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Biomedical subjects

I Kjaer

Publications and source records attributed to I Kjaer.

At least 91 records · Page 5Linked to original sources
PubMed1993

An immunocytochemical study of the innervation of developing human fetal teeth using protein gene product 9.5 (PGP 9.5).

Developing teeth of 32 human fetuses (crown-rump length 11-205 mm) were examined immunohistochemically by antisera to protein gene product 9.5 (PGP 9.5) in an attempt to shed light upon the possible role of innervation in odontogenesis. As a control for the specificity of PGP 9.5 as a neuronal marker, the results were verified by immunocytochemical co-localization in peripheral nerves of neurone-specific enolase, neurofilaments and S-100 protein. The dental follicle received the first nerve fibres in the early cap stage. At this stage, fibroblasts differentiated in the presence of nerve fibres and formed the dental follicle surrounding the developing tooth. In the dental papilla, however, no fibres were demonstrated until the dentine and enamel matrices had formed, about half of the present height of the tooth germ. Most nerve fibres were localized in the basal part of the papilla until the last stage examined and usually followed the blood vessels of the papilla. Thus the effect of innervation on tooth development may be associated with the development of the dental follicle. A novel finding was that functional odontoblasts were not only positive for S-100 but also for PGP 9.5, indicating their neural crest origin.

Antibodies, Monoclonal↗
PubMed1993

Comparison of human dental and craniofacial maturation on prenatal profile radiographs.

The present study reveals new data concerning the prenatal interrelationship between maturation of teeth and basicranial bones. By using radiographs of the mid-sagittal tissue segment of 43 human craniums, the developmental relationship between a well-defined stage of the central maxillary incisor development and the development of the basicranium was determined. Histological controls were performed to verify the radiographic findings. The study shows a close connection between the incisor development and the cranial development. Furthermore, comparisons are performed to the generally used parameters for prenatal growth, i.e. the crown-rump length (CRL) and the gestational age (GA). A thorough understanding of developmental interactions between the teeth and cranium is important for the understanding of normal, as well as pathological craniofacial development, including tooth development.

Embryonic and Fetal Development↗
PubMed1993

Spheno-occipital synchondrosis in three-month-old children with clefts of the lip and palate: a radiographic study.

The literature has been focused on differences in craniofacial form and dimension in cleft lip and palate patients. No attention has been given to possible alterations in the spheno-occipital synchondrosis although the synchondrosis is regarded as an important maturity and growth center. The purpose of the present investigation was to examine if the spheno-occipital synchondrosis in children born with major complete clefts differs on lateral radiographs from that of children born with minor incomplete clefts. Fifty-seven three-month-old children with complete clefts of the lip, alveolus and palate and 42 three-month-old children with minor incomplete clefts of the lip were included in the study. The results of the comparison showed that children with complete major clefts had a broader spheno-occipital synchondrosis compared to children with a minor incomplete cleft of the lip, and that the distance from the superior part of the synchondrosis to the sella point was shorter in children with complete clefts. These findings could be related to a defect or a delay in maturity in the early development of the cartilaginous cranial base in children with major clefts.

Alveolar Process↗
PubMed1993

The human incisal suture and premaxillary area studied on archaeologic material.

The purpose of this study was to investigate the extent of the incisal suture, the size of the premaxillary area, and the developmental status of the dentition. Sixty-three medieval crania were examined: 30 from children and 33 from adults, including 5 cases with tooth deviations. All crania were photographed at a 1:1 scale. From the photographs the size of the premaxilla and the length of the incisal suture were measured. In addition, the spatial conditions in the anterior region were recorded. The study showed that the main closure of the suture takes place shortly after the crowns of the permanent incisors have attained their final width size. The mean size of the premaxillary area was larger in individuals with interincisal spacing and smaller in individuals with crowding when comparing with normal spatial conditions. In the cases of tooth agenesis the premaxillary areas were markedly reduced.

Adult↗
PubMed1992

Human prenatal palatal shelf elevation related to craniofacial skeletal maturation.

Much attention has been focused on the mechanisms responsible for the elevation and fusion of the palatal processes during formation of the secondary palate. In a former publication this closure, defined as fusion of the palatal shelves along their length, was described as occurring at a period in osseous palatal development characterized by incipient ossification of the maxillae and palatine bones, and at a stage in early mandibular development when the mandibular condyle has not developed. The purpose of the present study was to examine the osseous maturation of the cranial base at the time of palatal closure. The investigation was based on 62 human embryos and fetuses, CRL 22-57 mm, and general skeletal hand and foot maturation CNO = 0-0 to CNO = 8-1 (CNO, Composite Number of Ossified bones in hand and foot). From the fetuses, cranial tissue was dissected out and skeletal maturity was determined radiographically according to formerly described skeletal maturity stages in the cranial base. The study revealed that the soft tissue palatal shelves always elevate and fuse along their length at a specific, well-defined stage of maturity in the cranial base. The cranial base development in this stage is characterized by unossified cartilage. This information is essential for understanding abnormal skeletal development of the oral and nasal cavities.

