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PubMed1979

[Injuries to the facial portion of the skull and their late effects in children and juveniles - a 10-year analysis (author's transl)].

A 10-year analysis comprising a total of 534 patients was used to study the histories of 192 puerile and juvenile patients with maxillofacial injuries. The proportion of children up to ten and fifteen years of age was 11.4 percent and 16.1 percent, respectively. Clinical and roentgenological reexaminations could be made of 139 patients. Typical fracture localizations and the frequency of late effects observed in the facial skeleton and dental system are discussed. It was possible for late damage to former tooth germs in the cleft of fracture to be observed in every second patient. Disturbances of growth after fractures of the body of mandible and the mid-facial skeleton were not noted. Among 33 patients with temporomandibular fractures, there were observed 5 cases showing different degrees of disturbed growth. The therapeutic approach chosen according to age and localization of fracture is described in detail.

Adolescent↗
PubMed1995

Expression of basement membrane type IV collagen and type IV collagenases (MMP-2 and MMP-9) in human fetal teeth.

Formation and degradation of dental basement membrane (BM) are important for tooth development. Data on the expression of genes for type IV collagen (the major structural component of the BM) and type IV collagenases [MMP-2 (72 kDa) and MMP-9 (92 kDa)], enzymes that degrade type IV collagen during human tooth development, are lacking. We studied expression of type IV collagen and the MMP-2 and MMP-9 in human fetal teeth (from the 13th to the 20th gestational weeks, covering cap stage through early hard tissue formation). During cap and bell stages, in situ hybridization located transcripts for alpha 1 type IV collagen chain in the fibroblasts surrounding the enamel organ. No alpha 1 type IV collagen chain mRNA was detected in tooth germ epithelium or dental papilla. However, type IV collagen immunoreactivity was observed in BM underlying the dental epithelium up to the appositional stage. Transcripts for MMP-2 were located mostly in the cells of the dental papilla and follicle. Transient expression of MMP-2 mRNA was observed in the inner enamel epithelium of late cap/early bell-stage teeth. During early apposition, a high level of MMP-2 was confined to secretory odontoblasts. Transcripts for MMP-9 were detected by the sensitive reverse-transcription polymerase chain reaction (RT-PCR) in developing teeth. Thus, in dental BM, alpha 1 type IV collagen chain may be of mesenchymal cell origin. Further, MMP-2 but not MMP-9 may participate in remodeling and degradation of BM during human tooth morphogenesis.

Antisense Elements (Genetics)↗
PubMed1999

Disturbances of palatogenesis and their prophylaxis in animal experiments.

The goal of this study using experimental animals was to induce disturbances of palatogenesis which are comparable to human maxillary clefts. Simultaneously, an in vivo method of testing presumed antiteratogenic substances is presented. 13 gravid Wistar rats bearing 98 fetuses received 200 mg/kg of procarbazine on day 14 post conception (p. c.) to induce malformations. 7 of these gravid animals, bearing 48 fetuses, additionally received 200 mg/kg thiamine daily from day 13-19 p. c. to prevent malformations. On day 20 p. c., the fetuses were teratologically screened: all fetuses were externally examined, the skeletons of 1/3 were visualized using cartilage/bone staining methods, and the heads of 2/3 were histologically examined in 24 sequential frontal sections. At birth, the procarbazine-damaged fetuses exhibited a high rate of cleft palate, primarily involving the secondary palate (94%), which was accompanied by retardation and delayed ossification of the viscerocranium. 66% of the fetuses showed pronounced brachygenia. The disturbances of palatogenesis were frequently accompanied by disturbed odontogenesis, which chiefly manifested itself near the cleft of the frontal maxilla as a reduction in size (63%), retardation (38%) or absence (31%) of the tooth germ. In the trial group additionally treated with thiamine, the findings did not differ significantly from these. The animal model presented here proved suitable for studying palatogenesis and localization-specific testing of substances presumed to have antiteratogenic effects. A prophylactic effect of thiamine initially tested as a highly-dosed monotherapy was not verifiable.

