Variability of facial movements in relation to sexual dimorphism and age: three-dimensional geometric morphometric study.

The aim of this study was to introduce suitable imaging technique and analytical methods for a detailed description of the facial movements in relation to sexual dimorphism and age in adult individuals. Removing of size factor from the analysis, we hypothesised that there will be no significant intersexual difference in facial mobility. We assume facial movements to be more pronounced in the older age category due to increasing the facial surface. We have compared five facial movements - raising eyebrows, closing eyes, pursing of the lips, inflating of the cheeks and smile - in relation to neutral expression of the human face. The material sample comprised three-dimensional facial surface models of healthy adult individuals of the Czech nationality (63 females, 58 males). Methods of geometric morphometry and multivariate statistics were used. Local tissue motion due to facial movements was expressed using colour-coded maps. The movement showing significant intersexual difference was inflating of the cheeks. Ageing in both sexes has significantly influenced the facial mobility on average after 50 years of age. Changes related to senescence have occurred in eye closing, smile and inflating of the cheeks. An enlarged facial surface has been noted in the group of individuals belonging to the older age category, what is probably the result of increased manifestation of skin folds and wrinkles. This is related to the loss of skin elasticity and overall weakening of the underlying muscles, especially in the infraorbital and cheeks area.

Diachronic changes in size and shape of human proximal tibia in Central Europe during the latest 1200 years.

During the past twelve centuries, the stature of Central European inhabitants has increased significantly with corresponding changes in the size of lower limb bones. The aim of our study was to determine whether these changes have occurred strictly in relation to size or if the shape of skeletal structures has been altered simultaneously. Diachronic size and shape changes in the proximal part of tibia in a Central European population (Czech Republic) were studied using geometric morphometrics (principal components analysis, Hotelling's test, linear discriminant analysis). The study sample consisted of 183 three-dimensional (3D) models of adult tibiae dating to the early Middle Ages (N=65), early 20th century (N=60), and from a modern Czech population (N=57). A positive secular trend in size manifested only between the two modern Czech populations (the 20th century vs. the 21st century), a time range shorter than one century. By contrast, landmark-based shape analyses revealed significant differences in tibial morphology over the three periods covered in the study. In particular, progressive changes were observed in the position of tibial tuberosity (shifted medially), the inclination of the line connecting tuberosity with anterior edge of the tibial plateau (sloped down), the reshaping of the lower back condyle boundary (shifted posteriorly), and reshaping of the medial contour of the medial condyle (shifted anteriorly). Changes in the shape of the proximal tibial extremity across the chronologically distinct groups indicated the existence of discreet but convincing microevolutionary trends involving this anatomical structure.

Three-dimensional analysis of palatal shape in patients treated with SARME using traditional and geometric morphometrics.

OBJECTIVES: To demonstrate the advantages of dense surface models in the evaluation of surgical-assisted rapid maxillary expansion's effect (SARME) on palatal morphology. Furthermore, we compared the palatal surface before (T1) and after (T2) therapy with controls. SETTING AND SAMPLE POPULATION: Surgical-assisted rapid maxillary expansion's effect group of 15 adult patients (Le Fort I and midpalatal sagittal osteotomy, hyrax screw) and 50 adult individuals. Patients were treated in General Faculty Hospital, Prague. MATERIALS AND METHODS: Eighty plaster casts were digitized using a three-dimensional laser scanner and evaluated using traditional and geometric morphometrics. RESULTS: An unpaired Student's t-test on the controls and the SARME T1 group revealed significant differences in all width measurements. Between the controls and the SARME T2 group, significant differences were only related to the interdental angle between the first molars and particularly to the palatal height. The most remarkable differences between the pre- and post-treatment palatal morphology were a widening of the dental arch and buccal shift of the lateral teeth associated with apparent flattening of the alveolar crest. CONCLUSIONS: Dense surface model provided descriptive visualization of the treatment effect and was helpful in the evaluation of palatal shape variability including detection of the most difficult patients. Correction of the dental arch width discrepancy by SARME was successfully achieved. After therapy, palatal shape variability of most of the patients was comparable to the variability of the control group.

Development of facial sexual dimorphism in children aged between 12 and 15 years: a three-dimensional longitudinal study.

OBJECTIVES: To evaluate sexual dimorphism of facial form and shape and to describe differences between the average female and male face from 12 to 15 years. SETTING AND SAMPLE POPULATION: Overall 120 facial scans from healthy Caucasian children (17 boys, 13 girls) were longitudinally evaluated over a 4-year period between the ages of 12 and 15 years. MATERIALS AND METHODS: Facial surface scans were obtained using a three-dimensional optical scanner Vectra-3D. Variation in facial shape and form was evaluated using geometric morphometric and statistical methods (DCA, PCA and permutation test). Average faces were superimposed, and the changes were evaluated using colour-coded maps. RESULTS: There were no significant sex differences (p > 0.05) in shape in any age category and no differences in form in the 12- and 13-year-olds, as the female faces were within the area of male variability. From the age of 14, a slight separation occurred, which was statistically confirmed. The differences were mainly associated with size. Generally boys had more prominent eyebrow ridges, more deeply set eyes, a flatter cheek area, and a more prominent nose and chin area. CONCLUSION: The development of facial sexual dimorphism during pubertal growth is connected with ontogenetic allometry.

Surface facial modelling and allometry in relation to sexual dimorphism.

Sexual dimorphism is responsible for a substantial part of human facial variability, the study of which is essential for many scientific fields ranging from evolution to special biomedical topics. Our aim was to analyse the relationship between size variability and shape facial variability of sexual traits in the young adult Central European population and to construct average surface models of adult males and females. The method of geometric morphometrics allowed not only the identification of dimorphic traits, but also the evaluation of static allometry and the visualisation of sexual facial differences. Facial variability in the studied sample was characterised by a strong relationship between facial size and shape of sexual dimorphic traits. Large size of face was associated with facial elongation and vice versa. Regarding shape sexual dimorphic traits, a wide, vaulted and high forehead in combination with a narrow and gracile lower face were typical for females. Variability in shape dimorphic traits was smaller in females compared to males. For female classification, shape sexual dimorphic traits are more important, while for males the stronger association is with face size. Males generally had a closer inter-orbital distance and a deeper position of the eyes in relation to the facial plane, a larger and wider straight nose and nostrils, and more massive lower face. Using pseudo-colour maps to provide a detailed schematic representation of the geometrical differences between the sexes, we attempted to clarify the reasons underlying the development of such differences.

Nearly on-line picosecond streak camera diagnostics of the cw mode-locked YAG laser radiation.

An image-converter streak camera incorporating a TV video-recording system interfaced to a computer HP 2100 was used to record and instantly display the processed shape of a picosecond laser pulse. The output versus input exposure response curve linearity of the whole system was verified over a dynamic range of at least 10. Performance testing of the system was done using a cw mode-locked YAG laser.