Cephalometric investigation of craniomaxillofacial structures during the prenatal period: a cadaver study.

INTRODUCTION: We aimed to investigate the morphometric development of the cranial base and its related structures, and their growth rate changes from the ninth gestational week to full term in a large group of human fetuses. METHODS: We selected 203 (109 male, 94 female) fetuses between 9 and 40 weeks of gestation and without any external anomalies. From each fetus, standard lateral and posteroanterior cephalometric images were taken using a dental digital panoramic and cephalometric x-ray machine. Fourteen linear and 9 angular parameters were measured. RESULTS: The cranial base angle showed a statistically significant increase between the groups from only the second to the third trimester periods. The sagittal translation of the maxilla increased during the prenatal period, whereas the mandibular sagittal relation grew at a steady rate. The vertical plane angles of the maxilla and the mandible did not show any significant changes. The maxillary length to mandibular length ratio remained stable. CONCLUSIONS: The cranial base angle increased, especially in the second through the third trimesters. The maxilla and the mandible demonstrated different growth patterns in the sagittal direction. The findings of this study could be a guide for interpreting the relationships among the craniofacial structures.

Ihh signaling regulates mandibular symphysis development and growth.

Symphyseal secondary cartilage is important for mandibular development, but the molecular mechanisms underlying its formation remain largely unknown. Here we asked whether Indian hedgehog (Ihh) regulates symphyseal cartilage development and growth. By embryonic days 16.5 to 18.5, Sox9-expressing chondrocytes formed within condensed Tgfß-1/Runx2-expressing mesenchymal cells at the prospective symphyseal joint site, and established a growth-plate-like structure with distinct Ihh, collagen X, and osteopontin expression patterns. In post-natal life, mesenchymal cells expressing the Ihh receptor Patched1 were present anterior to the Ihh-expressing secondary cartilage, proliferated, differentiated into chondrocytes, and contributed to anterior growth of alveolar bone. In Ihh-null mice, however, symphyseal development was defective, mainly because of enhanced chondrocyte maturation and reduced proliferation of chondroprogenitor cells. Proliferation was partially restored in dual Ihh;Gli3 mutants, suggesting that Gli3 is normally a negative regulator of symphyseal development. Thus, Ihh signaling is essential for symphyseal cartilage development and anterior mandibular growth.

Prenatal assessment of the antero-posterior jaw relationship in human fetuses: from anatomical to ultrasound cephalometric analysis.

OBJECTIVES: We wished to develop an ultrasound cephalometric analysis, particularly of the antero-posterior jaw relationship, to increase the accuracy of prenatal diagnosis of retrognathism during the routine midterm test. METHODS: Anatomical cephalometric analysis was performed in 18 formalin-fixed human fetuses (between 16 and 39 gestational weeks), and ultrasound cephalometry was prospectively carried out in 52 pregnant women (21 to 25 gestational weeks). The same landmarks were used in the anatomical and ultrasound median sagittal planes for comparison. Four cephalometric angles were measured relative to the anterior cranial base: alveolar projection of the maxilla and the mandible, chin projection, and facial angle. The antero-posterior jaw discrepancy was calculated. RESULTS: The projection of the maxilla was similar in the two cephalometric analyses (IC [-3.39, 0.23]), whereas the values of the projection of the mandible were lower in the ultrasound sample. The slope of the regression line of the antero-posterior jaw discrepancy on fetuses' age did not show significant differences (IC [-0.05, 1.54]) between anatomical and ultrasound cephalometry, although a difference of 3.23° ± 0.78° (IC [1.69, 4.77]) was observed. Despite this variability, the projections of mandible and chin were well determined by the projection of the maxilla both in the anatomical and ultrasound sample. CONCLUSIONS: Cephalometric analysis by prenatal sonography can be performed to study the antero-posterior jaw relationship. We think that this procedure could be useful to improve prenatal diagnosis of retrognathism in high-risk pregnancies. Further studies should address the reproducibility and accuracy of such analysis.

