Fetal Mandible Research Articles

Topographic and anatomical relationships of the lower jaw and auricle in human prenatal ontogenesis

Aim to describe the topographic and anatomical relationships of the fetal lower jaw and auricle in the mid-gestation period.
 Material and methods. The 110 mandibles of human fetuses of the second trimester were selected for the study and divided into groups by sex and age. The morphological techniques and the method of ultrasound scanning were used to determine the topographic relationships of the lower jaw and the fetal ear, the location of the central part of the auricle relative to the lower jaw (the line connecting the gnathion point and the external occipital protuberance) at different age periods.
 Results. During the mid-gestation period, with the growth of the fetus, the auricle normally shifts upward relative to the mandible. At the beginning of the study period, the auricle is located just below the angle of the lower jaw. Its central part (C) is below the line (AB) connecting the gnathion point and the external occipital protuberance. The perpendicular from the conditional center of the auricle to the line AB is half the diameter of the auricle 3.7 1.1 mm. In the second age group, the auricle is located at the level of the branch and angle of the lower jaw Its conditional center (C) is below the line AB and is of the diameter of the auricle 3.1 0.8 mm. By the end of the mid-gestation period, the auricle is displaced to the level of the processes of the lower jaw above the notch. Its central part is above line AB, the perpendicular from point C to line AB is 6.1 1.4 mm.
 Conclusion. The deviations in the formation of the topographic and anatomical relationships of the lower jaw and auricle of the fetus from 14 to 27 weeks of gestation can be additional criteria for the development of congenital fetal pathology and require the fetoabnormal alertness.

Reference ranges of fetal mandible measurements: Inferior facial angle, jaw index, mandible width/maxilla width ratio and mandible length in Thai fetuses at 15 to 23 weeks of gestation.

ObjectivesTo determine the normal distribution of 1) inferior facial angles (IFA), 2) jaw index, 3) mandible width/maxilla width ratio (MD/MX ratio), and 4) mandible length (ML) in second trimester Thai fetuses.MethodsA prospective study was performed between April 1 and October 31, 2020, at the Maternal-Fetal Medicine Unit of Songklanagarind Hospital. Transabdominal ultrasonography was performed on Thai singleton pregnant women at 150/7 to 236/7 weeks of gestation to measure IFA, jaw index, MD/MX ratio and ML. All women received standard antenatal care and were followed up until delivery. The exclusion criteria were multifetal gestation, congenital anomaly, chromosomal abnormality, fetal growth restriction, abnormal amniotic fluid volume, suspected abnormality of fetal mandible, maxilla or jaws based on the proposed criteria from previous studies and suspected neonatal structural or genetic abnormalities postnatally. Quantile regression was used to estimate changes in the median, 5th and 95th percentiles of each parameter across gestational ages and to generate formulas for predicting the 5th percentile value for each parameter.ResultsThe results of 291 women were analyzed. Scatter plots and reference ranges of each parameter were generated. IFA, jaw index and ML values significantly increased, while the MD/MX ratio value significantly decreased, with increasing gestational age. The formulas calculated for predicting the 5th percentile value for each parameter were IFA = 55.12 + 0.045*(GA in days—136) jaw index = 37.272 + 0.01693*(GA in days—136) MD/MX ratio = exp(0.027–0.00110*(GA in days—136)) ML = 20.83 + 0.243*(GA in days—136).ConclusionsThe reference ranges and formulas to calculate the 5th percentile values of mandible parameters in Thai fetuses were developed.Trial registrationThis study has been reviewed and approved by the Thai Clinical Trials Registry with identification number TCTR20210602003.

