The relationship between facial directional asymmetry, handedness, chewing side preference, and eyedness.

We aimed to describe facial directional asymmetry (DA) in individuals with different manifestations of laterality. Due to the overlap between brain and face development, a relationship between the manifestation of brain laterality and DA is hypothesised. These findings could clarify the relationship between the brain and facial phenotype and help to plan facial or oral motor rehabilitation. The DA of 163 healthy individuals was assessed by two complementary 3D methods: landmark and polygonal surface analysis using colour-coded maps. Handedness was assessed using the Edinburgh Handedness Inventory, while chewing side and eye preferences were self-reported. The results showed a similar DA pattern regardless of sex and laterality (the right-sided protrusion of the forehead, nose, lips, and chin) and a slightly curved C-shape of the midline in landmark analysis. A relationship between lateralized behaviours and DA was found only in males, in females the DA pattern was more homogenous. Right-handed individuals and right-side chewers showed a protrusion of the right hemiface. Males, left-handed and left-side chewers, manifested a protrusion of the left lateral hemiface. We suggest that these specific differences in males may be due to their typically higher level of brain asymmetry. No apparent relationship was found between eyedness and DA.

Automatic variable extraction from 3D coxal bone models for sex estimation using the DSP2 method.

Thanks to technical progress and the availability of virtual data, sex estimation methods as part of a biological profile are undergoing an inevitable evolution. Further reductions in subjectivity, but potentially also in measurement errors, can be brought by approaches that automate the extraction of variables. Such automatization also significantly accelerates and facilitates the specialist's work. The aim of this study is (1) to apply a previously proposed algorithm (Kuchar et al. 2021) to automatically extract 10 variables used for the DSP2 sex estimation method, and (2) to test the robustness of the new automatic approach in a current heterogeneous population. For the first aim, we used a sample of 240 3D scans of pelvic bones from the same individuals, which were measured manually for the DSP database. For the second aim a sample of 108 pelvic bones from the New Mexico Decedent Image Database was used. The results showed high agreement between automatic and manual measurements with rTEM below 5% for all dimensions except two. The accuracy of final sex estimates based on all 10 variables was excellent (error rate 0.3%). However, we observed a higher number of undetermined individuals in the Portuguese sample (25% of males) and the New Mexican sample (36.5% of females). In conclusion, the procedure for automatic dimension extraction was successfully applied both to a different type of data and to a heterogeneous population.

Correction: The effect of sex and age on facial shape directional asymmetry in adults: A 3D landmarks-based method study.

[This corrects the article DOI: 10.1371/journal.pone.0288702.].

The effect of sex and age on facial shape directional asymmetry in adults: A 3D landmarks-based method study.

OBJECTIVES: Facial directional asymmetry research, including age-related changes, is crucial for the evaluation of treatment of craniofacial malformations/trauma in orthodontics, facial surgery and forensic sciences. The aim was to describe facial directional asymmetry (DA) in different age categories of adults using 3D methods. According to our hypothesis, facial shape DA (1) depends on sex; (2) differs among age groups; and (3) has wider variability in older age. MATERIAL AND METHODS: A cross-sectional sample of healthy Czech adults without craniofacial trauma or anomalies consisted of 300 3D facial models (151 females). The age-range in the study was between 20-80 years. The shape asymmetry of 28 3D landmarks was evaluated using geometric morphometrics and multivariate statistics. RESULTS: The manifestation of DA was similar in both sexes and in each age category; however, there were some statistical differences. In contrast to the ideal symmetrical face, the mean asymmetrical faces tended to create a slightly bent "C" shape of the midline. Therefore, the upper face was rotated slightly clockwise and the lower face counter-clockwise. The right eye was located slightly higher, with the nasal tip and mandibular region tilting to the left. Sex differences in facial DA were significant before the age of 40. DA was more significant in the youngest males than in the oldest, while the women's DA did not change. CONCLUSIONS: The DA patterns were similar in both sexes and in all age categories (a slightly bent C shape of the midline); however, some significant local differences between male age groups were found. A significantly more pronounced asymmetry compared to other age groups was found only in the youngest males from 20 to 40 years. Moreover, significant sexual dimorphism of DA rapidly decreased after middle age, likely caused by the same age-related changes of the face during aging.