Apoptosis as a creative agent of embryonic development of bucca, mentum and nasolacrimal duct. An in vivo study in rats.

INTRODUCTION: For embryonal facial development several fusion processes between different facial prominences are necessary. If fusion fails to appear, various facial clefts may occur, known as median (e.g. lower median cleft lip), oblique (e.g. open nasolacrimal duct) or lateral facial clefts (macrostomia, lateral cleft). MATERIAL AND METHODS: The development of 3 different facial regions (bucca, mentum, and nasolacrimal duct) was examined in rats using serial histological sections on day 13.5 after conception. Common procedures were used (staining for active caspase-3 and for Ki-67) for histological assessment about the role of apoptotic and proliferative processes in the fusion zones of buccal, mental and nasolacrimal areas. RESULTS: Multiple apoptotic events were detected in epithelial cells of the respective regions, the proliferative centers were located in the mesenchymal surroundings of fusion zones. CONCLUSION: A substantial precondition for fusion of facial prominences are proliferative and apoptotic processes in epithelial and mesenchymal cells. Apoptosis contributes to the development of bucca, mentum and the nasolacrimal duct. Absence of apoptoses may be responsible for facial clefts.

Validation of biometric study of fetal mandibles by 3D tomodensitometric images.

We carried out a biometric study of the mandible during the last two trimesters of fetal life using three-dimensional tomodensitometric images. We first validated the method of fetal mandible measurement from three-dimensional reconstructions, and then compared these measurements with direct measurements on dissected mandibles. Thanks to the biometric technique on three-dimensional images, dissection of mandibles is no longer necessary, allowing the material to be conserved for later studies. Tomodensitometric images of the whole fetal skull can be obtained in 10 minutes, a much shorter time than that required for dissection of the fetal mandible. Another major advantage is the possibility of computerized image storage, which allows subsequent studies on the same material, its observation and manipulation as well as exchange of findings with the research community, with no risk of damage to the original material.

Nomograms for the sonographic measurement of the fetal philtrum and chin.

OBJECTIVE: To generate nomograms for the sonographic measurement of the fetal philtrum and chin during pregnancy. DESIGN: A prospective, cross-sectional study in normal singleton pregnancies. SUBJECTS: One hundred and fifty-three fetuses between 13 and 42 weeks of gestation were studied. METHODS: The philtrum was measured from the base of the columella to the upper lip. The chin was measured from the tip of the lower lip to the skin under the lower tip of the mandible. Predictive models were evaluated to generate graphic description of the 5th, 50th and 95th centiles for the fetal philtrum and chin. RESULTS: Fetal philtrum length increased with gestational age. The regression equation for the philtrum length (y) according to gestational age in weeks (x) is best predicted by the S-curve (Gompertz) model, as described by the following equation: y = exp(a + b/x), where a = 2.778577, and b = -23.476723 (R(2) = 85.3%, p < 0.0001). The fetal chin length increased with gestational age. The regression equation for the mean chin length (y) according to gestational age in weeks (x) is best predicted by the S-curve model as described in the following equation. y = exp(a + b/x), where a = 3.7922, b = -28.043, (R(2) = 89.0%, p < 0.0001). CONCLUSIONS: The nomograms generated in this study for the fetal philtrum and chin during pregnancy can be used in confirming subjective impression of facial dysmorphism.

Bone remodeling during prenatal morphogenesis of the human mental foramen.

