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Background: Thorough understanding of developmental changes of human facial shape is lacking. The present study aimed to evaluate developmental shape changes of facial morphology based on a prospective, population-representative, Chinese cohort in Hong Kong. Methods: A population-representative sample of Chinese in Hong Kong was followed. Serial facial images of over 260 participants were obtained at age 12, 15, and 18 years. Facial landmarks were digitized and the corresponding coordinates were submitted for Generalized Procrustes Analysis. The resultant Procrustes shape coordinates, which captured shape information encoded by the facial landmarks, were then used for statistical shape analyses. Results: Small but significant developmental changes in mean facial shape were observed (p < 0.0001 for all pairwise comparisons). Significant age-related changes in the magnitude of variance of facial shape were also observed (p < 0.05). Phenotypic growth trajectories representing developmental shape changes were similar in size (p > 0.05) between sexes but differed in direction (p < 0.05) in shape space and trajectory shape (p < 0.05). The magnitude of shape differences between sexes remained constant from 12 to 18 years. Results of frontal facial shape analyses after removing the effect of allometry were similar to results obtained before removal of allometry. For lateral facial configurations, allometric trajectories among the age-by-sex groups were similar in slope (p > 0.05) but varied in directions in the multidimensional shape space. Conclusions: Our findings suggested significant age-related changes in facial shape and provided a dynamic view of developmental changes in sexual dimorphism of facial shape. Allometry contributed minimally to developmental changes in frontal facial shape. In addition, the allometric trajectories for lateral facial configurations were similar in rate of shape change but differed in their directions in shape space. [ABSTRACT FROM AUTHOR]

Introduction: Existing studies on facial growth were mostly cross-sectional in nature and only a limited number of facial measurements were investigated. The purposes of this study were to longitudinally investigate facial growth of Chinese in Hong Kong from 12 through 15 to 18 years of age and to compare the magnitude of growth changes between genders. Methods and findings: Standardized frontal and lateral facial photographs were taken from 266 (149 females and 117 males) and 265 (145 females and 120 males) participants, respectively, at all three age levels. Linear and angular measurements, profile inclinations, and proportion indices were recorded. Statistical analyses were performed to investigate growth changes of facial features. Comparisons were made between genders in terms of the magnitude of growth changes from ages 12 to 15, 15 to 18, and 12 to 18 years. For the overall face, all linear measurements increased significantly (p < 0.05) except for height of the lower profile in females (p = 0.069) and width of the face in males (p = 0.648). In both genders, the increase in height of eye fissure was around 10% (p < 0.001). There was significant decrease in nasofrontal angle (p < 0.001) and increase in nasofacial angle (p < 0.001) in both genders and these changes were larger in males. Vermilion-total upper lip height index remained stable in females (p = 0.770) but increased in males (p = 0.020). Nasofrontal angle (effect size: 0.55) and lower vermilion contour index (effect size: 0.59) demonstrated large magnitude of gender difference in the amount of growth changes from 12 to 18 years. Conclusions: Growth changes of facial features and gender differences in the magnitude of facial growth were determined. The findings may benefit different clinical specialties and other nonclinical fields where facial growth are of interest. [ABSTRACT FROM AUTHOR]

Objectives Studies investigating influencing factors of permanent tooth eruption/emergence have primarily focused on anthropometric measurements while less attention has been paid to the effect of perinatal factors. We aimed to explore early factors associated with eruption status of permanent teeth among 12-year-olds through a population-representative prospective cohort. Methods A community sample of Hong Kong children born in 1997 was obtained by random sampling from local secondary schools. Participants' background information including birth characteristics, prenatal and early childhood exposures, family socioeconomic status and medical records was prospectively collected. Clinical examination of tooth emergence was conducted in 2010. Children were divided into complete emergence (of 28 permanent teeth) and partial emergence groups based on clinical examinations. Bivariate analyses were used to assess the association of tooth emergence status with each putative predictor. Unadjusted and adjusted logistic regression models were applied to select the best predictors for tooth emergence status at age 12. Results Complete background information and clinical data were available from 514 children (76.9% of the invited participants). Bivariate analyses showed that the average birthweight in the partial emergence group was significantly lower than the complete emergence group (mean difference 0.2 kg, P = 0.006). The finding was confirmed by logistic regression analyses. In the adjusted regression model, it was found that for every 1 kilogram increase in birthweight, the odds of having partial emergence would be lowered by 0.49 (odds ratio 0.49, P = 0.006). Conclusions Birthweight is associated with status of permanent tooth emergence at 12 years of age, as observed from a population-representative sample of Hong Kong children. [ABSTRACT FROM AUTHOR]

Objectives Epidemiological studies on developmental defects of enamel ( DDE) have focused on its potential contributory factors and prevalence while there is limited evidence on the longitudinal changes in the epidemiological profile of DDE. Thus, the objective of this longitudinal study was to investigate whether any type of DDE changes with time. Methods A total of 668 participants were initially recruited in 2010, and 432 participants were successfully followed up and examined for DDE both at the age of 12 in 2010 and 15 in 2013. The central incisor, lateral incisor and first molar in each quadrant were chosen as index teeth and were examined 'wet' by two trained and calibrated examiners using the modified FDI ( DDE) Index. Results The mouth prevalence and tooth prevalence of 'any defect' showed a significant decrease from 2010 to 2013 ( P < 0.001). This was predominantly due to the decrease in diffuse opacities ( P < 0.001). Significant difference in the distribution of the extent of DDE was also found for diffuse opacities at both the participant and tooth levels irrespective of the types of tooth ( P < 0.0001). Median extent score for diffuse opacities in 2013 was lower than those in 2010 at both participant and tooth level irrespective of the types of tooth ( P < 0.001). Conclusions Diffuse opacities, in terms of prevalence and severity, did fade out over time. The observed overall change in DDE was due to the dominating effect of diffuse opacities over demarcated opacities and hypoplasia. [ABSTRACT FROM AUTHOR]