Anatomical features of the human fetus mandible

Aim to obtain new data on the anatomy of the mandible of a human fetus aged 1923 weeks.
 Material and methods. The object of the study was 40 mandibles of human fetuses of both sexes aged from 19 to 23 weeks. The morphological method (macromicroscopic preparation; the method of saw cuts according to N.I. Pirogov; production of serial histotopograms) and the method of ultrasound scanning by the device VOLUSONS 10, RAB 6 RS sensor in 2D mode and in the "Skeleton" program (3D mode) were used.
 Results. In fetuses aged 1923 weeks the mandible represents a paired bone connected in the center by a symphysis. According to the shape of the body, it is possible to select wide and short, long and narrow mandibles in a ratio of 2 to 1, respectively 67% and 33%. The length of the alveolar arch is 52.4 5.6 mm (with a range of 45.360.2 mm), the angular width is 23.4 1.7 mm (with a range of 19.027.8 mm). The height of the branch at the cutting level was equal to 6.2 1.4 mm (with a range of 3.69.0 mm). On the anterior surface of the body, one chin opening is determined on both sides, at an average distance of 16.4 mm from the angle of the mandible and at a height of 2.2 mm. On the inner surface of the branch, the opening of the mandible is determined, located at a distance of 3.6 1.1 mm from the angle, 3.2 0.9 mm from the anterior edge of the branch, 4.1 1.2 mm from the posterior edge of the branch. In the second trimester of pregnancy, dental alveoli are determined in the mandibular dental arch of the fetus. Significant sex differences were found for the angle of the mandible (p 0.05). In girls, the angle was 141.1 10.1, in boys 129.5 9.4.
 Conclusion. The mandible of the fetus at the age of 1923 weeks is formed and has fetal characteristics. During this period, no significant bilateral differences were revealed, sexual differences start to form.

Prenatal Diagnosis of Robin Sequence: Sensitivity, Specificity, and Clinical Relevance of an Index for Micrognathia.

Micrognathia in connection with glossoptosis (called Robin sequence) may lead to life-threatening respiratory problems immediately after birth. An objective detection during prenatal routine ultrasound sonography is possible using an index that relates fetal lower jaw length to femur length or gestational age. The aim of this study was to test the method's sensitivity and specificity and to discuss its predictive power concerning neonatal respiratory insufficiency. Patients with subjectively identified suspicious signs in the sagittal profile view were included in the study: Two-dimensional serial ultrasound scans of their fetal mandible were used to measure the lower jaw lengths and compare them to predicted values according to an index, derived from 313 healthy fetuses. Follow-up data provided additional information on the clinical appearance of the newborns. The index showed a high sensitivity: 15 of the 16 cases with a micrognathia were correctly diagnosed (sensitivity of 93.75%). Follow-up data showed that newborns with similar index values differed in terms of their upper airway obstruction and treatment need. Fetal mandibular micrognathia can be objectively evaluated with the help of the index. The method allows an early detection of micrognathia, which helps to take the necessary steps for proper treatment of potential life-threatening respiratory impairment. Observations ranging outside the prediction interval could prompt the ultrasonographer to check for other associated malformations.

First-Trimester Nonvisualization of the Parotid Gland and Aneuploidy in Fetuses With Increased Nuchal Translucency: A Prospective Cohort Study.

Aplasia and hypoplasia of the major salivary glands, particularly the parotid glands, were reported to be associated with trisomy 21. This study aimed to evaluate the value of first-trimester nonvisualization of the parotid gland in a high-risk population of fetuses with increased nuchal translucency (NT). A single-center prospective observational cohort study was conducted. The feasibility of imaging the parotid gland was assessed in 100 sequential cases of routine low-risk NT scans. In a 2-dimensional image in an axial plane at the level of the fetal mandible, the parotid glands appear as bilateral hyperechoic round areas. Cases referred for counseling for an NT measured above the 95th percentile for gestational age were evaluated for visualization of the parotid glands. Prenatal findings were correlated with fetal genetic analysis results. Forty-two cases with increased NT constituted the final study group. Within the group with nonvisualization of the parotid gland, genetic testing revealed 9 cases of trisomy 21, 3 cases of trisomy 18, and 1 case of monosomy X. The sensitivity and specificity of nonvisualization of the parotid gland as a predictor of aneuploidy were 76% and 80%, respectively. The positive likelihood ratio, negative likelihood ratio, and relative risk were 3.82 (95% confidence interval [CI], 1.67-8.74), 0.29 (95% CI, 0.12-0.71), and 4.33 (95% CI, 1.69-11.09; P < .01). The negative predictive value was 95.14%. First-trimester nonvisualization of the parotid gland may constitute a potential method for detection of aneuploid fetuses within a high-risk population.

