for all studies was 95%. Results and conclusions. In mestizos the predominant upper arch shape was oval (66.7%), then triangular (23.3%) and square (10.0%). The lower one was oval (56.7%), triangular (28.3%) and square (15.0%). In the Shuar, the predominant upper shape was oval (76.7%), triangular (20.0%) and square (3.3%). While the lower one was triangular (53.3%), oval (25.0%) and square (21.7%). The average of the distances in mestizos: AIC: 27.96mm, AIM: 49.5mm, PA: 92.49mm and LA: 15.61mm; in shuar: AIC: 28.14mm, AIM: 50.31mm, PA: 92.45mm and LA: 15.53mm, between these there were no significant differences except in the superior AIM. When comparing the distances between ethnic groups, it was obtained that there are no significant differences except in the upper intermolar distance, where higher values were found for the Shuar ethnic group. When comparing distances and lengths according to the arch shape in each ethnic group, for mestizos and Shuar, the upper and lower intermolar widths showed significant differences between arch shapes, with the oval being the one with the greatest distance. Differences were also found in the lower arc length for the Mestizo ethnic group.