New Insights in Facial Development

A review of genetics of nasal development and morphological variation

The nose is central in the determination of facial esthetics. The variations in its structural characteristics greatly influence the ultimate dentoskeletal positioning at the end of an orthodontic therapy. A careful insight into its developmental etiology will greatly aid the health care professional in identifying patient's real concern about the facial appearance. This in turn will aid in the fabrication of a better treatment plan regarding the end placement goals for the teeth and jaws in all the three dimensions of space. However, this important structure is often missed as a part of the diagnostic and treatment planning regime owing to the lack of meticulous understanding of its developmental etiology by the orthodontists. The development of the nose in the embryo occurs in pre skeletal and skeletal phases by a well-coordinated and regulated interaction of multiple signaling cascades with the crucial importance of each factor in the entire mechanism. The five key factors, which control frontonasal development are sonic hedgehog (SHH), fibroblast growth factors (FGF), transforming growth factor β (TGFβ), wingless (WNT) proteins, and bone morphogenetic protein (BMP). The recent evidence suggests the association of various nasal dimensions and their related syndromes with multiple genes. The revelation of nasal genetic makeup in totality will aid in ascertaining the direction of growth, which will govern our orthodontic treatment results and will also act as a harbinger for potential genetic editing and tissue engineering. This article describes at length the morphological and genetic aspect of nasal growth and development in light of the gender and racial variability along with the emphasis on the importance of knowing these nasal features with regard to diagnosis and treatment planning in orthodontics.

A morphometric analysis of developmental instability in children born with unilateral cleft lip and palate

Unilateral cleft lip and palate (UCLP) is a congenital deformity that occurs due to inadequate merging of the nasal and maxillary prominences during fetal development. Randomly distributed bilateral asymmetries known as fluctuating asymmetry (FA) occur in normally symmetric organisms when evolved mechanisms of developmental stability or equilibrium are disturbed by genetic, environmental, or unknown factors. Here, we hypothesize that facial skeleton FA will be increased in a sample of individuals born with UCLP (n = 24) relative to sex- and age-matched controls (n = 24). To test this hypothesis, 23 anatomical landmarks were measured on individual anonymized cone-beam computerized tomography (CBCT) images in children and adolescents (7-17 years). For each individual, 81 pairs of linear distances were used to estimate FAs across the face. To explore sample variation and statistical differences, a principal components analysis and Euclidean Distance Matrix Analysis multivariate bootstrap approach were carried out. Samples show some separation in multivariate space with 44.44% of FA differences being significantly different. The magnitude of FA was larger in the UCLP sample for every significant measurement. The magnitude of significant FA is highest near regions derived from the maxillary and nasal prominences, such as the nasal aperture. These results are useful for medical and dental practitioners when developing treatment options for children and adolescents with UCLP. Clin. Anat. 32:206-211, 2019. © 2018 Wiley Periodicals, Inc.

Developmental pathways inferred from modularity, morphological integration and fluctuating asymmetry patterns in the human face

Facial asymmetries are usually measured and interpreted as proxies to developmental noise. However, analyses focused on its developmental and genetic architecture are scarce. To advance on this topic, studies based on a comprehensive and simultaneous analysis of modularity, morphological integration and facial asymmetries including both phenotypic and genomic information are needed. Here we explore several modularity hypotheses on a sample of Latin American mestizos, in order to test if modularity and integration patterns differ across several genomic ancestry backgrounds. To do so, 4104 individuals were analyzed using 3D photogrammetry reconstructions and a set of 34 facial landmarks placed on each individual. We found a pattern of modularity and integration that is conserved across sub-samples differing in their genomic ancestry background. Specifically, a signal of modularity based on functional demands and organization of the face is regularly observed across the whole sample. Our results shed more light on previous evidence obtained from Genome Wide Association Studies performed on the same samples, indicating the action of different genomic regions contributing to the expression of the nose and mouth facial phenotypes. Our results also indicate that large samples including phenotypic and genomic metadata enable a better understanding of the developmental and genetic architecture of craniofacial phenotypes.

Association Between Facial Length and Width and Fundamental Frequency

OBJECTIVE

This study aimed to evaluate the association between facial width and length and fundamental frequency (F0) and habitual frequency.

STUDY DESIGN

Prospective cross-sectional study.

SUBJECTS

A total of 50 subjects (35 females;15 males) were included in this study.

METHODS

Lateral and posteroanterior cephalometric measurements included: facial height (N-Me); widths of the maxilla (J-J), mandible (AG-AG), and face (Zyg-Zyg); ratios J-J to AG-AG, N-Me to Zyg-Zyg, and lower face to total face heights. All subjects underwent acoustic analysis using Visi-Pitch IV. Sample was stratified according to age and gender.

RESULTS

In the total group (mean age: 14.19±6.49 years; range 6-35 years), a significantly moderate negative correlation existed between Zyg-Zyg, J-J, and AG-AG, and F0 and habitual pitch. Similarly, N-Me moderately correlated with habitual pitch. In males, there was a significant moderate negative correlation between Zyg-Zyg and J-J, and habitual pitch, and between J-J and F0 (-0.571;p=0.026). In females, a significant moderate correlation existed between Zyg-Zyg and AG-AG, and habitual pitch, and between AG-AG and F0 (-0.347;p=0.041). In the prepubertal group (n=25), a negative moderate correlation occurred between J-J and AG-AG, N-Me and habitual frequency, and between J-J and F0 (-0.407;p=0.043). In the postpubertal group, there was a significant moderate correlation only between AG-AG and F0 (-0.403;p=0.046).

CONCLUSION

Facial length correlates significantly with habitual frequency, and facial width correlates significantly with both F0 and habitual pitch. A larger sample of adult subjects is needed to substantiate this conclusion.