From a morphogenetic point of view, the mental foramen of the mandible is a highly suitable model to study the interactions of different tissues such as nerves, vessels, mesenchymal cells, cartilage, and bone. In previous work, we provided a three-dimensional description of the mental foramen at different developmental stages, and now we complement those studies with a three-dimensional visualization of different bone remodeling activities around the mental foramen. Histological serial sections of human embryos and fetuses, ranging in size from 25 to 117 mm crown-rump-length (CRL), were used to characterize the bone remodeling activity (apposition, inactivity, and resorption). We quantified and reconstructed this activity in three dimensions, and included information on the spatial relationship of the nerves, vessels, and dental primordia. In general, the mandible showed strong apposition at its outer surfaces. The brim of the mental foramen, however, displayed changing remodeling activity at different stages. In the depth of the bony gutter, which provides space for the nerve and the blood vessels, we found bone resorption beneath the inferior alveolar vein. Bone was also resorbed in proximity to the dental primordia. In future studies, we will relate gene expression data to these morphological findings in order to identify molecular mechanisms that regulate this complex system.

Assessment of the facial features and chin development of fetuses with use of serial three-dimensional sonography and the mandibular size monogram in a Chinese population.

OBJECTIVE: Our purpose was to evaluate whether the application of serial three-dimensional (3D) sonography and the mandibular size monogram can allow observation of dynamic changes in facial features, as well as chin development in utero. STUDY DESIGN: The mandibular size monogram has been established through a cross-sectional study involving 183 fetal images. The serial changes of facial features and chin development are assessed in a cohort study involving 40 patients. RESULTS: The monogram reveals that the Biparietal distance (BPD)/Mandibular body length (MBL) ratio is gradually decreased with the advance of gestational age. The cohort study conducted with serial 3D sonography shows the same tendency. Both the images and the results of paired-samples t test (P<.001) statistical analysis suggest that the fetuses develop wider chins and broader facial features in later weeks. CONCLUSIONS: The serial 3D sonography and mandibular size monogram display disproportionate growth of the fetal head and chin that leads to changes in facial features in late gestation. This fact must be considered when we evaluate fetuses at risk for development of micrognathia.

Prenatal morphogenesis of the human mental foramen.

The mental foramen, at first glance, merely looks like a hole where the mental nerve and the vascular bundle runs through. From a morphogenetic point of view, however, the mental foramen is a suitable model to study the development of a structure where different components are involved. To understand this developmental process, a three-dimensional description at different developmental stages first has to be given. From histological serial sections of human embryos and fetuses, ranging in size from 19 to 117 mm crown rump length (CRL), three-dimensional reconstructions of the foraminar regions were made. Outline and form of the developing foramen, size, course of the mental nerve and the adjacent blood vessels could be shown in detail. In this way, the formation of these structures became concrete in three dimensions. In the future, to understand the mechanisms regulating this complex system, where a nerve and blood vessels became successively surrounded by bone, molecular biological data have to be correlated with morphological findings.

The human chin revisited: what is it and who has it?

Although the presence of a "chin" has long been recognized as unique to Homo sapiens among mammals, both the ontogeny and the morphological details of this structure have been largely overlooked. Here we point out the essential features of symphyseal morphology in H. sapiens, which are present and well-defined in the fetus at least as early as the fifth gestational month. Differences among adults in expression of these structures, particularly in the prominence of the mental tuberosity, are developmental epiphenomena and serve to emphasize the importance of studying this region in juveniles whenever possible. A survey of various middle to late Pleistocene fossil hominids for which juveniles are known reveals that these features are present in some late Pleistocene specimens assigned to H. sapiens, but not in all of the presumed anatomically modern H. sapiens (i.e., Qafzeh 8, 9, and 11). The adult specimens from Skhul, as well as the adult Qafzeh 7 specimen, are similarly distinctive in symphyseal morphology. Neanderthals are quite variable in their own right, and they as well as other middle to late Pleistocene fossils lack the symphyseal features of H. sapiens. Some of the latter are, however, seen in the Tighenif (Ternifine) mandibles.

Mandibular growth rates in human fetal development.