Abnormalities, Drug-Induced↗
PubMed1975

[Odontogenesis, organogenic model using teratomas].

The study of odontogenesis in teratomas, leads to the following observations. Conspicuous odontogenic fields are present in the vicinity of pluri-differentiated cystic structures. Tooth germs are connected to the walls of the cysts by an anastomosed dental laminar. The teeth developing in teratoma are not comparable to the normal process which is harmonized when the formation and the distribution of the various parts are concerned. They are deformed in appearance but not in the same way as the classic genetic malformations. The origin of both epithelial and mesenchymal parts is still not completely understood.

Adult↗
PubMed1978

Fine structure of the human secretory ameloblast.

The fine structure of secretory ameloblasts in primary tooth germs from a human fetus was investigated. Various aldehyde fixatives produced varying qualities of preservation. The morphology of the best preserved ameloblasts differed from that earlier described, mainly in the following respects: the rough endoplasmic cisternae were lamellated and regularly arranged, the mitochondria were of regular shape and size, and the ground substance was dense and homogenous. The extensive Golgi complexes, the mitochondria and the rough endoplasmic cisternae in the apical (distal) part of the ameloblast were longitudinally arranged.

Ameloblasts↗
PubMed1981

Distribution of blood group antigens A, B and H in human fetal oral mucosal and odontogenic epithelium.

The distribution of blood group antigens A, B and H was examined in human fetal oral mucosal and odontogenic epithelium. Tissue from 19 fetuses with crown-rump lengths of 57 mm to 189 mm, corresponding to a fertilization age of 10-20 weeks, was included in the study. The distribution of blood group antigens was studied by immunofluorescence methods on tissue sections. Cell membrane bound blood group antigen A or B was demonstrated in the oral mucosal epithelium of 10 fetuses whereas blood group antigen H was found in all fetuses. All the epithelial cell layers of the tooth germs were devoid of the blood group antigens A, b and H independent of the age of the fetus. The blood group antigens A, B and H were located on the cell membranes of the upper cell layers of the oral epithelium, whereas the basal cells showed no reaction even in the youngest fetuses. Following the differentiation of the epithelial cells, changes were seen in the distribution of the blood group antigens.

ABO Blood-Group System↗
PubMed1999

An immunocytochemical study of amelogenin proteins in the developing tooth enamel of the gar-pike, Lepisosteus oculatus (Holostei, Actinopterygii).

Previous studies have demonstrated the morphological similarity of the enamel-like layer found in the teeth of the coelacanth, lungfish and gar-pike to the enamel of tetrapods. In order to clarify the phylogenetic continuity between both structures, tooth germs of the gar-pike were immunocytochemically studied using an anti-bovine amelogenin polyclonal antibody. Intense immunoreaction was shown over the enamel-like matrix layer. Certain cell organelles associated with the secretory pathway of the ameloblasts were recognized as immunoreactive. These results indicate that the enamel-like layer of the gar-pike is a tissue homologous with the mammalian enamel because both possess a common, amelogenin-like substance.

Amelogenin↗
PubMed2004

New cellular models for tracking the odontoblast phenotype.

