Sexual dimorphism in frontal bone roundness quantified by a novel 3D-based and landmark-free method.

In this study we present a novel and landmark-free method for quantifying shape differences between male and female frontal bones. CT scans were recorded for 80 male and 80 female Turkish hospital patients, age 25-40. The frontal bones were first isolated from the 3D models by digital cutting along the bordering sutures, and then aligned to a CAD-based sphere. This allowed us to quantify the amount of frontal bone overlapping with the sphere (on average 43.2 ± 6.5% for males and 33.9 ± 6.6% for females, the difference is significant at p<0.0001), and to identify areas of shape difference and deviation from the sphere surface in male and female bones. The larger proportion of spherical frontal bone surface in males challenges the common description of the female forehead as "rounder". Based on the overlap data, we developed discriminant functions able to correctly classify 77.5% of the frontal bone models as male/female. This demonstrates that 3D-based and landmark-free approaches to statistical shape analysis may become a viable alternative to the currently dominating landmark-based approaches for shape investigation.

Variations of midline facial soft tissue thicknesses among three skeletal classes in Central Anatolian adults.

Facial reconstruction is a technique employed in a forensic investigation as a last resort to recreate an individual's facial appearance from his/her skull. Forensic anthropologists or artists use facial soft tissue thickness (FSTT) measurements as a guide in facial reconstructions. The aim of this study was to develop FSTT values for Central Anatolian adults, taking into consideration sex and skeletal classes; first, to achieve better results obtaining the likenesses of deceased individuals in two or three-dimensional forensic facial reconstructions and, second, to compare these values to existing databases. Lateral cephalograms were used to determine FSTT values at 10 midline facial landmarks of 167 adults. Descriptive statistics were calculated for these facial soft tissue thickness values, and these values were compared to those reported in two other comparable databases. The majority of the landmarks showed sex-based differences. Males were found to have significantly larger landmark values than female subjects. These results point not only to the necessity to present data in accordance with sexual dimorphism, but also the need to consider that individuals from different geographical areas have unique facial features and that, as a result, geographical population-specific FSTT values are required.