A case with multiple accessory foramina of mandible in a fetus

It is aimed to better recognize the mandibular variations by understanding the diversity and positions of accessory foramina better. Accessory formations on a full-term fetal mandible dissected for a mandibular study were examined under a microscope. To observe these formations more clearly, they were photographed with the help of a camera and microscope. In one of the mandibles dissected for a fetal mandibular study, a lateral accessory foramen (LAF1) was detected in the right half just near the mental foramen, and also a medial accessory foramen (MAF1) was detected over the mandibular foramen. In the left half, on the lateral surface relative to the mental foramen, one in the medial (LAF3) and one just above it (LAF2), and last one is near to the ramus of mandible (LAF4), three lateral accessory foramina, were detected. Again, a medial accessory foramen just above the left mandibular foramen (MAF3), and another foramen is near to mandibular symphysis (MAF2), also two medial accessory foramina on the lateral surface were detected. Detection and recognition of such variations are quite important for clinicians in the diagnostic methods and prevention of possible surgical complications.

Micrognathia

Micrognathia

Radiological and Microsurgical Anatomy for Variation of the Mandible: Comparative Study of Human and Macaca fascicularis

Recent studies using cone-beam computer tomography (CBCT) have added to our understanding of anatomical variation in the mandible of humans. However, the distribution of nerves cannot be revealed by CBCT. There have been investigations of the distribution of nerves relating to the mandible, but some proposed causes of these variations remain controversial. In this study, we observed a total of 10 sides from five mandibles of Macaca fascicularis of unknown age and sex using CBCT and dissection under stereomicroscopy. Nine of the 10 sides had two mental foramina in each side. Innervation by the mental nerves depended on the locations of those foramina. The long branch to the mandibular angle ran with a branch of the facial artery, which joined the mental artery in all 10 sides. Five specimens had a median perforating canal in the mandibular bone. In addition, a branch of the sublingual artery, which joined with the small branches of the submental artery, entered the mandibular bone from the median lingual foramen. This foramen was located in the lower part of the mandibular symphysis and passed via the median perforating canal to exit from the median labial foramen, also located in the lower part of the mandibular symphysis. We speculate that the median perforating canal of the mandible, rarely found in humans, is the remnant of the feeding artery of the fetal mandible, and in M. fascicularis is seen in all specimens because they have no mental protuberance. Anat Rec, 300:1464-1471, 2017. © 2017 Wiley Periodicals, Inc.

Mandibular lingual canals distribute to the dental crypts in prenatal stage

To describe configurations of human prenatal mandibular, lingual canals using a limited-field cone beam computed tomography (CBCT) to examine their origin and anatomical significance. Nine fetal mandibles were examined using a CBCT. Mandibular maturity was assessed according to the mandibular size measured directly and image findings on development of dental crypts. Mandibular, lingual canals and the related foramina (mandibular, mental, and lingual foramina) were observed on axial, sagittal, and cross-sectional images. The horizontal position of mental and lingual foramina was assessed by direct observation using a loupe. In all nine mandibles, CBCT images depicted three separate mandibular canals, which individually occurred at the ramus area. One was a short canal directly connecting to the permanent molar crypt. The other two showed a parallel course, following the mandibular corpus toward the frontal area; the upper one connected to the mental foramen, and the lower one distributed anterior area of canine and incisor crypts. Lingual foramina were observed bilaterally in eight of nine mandibles, whose horizontal position was lingual against the crypt of deciduous canine. The lingual canals occurred from lingual foramina, and connected to the close deciduous tooth crypt or the mandibular canal distributing in the frontal area. It was suggested human dentition could be developed by plural mandibular and lingual canals.