Odontoblasts and osteoblasts differ functionally and histologically. Because of their close relationship, mesenchymal cells derived from teeth and bone are difficult to distinguish ex vivo. Indeed, the main non-collagenous components of the odontoblastic extracellular matrix, dentin sialoprotein (DSP) or dentin matrix protein 1 (DMP1), have also been detected in osteoblasts. The need to develop cellular models of odontoblast differentiation and to identify markers specific for the odontoblast lineage, has led us to establish clonal cell lines from tooth germs of day 18 mouse embryos transgenic for an adenovirus-SV40 recombinant plasmid. In this study, we analyzed the phenotypes of three independent clones by RT-PCR and Western blot. These clones synthesised DSP, DMP1 and other extracellular matrix proteins typical of the odontoblast and are therefore likely to be derived from the pulp. Transcripts encoding a set of homeobox proteins involved in craniofacial development, such as Pax9, Msx1, Cbfa1, Dlx2 and 5 were also expressed albeit at a different level. These features of the pulpal clones are shared by the C1 mesodermal cells that are capable of differentiating along osteogenic, chondrogenic or adipogenic lineages In contrast, transcripts for two LIM-domain homeobox family genes (Lhx6 and Lhx7) were only detected in the dental clones. Since these genes are preferentially expressed in the mesenchyme of the developing tooth, this suggests that our transgenic-derived cell lines retain intrinsic properties of odontoblastic cells. They may help to characterise genes specifying the odontoblast phenotype and the signalling pathways underlying odontoblast differentiation.

Adenoviridae↗
PubMed2004

Effects of dexamethasone, vitamin A and vitamin D3 on DSP-PP mRNA expression in rat tooth organ culture.

Vitamin A, 1,25-dihydroxyvitamin D3 and dexamethasone are well-characterized hydrophobic molecules whose biological actions are mediated via different members of the nuclear hormone receptor family. We report here their actions on tooth formation at the molecular level. We have tested the effects of these compounds on osteopontin (OPN), dentin sialoprotein (DSP-PP), and collagen type I expression in pre-mineralization and mineralization stage rat tooth organ cultures which mirror in vivo developmental patterns. These proteins are all believed to participate in the mineralization of dentin. 1,25-Dihydroxyvitamin D3 up-regulated OPN, but had no effect on DSP-PP mRNA expression. Vitamin A up-regulated DSP-PP expression as did dexamethasone. Dexamethasone also up-regulated collagen type I expression. Our results suggest that 1,25-dihydroxyvitamin D3 does not modulate dentin mineralization by directly affecting DSP-PP expression. Vitamin A likely contributes to dentin mineralization by up-regulating DSP-PP expression. Finally, the up-regulation of DSP-PP expression in tooth germ cultures treated with dexamethasone suggests that its application to patient's dental pulp might promote increased extracellular matrix synthesis and mineralization in the pulp and may explain the narrowing of the dental pulp cavity in patients undergoing long-term dexamethasone administration.

Animals↗
PubMed1976

Differentiation of odontogenic tissues in organ culture.

Molar tooth germs from 17-d-old mouse embryos were cultivated in a Trowell-type culture, and different culture media were tested for their ability to support enamel formation. The medium which allowed secretion of considerable amounts of enamel matrix by ameloblasts consisted of BGJb medium supplemented with 20% horse serum, 10% chick embryo extract and 0.9 mM ascorbic acid. At the onset of culture the teeth were in the early bell stage. After 2 weeks of cultivation both odontoblasts and ameloblasts had differentiated, and considerable amounts of predentin and enamel matrix had been secreted. Similar development was also seen in teeth which had been enzymatically separated into the mesenchymal dental papilla and epithelial enamal organ and subsequently recombined in vitro. This method allows good differentiation of odontogenic tissues, and is considered suitable for further studies of tissue interactions in the tooth rudiment.

Animals↗
PubMed1994

Ultrastructural studies and immunolocalization of enamel proteins in rodent secretory stage ameloblasts processed by various cryofixation methods.

