Association Study of Ancestry and Cephalometric Measurements in Northwest Colombia

Objectives: Our aim was to evaluate the relationship between cephalometric measurements and genetic ancestry in a sample from Antioquia.
Methods: Analytical cross-sectional study was conducted with unrelated adults (n=68). Cephalometric landmarks were identified on lateral X-ray films from clinical records. Calibration of operators was performed, yielding an 89.9% Kappa index. Afterwards, 48 linear and angular cephalometric measurements were identified using a protractor. Variables were grouped in 7 categories: cranial base/skeletal, maxillary skeletal, mandibular skeletal, maxillomandibular relations, vertical relations, dentoalveolar and soft tissue.
DNA sample were genotyped for 20 autosomal Ancestry Informative Markers by PCR. Autosomal admixture proportions were estimated by ADMIXMAPv3.8.
The association with the ancestry variable was determined based on the ancestral component European, recorded as high and low established on the 50th percentile. Since the normality test Shapiro-Wilk showed that 28 variables distributed normally, they were analyzed using Student′s t-test while the remaining 20 variables were tested with the Mann-Whitney U-test.
Results: Average admixture proportion was 67,23% European, 10,77% African and 22,08% Native-American, which is in accordance to our previous studies. Statistically significant differences were founded in SNA being higher in the low European group (p=0.15) and in Go-Gn/S-N, Go-Me/FH and WITS measurements with higher values for the high European group (p=0.018, p=0.04 and p=0.028 respectively). The increase in Go-Gn/S-N and Go-Me/FH angles in the high European group represent larger pattern of vertical rotation of the jaw, which are in agreement with literature reports.
Conclusions: Individuals with low European group trend to have bigger sagittal maxillary to those with high European group. Additionally, individuals with high European group trend to have larger component of the vertical mandibular rotation than low European group.
Further studies should include a bigger sample to establish a stronger relationship between Ethnicity and cephalometric landmarks in order to develop cephalometric standards for Antioquian population based on genetic admixture traits.