Quantifying Differences in Skull Morphology Across Population Groups

Objectives:  The objective of this study was to attempt to discern quantifiable differences in skull morphology as it relates to three population groups—Asian, African-American, and Caucasian.  While ethnicity is usually obvious from observing a human face, the hard tissues of the skull across population groups look nearly identical.  However, hard tissues of the skull must have significant variation since soft tissue phenotype across ethnic groups all have an extremely unique appearance.  Methods:  CBCT images of the skull were collected.  The CBCT data analysis was performed using the 3dMD-Vultus software using data from one female Asian, African-American, and Caucasian patient, respectively. The skull was divided into six different sections—maxilla, mandible, zygoma, nose, orbits, and the cranium.  Specific anthropometric landmarks were selected in order to define the borders of the sections in the frontal and sagittal views.  The chosen 120 landmarks where plotted in the x, y, and z planes using sella as the basement reference.  Selected facial proportions in the frontal and sagittal views were determined across the three ethnic groups.  The proportions were compared to find variation across the different skulls to account for expressed morphological variety.  Results:   Caucasians showed a narrower midface with a prominent nasion/glabella area; the cranial base is more superior and set more posteriorly compared to other population groups.  Asians have a wider midface, particularly in the orbital area and more prominent midface; the skull is shorter in the anterior-posterior direction.  From a sagittal view, the Asian skull has a relative flat appearance.  Overall, the proportions of the African-American skull most closely resemble the morphology of the Asian patient.  Conclusion:   Small variations exist in sections of the human facial form. Further work is required to determine the differences in a larger population data set.  Support:NIDCR/T35-HL007473, T-35 Health-Professional Program