ABSTRACT
Current studies on facial growth and development have been largely based on European populations. Less studied are African populations, who because of their distinct genetic makeup and environmental conditions, provide deeper insights into patterns of facial development. Patterns of facial shape development in African populations remain largely uncharacterised. Our study aimed to establish facial growth and development trajectories based on a cohort of 2874 Bantu Africans from Tanzania aged 6-18 years, with particular focus on identifying morphogenetic processes that lead to observed developmental shape changes. Procrustes ANCOVA suggested sexually dimorphic patterns of facial shape development (p = 0.0036). The forehead was relatively contracted during development in both sexes. The glabella region was more anteriorly displaced in females due to expansion in the region laterosuperior to the eyes. Nasal protrusion increased with development, which was found to arise from local expansion in the nasal alae and columella. Local expansion in the upper and lower labial regions resulted in forward displaced lips in both sexes, with the effect more pronounced in males. The mentum was displaced more anteriorly in females due to comparatively more expanded mental regions with development. The lateral facial region corresponding to the underlying body of the mandible were developmentally expanded but were posteriorly positioned due to protrusive growth of surrounding structures. Generalised additive modelling of Procrustes variance suggested that facial variation decreased non-linearly with age (p < 0.05). Relative principal component analysis suggested that variations in facial outline shape were developmentally constrained, whereas nasolabial and mental regions, where developmental changes were significant, became morphologically diversified with development. In contrast to simple descriptive illustration of facial shape development, we gained transformative insights into patterns of facial shape development by analysing morphogenetic processes and variational properties. Our analytical framework is broadly applicable to morphometric studies on ontogenetic shape changes.
ABSTRACT
Developmental changes of facial shape are commonly investigated through geometric morphometrics. A limitation with this approach is the inability to investigate patterns of morphological changes at local scale. This could be addressed through quantifying the deformation required to deform one shape to another. This study aimed to investigate changes in mean, rate and variance of facial shape at local scale using geometric morphometrics through deformation perspective. A total of 2112 Europeans 3 to 40 years old from the three-dimensional Facial Norms project were included. Shape and rate trajectories from partial least-squares regressions revealed that the developmentally protrusive nasal bridge was due to local expansion in surrounding tissues as opposed to shape changes in nasal bridge per se. Local expansion of the supraorbital region, in particular the medial part in males, resulted in the sloping forehead and deep-situated eyes with development. Facial shape variation increased nonlinearly with age (p < 0.05), with features having larger rate of change becoming more developmentally diversified. In summary, our deformation perspective facilitates unravelling morphogenetic processes underlying shape changes. Our extended analytical scope inspires novel measures worthy of consideration while establishing facial growth charts. The analytical framework in this study is broadly applicable for analysis of shape changes in general.
ABSTRACT
INTRODUCTION: Over the past 2 decades in the U.S., the reduced burden and narrowed inequality in oral health among children are in stark contrast with the high burden and widening inequality in adult oral health. This study aimed to explore the burden, trends, and inequalities of untreated caries in permanent teeth in the U.S. during 1990-2019. METHODS: Data on burden of untreated caries in permanent teeth were extracted from the Global Burden of Disease Study 2019. A set of advanced analytical methods were applied to provide an in-depth characterization of the epidemiologic profile of dental caries in the U.S. Analyses were conducted during April 2022-October 2022. RESULTS: In 2019, age-standardized incidence and prevalence of untreated caries in permanent teeth were respectively 39,111.7 (95% uncertainty interval=35,073.0-42,964.9) and 21,722.5 (95% uncertainty interval=18,748.7-25,090.3) per 100,000 person-years. Population growth was the primary driver of the increased caries cases, which contributed 31.3% and 31.0% of the increase in the number of incident and prevalent caries cases, respectively, during 1990-2019. The highest caries burden was noted in Arizona, West Virginia, Michigan, and Pennsylvania. The slope index of inequality remained stable (p=0.076), whereas the relative index of inequality increased significantly (average annual percent change=0.04, p<0.001) in the U.S. The burden of untreated caries in permanent teeth remained significant with a widening cross-state inequality during 1990-2019. CONCLUSIONS: The oral healthcare system in the U.S. needs to prioritize health promotion and prevention with a focus on expanding access, affordability, and equity.