Accessory foramen in the human mandible: anatomical and clinical considerations

We read with interest the published article ‘Anatomical classification of accessory foramina in human mandibles of adults, infants, and fetuses’ by Przystanska and Bruska (2012). The authors performed a meticulous study of the accessory foramen in the mandible. We wish to share few scientific facts related to the published topic. It is always better to visualize an accessory foramen in a radiograph. The best possible means is to insert a wire and visualize the continuity of the canal. An accessory foramen is meant for passage of the neurovascular structures. It would be better to interpret the concerned neurovascular structures according to the position of the accessory foramen. A past study cut the mandible in the midline and measured the dimensions of the canal under dissecting microscope (Liang et al. 2007). Even though the accessory foramina were discussed, no speculation was made about the blood vessels or nerves traversing it. The authors mentioned in their discussion that the accessory foramen was connected to the mandibular foramen. Radiographic investigations may provide exact evidence continuity of the accessory foramina with the mandibular canal but it is quite difficult to believe such in the absence of radiographic studies. The accessory foramen has also been reported to have continuity with the incisive canal (von Arx et al. 2011). If there is continuity of the accessory foramen with the mandibular canal, one wonders if the mental nerve emerges out through this foramen. This raises serious issues for successful nerve blocks. Previous studies have described consideration of additional locoregional anaesthesia in the case of failed mandibular block anesthesia (von Arx et al. 2011). In the second paragraph of the results section, under the subheading Adult mandibles, it was mentioned that four different types of foramina were found but only three were mentioned in pointwise form. We wonder if this really refers to types of foramina or do the authors mean different positions of the foramina. Contrary to the present findings, past research studies depict the accessory foramen varying according to age and race (Kaufman et al. 2000). Interestingly, an earlier study speculated that eruption of wisdom teeth may require additional neurovascular nourishment (von Arx et al. 2011). The present study should have discussed the eventualities of eruption of wisdom teeth or even additional dental spurs. Calculation of the mean distance of this canal with respect to a bony point may have been more beneficial to maxillofacial surgeons. These may be needed for planning graft implants. We congratulate the authors for their valiant effort, and thank the editors for publishing an interesting topic.

Anatomical classification of accessory foramina in human mandibles of adults, infants, and fetuses

In the past few decades, a number of studies have reported that accessory foramina are located on the internal aspect of the mandible, indicating their potential importance for effective and successful clinical procedures. The aim of this study is to evaluate adult, infantile, and fetal human mandibles for occurrence of accessory foramina. To our knowledge, this is the first time that an attempt has been made to examine their particular co-location using a systematic approach and perspective. A total of 397 human mandibles, including 299 adult, 18 infantile, and 80 fetal, were investigated macroscopically for the frequency, position, and diameter of accessory foramina. In 96 % of investigated adult mandibles, at least one accessory foramen was found. Foramina were located either superior or inferior to the genial tubercle, as well as lateral to the tubercle. Bearing in mind their usual location, four different types of coexistence of foramina were distinguished. Accessory foramina were also present in similar locations in infantile and fetal mandibles. Accessory mandibular foramina are constant structures of human mandible. Their frequency, size, and location vary depending on the type of the foramen. Observations on children and fetal mandibles showed no significant differences in evaluation of accessory foramina, with the exception of lower occurrence in this group of subjects.