BACKGROUND: Cryofixation rapidly immobilizes cell and tissue components in their native state, thereby resulting in an ultrastructural preservation very close to the living situation. We have applied this approach to examine the morphology of secretory stage ameloblasts and the distribution of enamel proteins in these cells. METHODS: Molar and incisor tooth germs from newborn mice and/or rats were quickly dissected and divided into segments. The segments were then rapidly frozen using slam, plunge or pressure freezing, freeze-substituted and embedded in Epon. In addition, incisors from older rats were chemically fixed by vascular perfusion and also dehydrated by freeze-substitution. RESULTS: Well-preserved ameloblasts were obtained with all four tissue processing methods. However, slam freezing often showed mechanical damage to the ameloblasts, particularly at the level of the distal portion of Tomes' processes which appeared severed or distorted. Plunging into liquid nitrogen-cooled liquid propane resulted in comparatively less tissue distortion. High pressure freezing gave a relatively higher yield of well-preserved specimens, although displacement of organelles in ameloblasts was sometimes observed, probably resulting from hydrostatic pressure. Minimal ice crystal and mechanical damage was observed in chemically fixed tooth samples processed by freeze-substitution since such specimens are cryoprotected and their examination is not restricted to a surface layer. With all of the above cryopreparation methods, the ultrastructure of well-preserved ameloblasts was, in general, similar to that obtained following conventional chemical fixation, and immunocytochemistry with an anti-amelogenin antibody indicated no profound differences in the distribution of enamel proteins. CONCLUSIONS: These results indicate that, despite some limitations, it is possible to adequately cryofix tooth organs while preserving the architecture of ameloblasts and permitting immunolocalization of enamel proteins. Furthermore, they confirm the general morphology of secretory stage ameloblasts as currently derived from conventional chemical tissue processing.

Ameloblasts↗
PubMed1994

Expression of c-erbB-2 proto-oncogene-encoded protein (p185erbB-2) in functional rat ameloblasts.

The c-erbB-2 proto-oncogene encodes a transmembrane glycoprotein with tyrosine kinase activity, p185erbB-2, that has been previously localized in some developing and mature epithelia. The possible occurrence of p185 in the inner enamel epithelium of rat tooth germ was here investigated immunocytochemically. Postmitotic functional ameloblasts displayed intense p185-immunoreactivity, thus suggesting that c-erbB-2 proto-oncogene is active during odontogenesis. The expression of this gene in differentiated and functional cells of the enamel organ suggests that its role is not restricted to mitotic events but may also be important in signalling pathways related to other cell activities.

Ameloblasts↗
PubMed1983

Glycosaminoglycans in embryonic mouse teeth and the dissociated dental constituents.

The nature, amounts and distribution of glycosaminoglycans (GAG) before and during odontoblast terminal differentiation were studied. GAG have been isolated from intact mouse tooth germs and from dissociated dental epithelia and dental papillae after labeling with [3H]glucosamine or 35SO2-(4) asd precursor. The kinds and relative amounts of 3H-labeled GAG were analyzed by chromatography on a DEAE-cellulose column and cellulose thin-layer sheets. The amounts of individual GAG relative to total GAG were determined from the elution profiles, whereas their nature was identified by the selective removal of chromatographic peaks after enzymatic or chemical degradation. We found hyaluronate and probably a minute quantity of heparan sulfate in the dental epithelium, while hyaluronate, heparan sulfate, and chondroitin sulfate were the main types of GAG in the dental papilla. The chondroitin sulfate recovered was further fractionated by cellulose thin-layer chromatography into two isomers, namely chondroitin-2-sulfate (the major component) and chondroitin-6-sulfate. Changes in the elution profile from DEAE-cellulose chromatography of tooth GAG extracted from different developmental stages suggest that modifications of GAG occur during odontogenesis. Alcian blue staining localized large amounts of hyaluronate and sulfated GAG along the epithelio-mesenchymal junction. Tissue specificity and changing patterns of GAG were demonstrated during odontogenesis.

Animals↗
PubMed1977

The early mineralization of enamel. Fine structural observations on the cellular localization of calcium with the potassium pyroantimonate technique.

The potassium pyronatimonate technique was used to study the cellular distribution of calcium during the early mineralization of enamel in rat molar tooth germs at the electron microscope level. Differing patterns of calcium distribution were observed in the ameloblast seemingly associated with the appearance of Tomes' process. In the early secretory ameloblast calcium pyroantimonate deposits were observed within the Golgi apparatus, within coated vesicles, within mitochondria and associated with the inner aspect of the cell membrane. However, with the development of Tomes' process the ameloblast no longer demonstrated these discrete deposits of calcium pyroantimonate. Instead they showed a diffuse cytoplasmic staining pattern with no preference for any particular organelle.