Facial Bones↗
PubMed1991

Tooth and bone development in a Danish medieval mandible with unilateral absence of the mandibular canal.

A Danish anthropological collection of medieval human skeletons excavated in 1986 involves a mandible (No. 212) from an adult female born without the lower alveolar nerve and mandibular canal. It is believed that the defect has resulted in lack of tooth development on the affected side and that the mylohyoid nerve has partially compensated for this defect by development of teeth in localized areas. The defective mandibular dentition has caused a compensatory development of the alveolar process in the maxilla. The missing occlusal support has altered muscular traction on the mandible. This has caused an alteration in mandibular shape. Whether the asymmetric development of the mandible is caused by muscular dysfunction, by failure in angular growth apposition, or by a combination of these factors is discussed. The case presents valuable data in the ongoing discussion about the interaction between nerve tissue and tooth formation and about the interaction between occlusion, jaw morphology, and muscular traction. The study shows how archeological material in an interdisciplinary cooperation between archeological, embryological and orthodontic research can contribute to the clarification of current biological problems.

Alveolar Process↗
PubMed1991

The midline craniofacial skeleton in holoprosencephalic fetuses.

Craniofacial skeletal development in eight human holoprosencephalic fetuses from second trimester abortions were examined by radiography and histology. The whole spectrum of associated facial malformations from anophthalmia through cyclopia, ethmocephaly, cebocephaly, and median cleft lip to short philtrum was represented. Cases with the most severe facial malformations also had the most severely affected facial skeleton. In the facial skeleton, the premaxilla was most often affected; it was absent in seven cases and malformed in the one with only a short philtrum. This and other facial skeletal malformations can be explained as abnormal fusion of the facial bones because of defective development of the nasal cartilage. The occipital bones were normal, but the basicranial skeleton anterior to the spheno-occipital junction was affected in all cases. The findings support the hypothesis that the facial malformations in holoprosencephaly result from disturbance in embryonal life of the mesoderm at the rostral end of the notochord.

Facial Bones↗
PubMed1990

Simple autopsy method for analysis of complex fetal cranial malformations.

A new radiography technique for examining second trimester abortions permits an accurate analysis of growth and maturation of the fetal skull. Reference material for normal development has been previously published. The potential of the method is demonstrated with three examples: thanatophoric dysplasia, Arnold-Chiari malformation, and anencephaly.

Anencephaly↗
PubMed1990

Correlated appearance of ossification and nerve tissue in human fetal jaws.

The factors initiating the onset of desmal jaw formation are not known. The purpose of the present report was to examine the correlation between the appearance of ossification and nerve tissue in human fetal jaws. This was done through elaboration of similarities in occurrence of tissue types at four different sites of initial bone formation in the jaws. Radiological and histochemical methods applied to the jaws of 26 human embryos/fetuses revealed that nerve tissue appeared in the jaws before bone tissue. Early bone formation occurred in close relation to the mandibular nerve, the maxillary nerve, the palatine nerve, and the naso-palatine nerve. It is suggested that the foramina (mental foramen, infraorbital foramen, palatal foramen, and incisive foramen) are the areas of incipient bone formation, and that the sequence in bone formation corresponds to the sequence in the development of nerve fibers from the trigeminal ganglion.

Histocytochemistry↗
PubMed1990

Prenatal human cranial development evaluated on coronal plane radiographs.

The purpose of the present investigation has been to analyse prenatal cranial base development in the coronal plane and to combine the findings with results in former reports on cranial base maturation estimated in the horizontal and sagittal planes. The study is based upon cranial bases of 26 human fetuses from the first half of the prenatal period. Fetal coronal plane cranial base tissue blocks were dissected, radiographed, and sectioned for microscopic examination. Five stages in cranial base development are defined and related to general parameters for fetal size and fetal maturation. Two different maturation patterns were recognized in the sphenoid corpus. Canal structures, remnants of the craniopharyngeal canal, were observed in specimens showing bilateral centers of ossification in the sphenoid corpus. The radiographic method used is easy to record and recommended for diagnosing prenatal and neonatal cranial malformations.

Fetus↗
PubMed1990

Radiographic determination of prenatal basicranial ossification.

