Variation in the cranial base orientation and facial skeleton in dry skulls sampled from three major populations.
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The aim of this study was to analyse the effects of cranial base orientation on the morphology of the craniofacial system in human populations. Three geographically distant populations from Europe (72), Africa (48) and Asia (24) were chosen. Five angular and two linear variables from the cranial base component and six angular and six linear variables from the facial component based on two reference lines of the vertical posterior maxillary and Frankfort horizontal planes were measured. The European sample presented dolichofacial individuals with a larger face height and a smaller face depth derived from a raised cranial base and facial cranium orientation which tended to be similar to the Asian sample. The African sample presented brachyfacial individuals with a reduced face height and a larger face depth as a result of a lowered cranial base and facial cranium orientation. The Asian sample presented dolichofacial individuals with a larger face height and depth due to a raised cranial base and facial cranium orientation. The findings of this study suggest that cranial base orientation and posterior cranial base length appear to be valid discriminating factors between different human populations. (+info)
Craniofacial growth in growth hormone-deficient rats.
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Although supplementation with growth hormone (GH) is an accepted treatment for children who are GH-deficient or very small in stature, its effect on the craniofacial skeleton has been little studied. The goal of this study was to compare the absolute and relative growth of the craniofacial skeleton in GH-deficient dwarf rats to that in wild-type rats of the same strain, using a mixed-longitudinal radiographic design. Lateral and dorsoventral X-rays of the head and hindlimb were obtained weekly in dwarf and wild-type female Lewis rats from 4 to 9 weeks of age (n = 14 for each time interval). The X-rays were scanned, 27 cephalometric points were digitized, and selected linear distances were measured between points. Multilevel statistical procedures were used to model growth changes in different regions of the head. Among craniofacial measures, growth curves of the two groups differed greatly in the magnitude of initial size differences and the effect of GH deficiency on growth velocity. Considerable variation (65-97%) also existed among craniofacial measures with regard to relative maturity (i.e., the percentage of growth completed between the first and last time intervals). The deficiency effect (a quantitative estimate of the extent to which growth velocity was affected by GH) was negatively correlated (r = -0.52, P < 0.01) with relative maturity of a particular measure. The dependence of the GH effect on relative maturity suggests that different craniofacial morphologies may result depending on the timing of GH supplementation therapy. (+info)
Craniofacial skeletal and soft tissue morphology in Icelandic adults.
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The purpose of the study was to describe the craniofacial characteristics of Icelandic adults on lateral skull cephalograms. The material consisted of 155 (47.8%) males and 169 (52.5%) females. The mean ages were 35.5 and 34.2 years, respectively. Twenty-two skeletal reference points and 11 soft tissue points were digitized and processed by standard methods with the Dentofacial Planner computer software program. The 45 variables calculated were both angular and linear. Two-sample t-tests were used to study the differences between sexes. Mandibular prognathism was significantly greater in males (P < or = 0.05), but the inclination of both the upper and lower jaws was greater in females (P < or = 0.01). Linear measurements were usually larger for males. The lips were less protrusive in males (P < or = 0.01), but the thickness was greater compared with females (P < or = 0.001). The nose was significantly more protrusive in males (P < or = 0.001). When the Icelandic sample was compared with closely related ethnic groups, such as the Swedes and the Danes, it was interesting to note that the Icelanders seem to be more like the Swedes than the Danes. (+info)
Dentoskeletal effects and facial profile changes during activator therapy.
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The aim of this retrospective study was to investigate cephalometrically the skeletal, dental, and soft tissue modifications induced by activator treatment in patients with Class II malocclusions caused by mandibular retrognathism. The subjects, all in the mixed dentition, were selected from a single centre and were divided into two groups: 40 patients treated with an incisor double capping activator (20 girls, 20 boys with a mean age of 10 years) and a control group of 30 subjects (15 girls, 15 boys with a mean age of 10 years). The dentoskeletal and aesthetic changes that occurred were compared on lateral cephalograms taken before treatment (T0) and after 18-24 months, when the activator was removed (T1). In the control group the radiographs were obtained before (T0) and after (T1) 21 months (standard deviation +/- 3 months). Activator treatment in these growing patients resulted in a correction of the Class II relationship (ANB -2.14 degrees), a restriction of maxillary growth (SNA -0.5 degrees), an advancement of the mandibular structures (SNB +1.64 degrees, FH--NPg +3.39 degrees; OLp-B +5.17 mm, OLp-Pg +5.14 mm, OLp-Go +2.44 mm), a correction of the overjet (-5.03 mm), an improvement in overbite (-1.17 mm) and uprighting of the maxillary incisors (1--FH -5.64 degrees). The activator appliance was effective in treating growing patients with mandibular deficiency: activator therapy corrected Class II malocclusions by a combination of skeletal and dental changes and improved the soft tissue facial profile. (+info)
p120 catenin is required for morphogenetic movements involved in the formation of the eyes and the craniofacial skeleton in Xenopus.