Ameloblasts↗
PubMed2001

The dentofacial manifestations of XXXXY syndrome: a case report.

This paper presents a six-year-old patient with XXXXY syndrome, whose oral findings included a cleft soft palate, hyper- or meso-taurodontism in eight primary molars and in the mandibular permanent first molars, five congenitally missing premolars, and delayed development of the permanent tooth germs. The maxillary and mandibular primary central incisors were in a cross-bite relationship. Cephalometric findings showed a short ramus of the mandible and a short maxilla in the anterioposterior plane. The anteroposterior jaw relationship was in harmony. The cross-bite was considered to be due to the retroinclination of the maxillary primary incisors. This case emphasises the importance of regular dental care, and monitoring of facial growth and dental development in children with XXXXY syndrome.

Anodontia↗
PubMed1996

Chemical and X-ray analysis of fluoride, phosphorus, and calcium in human foetal blood and hard tissues.

To evaluate the beneficial effect of prenatal fluoride supplementation, the presence of fluoride in hard tissues in two populations of human foetuses coming from fluoridated (> or = 0.7 parts/10(6) F in drinking water) and non-fluoridated areas (< or = 0.1 parts/10(6) F in drinking water) were compared by chemical analysis and X-ray microanalysis. The fluoride concentrations measured in maternal and venous cord blood confirmed that placental transfer of fluoride was passive when fluoride intake was low. Total fluoride contents of tooth germs and mandibular bone appeared to increase with fluoride level in drinking water. However, these concentrations were too low to be detected by X-ray microanalysis. Phosphorus and calcium total contents were identical in mandibular and femoral bone of both populations. In incisor germs, phosphorus and calcium concentrations in enamel and dentine close to the amelodentinal junction did not differ significantly between the two populations. It is suggested that the low fluoride concentrations in enamel and dentine formed in utero would not have a significant effect on acid solubility.

Abortion, Induced↗
PubMed1985

The pyroantimonate reaction and transcellular transport of calcium in rat molar enamel organs.

The distribution of calcium in the cells of the enamel organ of developing rat molar tooth germs was studied by the pyroantimonate method. It was found that there was a specific localization to the inner leaflet of the plasma membrane of both secretory and maturation phase ameloblasts. This information can be used to support the model for transcellular transport of calcium involving membrane fluidity, with phosphatidylserine as a carrier (Reith 1983). It can also support an alternative model involving movement of calcium ions over a surface of acidic phospholipids on the inner leaflet of the plasma membrane, without involving the necessity for membrane fluidity.

Animals↗
PubMed1988

Cyclic changes in the properties of maturing enamel in the bovine permanent incisor as revealed by glyoxal bis(2-hydroxyanil) staining.

Staining patterns of the surface and interior of maturing enamel of these tooth germs were examined using the glyoxal bis(2-hydroxyanil) (GBHA) solution which chelates with calcium loosely bound to hydroxyapatite to form insoluble red precipitates. An intense red, band-like pattern of GBHA staining, 1-2 mm wide, first appeared on the incisal portion of lingual enamel surface as complete loops, concentrically arranged; these gradually increased in number. Most of the later-formed bands encircled the entire periphery of the maturing enamel surface. GBHA also revealed reactive areas on the labio-lingual, cut and ground surface of maturing enamel, corresponding exactly to the surface GBHA bands. GBHA did not stain EDTA-etched surface enamel, but did reveal regular staining patterns on the ground surface, disclosed after EDTA treatment. These observations suggest an intimate correlation between the properties of interior and surface enamel, at least with regard to the state of local calcium. The maturation of bovine incisor enamel may start at the lingual aspect of the tooth crown.

Aminophenols↗