Genetic and environmental influence on diabetic rat embryopathy

We assessed genetic and environmental influence on fetal outcome in diabetic rat pregnancy. Crossing normal (N) and manifestly diabetic (MD) Wistar Furth (W) and Sprague-Dawley (L) females with W or L males yielded four different fetal genotypes (WW, LL, WL, and LW) in N or MD rat pregnancies for studies. We also evaluated fetal outcome in litters with enhanced or diminished severity of maternal MD state, denoted MD(+)WL and MD(-)LW. The MDWW litters had less malformations and resorptions (0 and 19%) than the MDLL litters (17 and 30%). The MDWL litters (0 and 8%) were less maldeveloped than the MDLW litters (9 and 22%), whereas the MD(+)WL (3 and 23%) and MD(-)LW (1 and 17%) litters showed increased and decreased dysmorphogenesis (compared with MDWL and MDLW litters). The pregnant MDW rats had lower serum levels of glucose, fructosamine, and branched-chain amino acids than the pregnant MDL rats, whereas the pregnant MD(+)W and MD(-)L rats had levels comparable with those of the MDL and MDW rats, respectively. The 8-iso-PGF2α levels of the malformed MDLW offspring were increased compared with the nonmalformed MDLW offspring. Diabetes decreased fetal heart Ret and increased Bmp-4 gene expression in the MDLW offspring and caused decreased GDNF and Shh expression in the malformed fetal mandible of the MDLW offspring. We conclude that the fetal genome controls the embryonic dysmorphogenesis in diabetic pregnancy by instigating a threshold level for the teratological insult and that the maternal genome controls the teratogenic insult by (dys)regulating the maternal metabolism.

Análise do crescimento das dimensões da mandíbula em diferentes idades fetais

OBJETIVO: verificar se há assimetria de crescimento entre as hemimandíbulas esquerda e direita, durante o 2º e início do 3º trimestre de gestação. MÉTODOS: foram utilizadas 68 hemimandíbulas (34 mandíbulas) de fetos conservados em solução de formalina a 10%, sendo 20 femininos e 14 masculinos, e realizadas as seguintes mensurações: Côndilo-Processo Coronoide (Co-PC), Gônio-Processo Coronoide (Go-PC), Gônio-Gnátio (Go-Gn), Côndilo-Gnátio (Co-Gn), Altura da Sínfise (AS) e Ângulo da Mandíbula (AM). Os dados foram coletados, tabulados e analisados com auxílio do programa SPSS, versão 11.0, 2005, onde foi realizado o estudo One Way Anova para a comparação entre as médias dos valores das medidas anatômicas das hemimandíbulas direita e esquerda, sendo a idade dividida entre segundo trimestre (Período 1: 13-18 semanas e Período 2: 18-24 semanas), e início do terceiro trimestre (Período 3: 24-30 semanas) de gestação. RESULTADOS: houve discreta assimetria no ritmo de crescimento das medidas Go-Gn, Co-PC, Co-Gn, Go-PC e AS, comparando-se os lados direito e esquerdo, entre o 2º e início do 3º trimestre gestacional, apesar de não estatisticamente significativa (p &gt; 0,05). Constatou-se, também, que houve redução da medida AM, com discreta assimetria, no mesmo período pré-natal, sendo estatisticamente significativa (p &lt; 0,05). CONCLUSÃO: não foram observadas diferenças estatísticas significativas quanto ao crescimento das hemimandíbulas direita e esquerda no período estudado. Por outro lado, houve redução da medida do ângulo da mandíbula no mesmo período, apresentando significância estatística.