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During Xenopus development, p120 transcripts are enriched in highly morphogenetic tissues. We addressed the developmental function of p120 by knockdown experiments and by expressing E-cadherin mutants unable to bind p120. This resulted in defective eye formation and provoked malformations in the craniofacial cartilage structures, derivatives of the cranial neural crest cells. Closer inspection showed that p120 depletion impaired evagination of the optic vesicles and migration of cranial neural crest cells from the neural tube into the branchial arches. These morphogenetic processes were also affected by p120-uncoupled cadherins or E-cadherin containing a deletion of the juxtamembrane domain. Irrespective of the manipulation that caused the malformations, coexpression of dominant-negative forms of either Rac1 or LIM kinase rescued the phenotypes. Wild-type RhoA and constitutively active Rho kinase caused partial rescue. Our results indicate that, in contrast to invertebrates, p120 is an essential factor for vertebrate development and an adequate balance between cadherin activity and cytoskeletal condition is critical for correct morphogenetic movements. (+info)
Dental-skeletal dimensions in growing individuals with variations in the lower facial height.
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The dental and skeletal dimensions of individuals with Class I skeletal pattern in puberty were compared. Eighty patients with Class I malocclusion were selected, independent of the vertical relations (overbite) of the incisors. The sample was divided into 3 groups: normal, short and excessive lower anterior face height, based on facial proportions. The dental and skeletal measurements of the 3 groups were compared among themselves. In the angular measurements, the results showed no correlation in the mandibular plane angle. In the linear measurements, the mandibular length was significantly greater in the group of patients with short lower anterior face height, with a positive correlation among the three groups. The dentoalveolar heights of the incisors had a positive correlation among the three groups in relation to the lower anterior face height, showing that they are responsible for its variation. (+info)
Regionalisation of early head ectoderm is regulated by endoderm and prepatterns the orofacial epithelium.
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The oral epithelium becomes regionalised proximodistally early in development, and this is reflected by the spatial expression of signalling molecules such as Fgf8 and Bmp4. This regionalisation is responsible for regulating the spatial expression of genes in the underlying mesenchyme. These genes are required for the spatial patterning of bone, cartilage orofacial development and, in mammals, teeth. The mechanism and timing of this important regionalisation during head epithelium development are not known. Using lipophilic dyes to fate map the oral epithelium in chick embryos, we show that the cells that will occupy the epithelium of the distal and the proximal mandible primordium already occupy different spatial locations in the developing head ectoderm prior to the formation of the first pharyngeal arch and neural crest migration. Moreover, the ectoderm cells fated to become proximal oral epithelium express Fgf8 and this expression requires the presence of endoderm. Thus, the first fundamental patterning process in jaw morphogenesis is controlled by the early separation of specific areas of ectoderm that are regulated by ectoderm-endoderm interactions, and does not involve neural crest cells. (+info)
Neural crest cell plasticity and its limits.
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The neural crest (NC) yields pluripotent cells endowed with migratory properties. They give rise to neurons, glia, melanocytes and endocrine cells, and to diverse 'mesenchymal' derivatives. Experiments in avian embryos have revealed that the differentiation of the NC 'neural' precursors is strongly influenced by environmental cues. The reversibility of differentiated cells (such as melanocytes or glia) to a pluripotent precursor state can even be induced in vitro by a cytokine, endothelin 3. The fate of 'mesenchymal' NC precursors is strongly restricted by Hox gene expression. In this context, however, facial skeleton morphogenesis is under the control of a multistep crosstalk between the epithelia (endoderm and ectoderm) and NC cells. (+info)