A morphometric analysis of changing proportions in the developing mandible was undertaken in 18 human embryos and fetuses of both sexes (developmental age from 8 to 14 weeks, crown-rump length, CRL, from 34 to 110 mm), previously cleared and stained with a specific method for bone (alizarin red S). Reference points were located on the mandible, i.e. condylar process (Pcl), coronoid process (Pco), gnathion (GN), gonion (GO), superior symphyseal point (SSP), for measuring linear dimensions, i.e. Pcl-GN, Pcl-Pco, Pco-GN, GO-GN, SSP-GN. The gonial (Pcl-GO-GN) and the (Pcl-GN-Pcl) angles were also measured. All linear dimensions were correlated with the CRL by bivariate allometry (1n y = 1n a+b 1n x): they all grew with positive allometry, except GO-GN with isometry. The mandibular ramus grew relatively faster than the body, both in length and height, and the greatest growth rate was found for ramus height. The relation between mandibular shape and the craniofacial structures was investigated using scale drawings obtained from photographs of fetal skulls in lateral view. In the youngest fetuses the mandible was prognathic, then became retrognathic. During the period investigated the zygomatic process and squama of the temporal bone were in a lower and more inclined position in relation to the transverse plane passing through the zygomatic arch than in the newborn and adult. This study identifies parameters fitting changing trends in height, length and shape of the human mandible during the prenatal period (8-14 weeks); moreover, it emphasizes that the mandibular growth patterns differ significantly from those of successive development periods.

[A histological and histomorphometric study of the mandibular condyle during prenatal growth of the human mandible]. / Etude histologique et histomorphométrique du condyle mandibulaire durant la croissance prénatale de la mandibule humaine.

There is still some controversy on condylar cartilage growth capacity, whether it is similar or not to long bones growth cartilage. Recently it has been set that human tibial proximal growth decreases gradually throughout the second half of pregnancy period. The aim of this study is to determine whether changes are produced within mandibular condylar cartilage during fetal period are similar or not those that take place in growth platform. Lateral X-rays from the right half of the mandible of 19 human foetus between 18 and 41 weeks had been obtained. Total mandibular length, corpus length, ramus length and gonial angle were measured. A hystological condylar study was made, recording its thickness from sagittal sections of the central condylar area. Total mandibular length as well as corpus and ramus length progressively increased during studied period, existing high correlation between those parameters and gestational age and weight. Gonial angle decreases in studied period. Changes in condylar thickness were correlated neither with pregnancy age nor with fetal weight or X-rays mandibular parameters. These outcomes show that changes in mandibular condyle are not similar to those produced in tibial growth proximal platform and suggest condylar modifications could be more related to local factors than with general body growth mechanisms.

Sectores mandibulares de interés especial en la ortopedia funcional / Mandibular sectors of special interest in functional orthopedics

Se realizan estudios pre y postnatales, lo cual permite anexar y reforzar conceptos emitidos en investigaciones previas. Se destaca la importancia del tejido conjuntivo de la región anterior (sinfisiaria, y de un sector del cóndilo mandibular. Ambos son fundamentales en la vida prenatal, caracterizándose por su potencial generador, y siguen siendo activos después del nacimiento. Especialmente a nivel condíleo, se enfatiza en el tejido que se desliza desde el menisco, desplazándose por debajo del estrato externo o de recubrimiento. Ese tejido conjuntivo vascularizado, que en prenatales merece elnombre de mesenquimático, difiere de los estratos vecinos por su estructura, apetencia tintorial y vascularización. Se invagina e introduce en el cartílago bajo forma de columnas. Estas proporcionan nutrición a la vez que generan nuevo tejido. En prenatales, dichas columnas atraviesan la línea de erosión y se vuelcan en la zona subcondral. En postnatales se desplazan a través del cartílago y del hueso, volcándose en la médula ósea. También a esas edades es generador tisular. Se relacionan con todos los estratos condilares y con estructuras extracondíleas. Se piensa que las fuerzas ejercidas en algunos sectores del sistema estomatognático repercuten en el tejido conjuntivo vascularizado, dadas las relaciones mencionadas. Este, como consecuencia, puede generar tejidos y por lo tanto modificar distintas estructuras