Fetal micrognathia: almost always an ominous finding

Fetal micrognathia: almost always an ominous finding

Our challenging to understand non-genetic effect in addition to genetic one on dento-craniofacial morphogenesis in spontaneous cleft lip/palate mouse model from the standing point of pediatric dentistry

Summary Cleft lip with or without cleft palate is the most common congenital anomaly in craniofacial complex, which is our target to deepen our understanding toward a molecular mechanism of dento-craniofacial morphogenesis. The hypothesis that the maternal effects in addition to the genetic ones play important roles on the dento-craniofacial morphogenesis in mice has been tested based on each developmental stage. Firstly, the maternal effects on the intrauterine craniofacial development in the mouse fetus were examined by means of embryo transfer technique, skeletal staining and cephalometry, indicating that the maternal effects were one of important factors on the intrauterine craniofacial morphogenesis of CL/Fr mice. Secondly, when the molecular nature of the maternal effects is elucidated, maternally derived growth factors may play important roles on mouse fetus development. Bone morphogenetic protein 4 (BMP4) and epidermal growth factor (EGF) function antagonistically, yet are coupled in the regulation of initial chondrogenesis. Smad1 serves as a point of convergence for the integration of two different growth factor signaling pathways during chondrogenesis in the mouse fetal mandible. Lastly, transforming growth factor-beta3 (TGF-β3) promoted fusion of cleft lip in the mouse fetus through the molecular pathways. In fact, microsurgical repair of cleft lip in the fetus that produced scarless fusion is mediated by TGF-β3 regulation of mesenchymal cell proliferation and migration at the site of repair. In addition, TGF-β3 promoted cell proliferation and angiogenesis in lip mesenchymal tissues. These events lead to enhancement of the lip fusion in the presence of TGF-β3. In neonatal mouse, application of exogenous TGF-β3 to decrease type I collagen accumulation and consequential scar formation provide the opportunities for the clinical augmentation of scar reduction after cleft lip repair. These findings indicate that the environmental factors provided by the dams cannot be ignored in the etiology of a craniofacial anomaly and/or development in the mouse model in addition to genetic ones.

The immunolocalization and possible role of c-Met (MET, hepatic growth factor receptor) in the developing human fetal mandibular condyle

The c-Met system is involved in skeletogenesis and is expressed in the cartilage of growth plates. However, the localization and role of c-Met during endochondral ossification of developing mandibular condyles or during intramembranous ossification has not yet been elucidated. In this study, c-Met was examined immunohistochemically in the mandibles of human fetuses during weeks 9 and 16 of pregnancy. c-Met was immunolocalised in the whole area of the developing mandible, although to different extents. In the intramembranous bone, mesenchymal cells showed a weak immunopositivity. Osteoprogenitor cells demonstrated a moderate immunopositivity for c-Met, while osteoblasts and osteocytes showed a very strong immunolabelling of c-Met. In the developing mandibular condyles, c-Met immunopositivity increased gradually throughout the proliferative layer towards the pre-hypertrophic cell layer, whereas the cells of the hypertrophic layer were weakly immunopositive. These findings have demonstrated, for the first time, the prominent immunolocalization of c-Met in osteogenic and chondrogenic tissues of developing human mandibles, which indicates possible functions for this receptor during mandibular development.

Endochondral ossification is required for haematopoietic stem-cell niche formation

Little is known about the formation of niches, local micro-environments required for stem cell maintenance. Here we develop an in vivo assay for adult hematopoietic stem cell (HSC) niche formation 1-2. With this assay, we identified a population of progenitor cells with surface markers CD45-Tie2-αV+CD105+Thy1.1- (CD105+Thy1-) that when sorted from 15.5 dpc fetal bones (fb) and transplanted under the adult mouse kidney capsule could recruit host-derived blood vessels, produce donor-derived ectopic bones through a cartilage intermediate, and generate a marrow cavity populated by host-derived long term reconstituting HSC (LT-HSC). In contrast, CD45-Tie2-αV+CD105+Thy1+ (CD105+Thy1+) fb progenitors form bone that does not contain a marrow cavity. Suppressing expression of factors involved in endochondral ossification, such as osterix and VEGF, inhibited niche generation 22-24. CD105+Thy1-progenitor populations derived from regions of the fetal mandible or calvaria that do not undergo endochondral ossification formed only bone without marrow in our assay27. Collectively, our data implicates endochondral ossification, bone formation that proceeds through a cartilage intermediate, as a requirement for adult HSC niche formation.