In a previous investigation on prenatal development of the human cranial base, the sequence in which the bones develop in the midsagittal region was elucidated. The purpose of the present study was to identify fetal ossification on horizontal plane roentgenograms of the occipital and sphenoid bones in the central part of the cranial base, and establish stages in bone appearance related to general fetal developmental parameters. This study is based upon roentgenograms of the cranial base of 145 human fetuses from the first half of the prenatal period. Two different maturation patterns of the sphenoid bone were observed. The first, most common pattern is characterized by a midsagittal centre of ossification and the second by bilateral centres of ossification in the corpus of the sphenoid bone. These bilateral centres might in some cases be connected by a slight bony bridge. It appears that these different maturation patterns are maintained throughout the period investigated. The material was divided into five well-defined developmental stages for both maturation patterns and general parameters of fetal development. Mapping different aspects of ossification in normal cranial development is necessary for understanding deviations of cranial maturation and growth.

Gestational Age↗
PubMed1990

Ossification of the human fetal basicranium.

Previous investigations of prenatal development of the human cranium have not identified the sequence of its ossification. The purpose of the present study was to elucidate the pattern of skeletal maturity of the cranial bones in the midsagittal region anterior to the foramen magnum. This study is based upon a radiographic and histochemical investigation of midsagittal tissue blocks of the cranial bases of 73 human fetuses derived from the first half of the prenatal period. A marked regularity in the ossification pattern of the bones in the midsagittal part of the human cranium was observed. Ossification starts in the frontal bone. The sequence in which the next bones ossify is occipital bone, basisphenoid bone, presphenoid bone, and ethmoid bone. The material was divided into 7 maturity stages devised for this analysis. The stages were related to general fetal size (crown-rump length) and to general fetal maturation (composite number of ossified bones in hand and foot). Skeletal development of the median part of the human cranium is not strictly correlated with the size or the stage of general maturation of the fetuses. Knowledge of normal skeletal development is necessary for understanding anomalies of development.

Bone Development↗
PubMed1989

Prenatal skeletal maturation of the human maxilla.

Previous investigations on the prenatal development of the human maxilla have focused mainly on the elevation and fusion of the soft tissue palatal shelves. The bony development has received only sporadic attention. The aim of the present investigation was to analyze and set up bony developmental stages in the human maxilla, as knowledge of normal skeletal developmental course, which has never been elucidated, is the prerequisite to understanding the abnormal course of development. The present study was based on a radiographic and histochemical investigation of maxillae from 104 human embryos and fetuses from the first half of the prenatal period. A marked regularity in the maxillary ossification pattern was observed, and consequently seven maturity stages, Max I-Max VII, were described. The material was divided according to these stages and related to general fetal size (crown-rump length) and to general fetal maturation (composite number of ossified bones in hand and foot). The material available did not justify a description of skeletal development of the maxilla as a function of CRL or CNO.

Humans↗
PubMed1989

Human prenatal palatal closure related to skeletal maturity of the jaws.

The purpose of the present study was to elucidate the stages of skeletal maturation of the maxilla and the mandible at the time of soft tissue palatal closure. Similar studies were not found in the literature. This investigation was based on maxillae and mandibles from 19 human embryos/fetuses selected by visual inspection of palatal structures, eight fetuses "just before palatal closure," and 11 fetuses "just after palatal closure." The findings are related to formerly described skeletal developmental stages in the maxilla, to stages in the symphysis menti region, and to development in the mandibular condylar region. The present study revealed that elevation of the palatal shelves takes place at a specific stage of maxillary skeletal maturity (stage Max III), at a time of mandibular development characterized by absence of condylar cartilage and by constancy in symphysis menti maturity (stage SM I). Knowledge of the normal sequence of prenatal skeletal development is considered essential for understanding the abnormal sequence of skeletal development.

Cartilage↗
PubMed1989

Formation and early prenatal location of the human mental foramen.

The formation and early prenatal location of the human mental foramen was investigated on 43 human fetuses. Histochemical methods supplemented by macroscopic visualization were used. Similar studies on the mental foramen were not available in the literature. The study demonstrated constancy in the developmental sequence of the bony structures in the region of the mental foramen. The formation of the mental foramen was described and related to general developmental parameters such as CRL and CNO values (skeletal maturity indexes of the hand and foot). The study indicated that the very early position of the mental foramen was in the region of the interstitial bone between the primary canine and the primary first molar. A positional change in the dorsal direction was described during the first half of the prenatal period.

Age Determination by Skeleton↗
PubMed1980

Development of deciduous mandibular incisors related to developmental stages in the mandible.

On the basis of morphological and histochemical studies of 71 human mandibles from the former half of prenatal life, five stages (D I to D V) in the development of the deciduous mandibular incisors are described. These stages are related partly to general parameters of fetal development, such as M age (menstrual age), CRL (crown-rump length), CNO (composite number of ossified bones in hand and foot) and partly to stages in the skeletal development of the symphysis menti (SM I to SM V). The investigation revealed close relationship between the development of the deciduous mandibular incisors and the skeletal development of the deciduous mandibular incisors and the skeletal development of the mandible in the region of the incisors. No such relationship was found between the development of the deciduous mandibular incisors and general parameters of fetal development.

Fetus↗