Sectores mandibulares de interés especial en la ortopedia funcional / Mandibular sectors of special interest in functional orthopedics

Se realizan estudios pre y postnatales, lo cual permite anexar y reforzar conceptos emitidos en investigaciones previas. Se destaca la importancia del tejido conjuntivo de la región anterior (sinfisiaria, y de un sector del cóndilo mandibular. Ambos son fundamentales en la vida prenatal, caracterizándose por su potencial generador, y siguen siendo activos después del nacimiento. Especialmente a nivel condíleo, se enfatiza en el tejido que se desliza desde el menisco, desplazándose por debajo del estrato externo o de recubrimiento. Ese tejido conjuntivo vascularizado, que en prenatales merece elnombre de mesenquimático, difiere de los estratos vecinos por su estructura, apetencia tintorial y vascularización. Se invagina e introduce en el cartílago bajo forma de columnas. Estas proporcionan nutrición a la vez que generan nuevo tejido. En prenatales, dichas columnas atraviesan la línea de erosión y se vuelcan en la zona subcondral. En postnatales se desplazan a través del cartílago y del hueso, volcándose en la médula ósea. También a esas edades es generador tisular. Se relacionan con todos los estratos condilares y con estructuras extracondíleas. Se piensa que las fuerzas ejercidas en algunos sectores del sistema estomatognático repercuten en el tejido conjuntivo vascularizado, dadas las relaciones mencionadas. Este, como consecuencia, puede generar tejidos y por lo tanto modificar distintas estructuras (AU)

Growth and development of human adipose tissue during early gestation.

805 normal-for-age human embryos and fetuses were used to study early prenatal fat development. The investigation included observations on stages of fat morphogenesis at the light microscopic level and computerized image analyses of fat lobule size and number. The buccal fat pad was selected as a model system for the analyses. Fat tissue differentiates between the 14th and the 16th weeks: there are five morphogenic phases in adipose tissue formation, strongly associated with the formation of blood vessels. Fat lobules are the earliest structures to be identified before typical vacuolated fat cells appear. Concerning fat lobule size and number, we show that after the 23rd week the total number of fat lobules remains approximately constant, while from the 23rd to 29th week the growth of adipose tissue is determined mainly by an increase in size of the lobules. These results suggest that the 14th through the 23rd week is a sensitive period in fat lobule development, and that disturbances of normal adipogenesis during this period may play a role in the etiology of obesity in later life.

Histochemical investigations on the symphysis menti in the human fetus related to fetal skeletal maturation in the hand and foot.

Histochemical investigations on the symphysis menti region were performed on 72 human embryos and fetuses of crown-rump lengths (CRL) ranging from 16 to 162 mm, presenting skeletal maturity indices (CNO = composite number of ossified bones in the hand and foot) ranging from 0-0 to 19-11. The symphysis menti region is described in five developmental stages according to morphology and histochemical reactions at the interzone, enchondral bone formation, and Meckel's cartilage. The stages are described according to histochemical reactions for glycosaminoglucuronoglycans, collagen, glycogen, alkaline and acid phosphatase, and non-specific AS esterase. Silver impregnation followed by X-ray and histochemical control for Ca++ deposits supplemented the study. Special attention was paid to a fusion of the bilateral Meckel's cartilages in the midline characteristic of stage II. This is a finding not previously recorded in human fetuses. It is suggested to designate this fusion 'the rostral connection'. Histochemically, the fusion appeared as ordinary cartilage matrix (chondroitin-4- and/or-6-sulphate). The absence of a rostral connection characteristic of stage III is discussed. On the basis of reactions for glycosaminoglycans and activity of hydrolytic enzymes, the symphysis is characterized as a growth zone, active in mandibular growth in width as well as in length, during the first half of the prenatal period. The material available did not justify a description of skeletal development in the symphysis menti as a function of CRL, of skeletal maturation in the hand and foot, or as a function of a combination of these parameters.