Identification and Isolation of the Hematopoietic Stem Cell Niche Initiating Cell Population

Introduction: Identification and understanding of the cells and processes that can generate, sustain and influence the HSC niche and hematopoiesis are critical for the development of a more comprehensive knowledge of normal hematopoiesis, stem cell homing, trafficking, differentiation and hematopoietic pathology. Growth and renewal in many tissues are initiated by stem cells, supported by the microenvironment (niche) in which they reside. While recent work has begun to describe functional interactions between stem cells and their niches, little is known about the formation of stem cell niches.Methods & Results: We established a functional, in vivo assay (via implantation of cells under the renal capsule) to isolate the determinants of hematopoietic stem cell (HSC) niche formation and activity. Using this novel assay, we show that a population of progenitor cells (CD45−Tie2-aV+CD105+Thy1.1−; CD105+Thy1−) sorted from 15.5 dpc fetal limbs and transplanted under the adult mouse renal capsule recruit host-derived vasculatures in a VEGF dependent manner, produce donor-derived ectopic bones through endochondral ossification, and generate a marrow cavity populated by host-derived long term reconstituting HSC (LT-HSC). In contrast, CD45−Tie2-aV+CD105+Thy1a+ (CD105+Thy1+) progenitors form bone that does not contain a marrow cavity. While analyzing these and other sorted populations, we did not observe any instances where niche was present without bone, suggesting that skeletal progenitors are necessary for initiating an HSC niche but osteoblasts alone cannot initiate and support niche activity. Suppression of factors important for HSC maintenance, such as steel factor (SLF), in progenitor populations prior to transplant did not alter their ability to initiate and support an HSC niche. On the other hand, suppression of factors involved in endochondral ossification, such as osterix and VEGF, inhibited niche generation. Furthermore, CD105+Thy1− progenitor populations derived from regions of the fetal mandible or calvaria that do not undergo endochondral ossification form only bone without marrow in our assay.Conclusions: In addition to identifying the limb-derived skeletal progenitor capable of endochondral ossification involved and the basic mechanisms of HSC niche initiation, our study provides a functional framework by which future studies on HSC-niche interactions at the cellular level can be carried out.

Sonographic measurement of the fetal mandible: standards for normal pregnancy.

Measurements of the fetal mandible were made on 204 women with uncomplicated pregnancies and reliable gestational dates. The measurements were made in the sonographic plane, which included the fetal mandible and the hypopharynx. The antero-posterior and transverse jaw measurements increased with gestational age (p < 0.0001), and correlated well with both the biparietal diameter and femur length (p < 0.0001). Measurements were technically more difficult to obtain during the late third trimester. These standards for fetal jaw measurement may be useful in the sonographic identification of micrognathia.

Radiological trace of mandibular primary growth center in postnatal human mandibles

The mandibular primary growth center (MdPGC) of human fetus was conspicuously defined in the soft X-ray view of fetal mandibles. As the peripheral adaptive growth of mandible advances during the postnatal period, the MdPGC image became overshadowed by condensed cortical bones in soft X-ray view. In this study, we traced a sclerotic sequela of MdPGC during the postnatal period. Panoramic radiograms of 200 adults and soft X-ray views of 30 dried adult mandibles were analyzed by statistical methods. The former clearly showed an MdPGC below the middle portion of apices of canine and first premolar, which was distinguishable from mental foramen, and the latter also showed the MdPGC at the same area as a radiating and condensed radiopaque image, measuring 0.5-1.0 cm in diameter. This MdPGC position was seldom changed in the elderly people, even in the edentulous mandibles. Additionally, in the radiological examination, the benign tumors including odontogenic cysts hardly involved the MdPGC, while the malignant tumors of both primary and metastatic cancer frequently destroyed the MdPGC.