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At least 19 recordsLinked to original sources
PubMed1979

The role of ascorbic acid on the structural integrity of developing tooth germs.

Tooth germs grown in ascorbate deficient medium for up to 20 days underwent progressive and widespread changes. Proliferation and differentiation of preameloblasts and preodontoblasts progressed normally. Newly differentiated odontoblasts, however, became vacuolated when they began secreting: this suggested a metabolic disturbance. Failure to maintain differentiated odontoblasts, ameloblasts and pulpal cells resulted in aberrant dentin matrix, cessation of dentin production, and finally overall structural collapse with loss of normal morphology. Biochemical studies then were undertaken to define the lesion involved. The relative rate of collagen synthesis in ascorbate deficient cultures was comparable to that of ascorbate supplemented cultures, but the collagen was found to be underhydroxylated. In this state it would be unstable at 37 degrees and subject to preferential degradation. This correlates with the observation that a major fraction of the hydroxyproline in the scorbutic cultures was found in the medium as small molecular weight peptides. The overall effect of ascorbate deficiency was to deprive the tooth germ of the normal quality and quantity of collagen resulting in the characteristic histological and structural abnormalities observed. Flattening and deterioration due to structural failure most likely resulted from abnormal extracellular matrix synthesis in the supportive pulp and dentin due to the aberrant collagen.

Animals↗
PubMed1991

Immunocytochemical and immunochemical detection of a 32 kDa nonamelogenin and related proteins in porcine tooth germs.

Porcine tooth germ was investigated immunochemically and immunocytochemically using antibodies against a synthetic N-terminal peptide fragment from a 32 kDa nonamelogenin found in the inner (old) secretory enamel. In immunochemical preparations, these antibodies reacted to many proteins of differing molecular weights, especially to 140 kDa, 89 kDa, 56 kDa, 45 kDa, and 32 kDa proteins. Analysis of the layers of enamel suggested that the 140 kDa and/or 89 kDa proteins, both of which were found in newly formed enamel, were the parental proteins secreted by the ameloblasts, and that they were degraded to produce 32 kDa and other low molecular-weight proteins associated with progressive mineralization. In immunohistochemical preparation, immunoreactivity at the differentiation stage was detected initially over the amorphous dense material or fine fibrils around calcified globules in predentin, while the stippled material was devoid of immunoreactivity. The amorphous dense material seemed to give rise to a continuous layer of initial enamel. At the matrix formation stage, the immunoreactivity of immature enamel just beneath the putative secretory face of the Tomes' processes was intense. From the surface of the enamel matrix to a depth of about 100 microns, immunoreactivity of prism sheaths was weaker than that of enamel prisms, producing a reverse honeycomb pattern. In the enamel matrix deeper than 100 microns, immunoreactivity was weak and homogeneously distributed. The Golgi apparatus and secretory granules of the secretory ameloblasts showed immunoreactivity. These results suggest that the likely parent proteins of the 32 kDa nonamelogenin protein, i.e., the 140 kDa and/or 89 kDa proteins, play a significant role in the calcification of the enamel matrix.

Ameloblasts↗
PubMed1976

In vitro utilization of exogenous procollagen by embryonic tooth germs.

Embryonic mouse tooth germs treated with L-azetidine-2-carboxylic acid cease their development, undergo a regression of the enamel organ, and do not maintain the histological characteristics of the explanted dental organ. On the other hand if procollagen is added exogenously to explants continously treated with L-azetidine, the effects of the inhibitor are not seen and the tissue is maintained. Thus, exogenously supplied procollagen supports morphogenesis in tooth rudiments that are unable to synthesize procollagen.

Animals↗
PubMed1989

Ultrastructure of a new generation of odontoblasts in grafted coronal tissues of mouse molar tooth germs.

Third molar tooth germs were removed from 14-day-old mice and freed from the enamel organ and follicle. After section of the apical tissues, including Hertwig's sheath, they were transplanted in 1-day-old newborn mice of the same lineage. Electron microscopy of grafts removed 7, 14 and 21 days later showed that, following the disappearance of the initial layer of odontoblasts and a period of adaptation, 14 days after transplantation newly differentiated odontoblasts deposited tubular dentine. The dentine matrix production was increased over that of controls, demonstrating that synthesis was accelerated, possibly because of lack of nerves in the grafts. Numerous characteristic structures that might be involved in the transit of proteoglycans from the Golgi apparatus were seen, as far as the extremity of the odontoblast processes. The particular experimental conditions allowed the observation in the neck region of the odontoblast of a concentration of coated vesicles which might be involved in cellular lengthening. Thus, in the presence of a fine and regular vascular network, a new generation of odontoblasts may differentiate, even in the absence of epithelial and nervous elements, and so predentine may contain inductive factors that allow the odontoblastic differentiation of pulp cells in contact with it.

Animals↗
PubMed1991

[A study of root resorption of deciduous teeth in dogs. Influence of successional tooth germ and occlusal force].

The role of successional tooth germ and occlusal force in root resorption of mandibular second deciduous molars was studied in 24 beagle dogs by means of radiographic and histologic evaluations. 70 days after birth their mandibular right third permanent premolar germs were surgically removed, and in 10 of the dogs the maxillary right and left second deciduous molars were extracted to decrease the occlusal force on the mandibular second deciduous molars. 1) When successional tooth germs were present, whether the occlusal force was normal or decreased, the alveolar bone and deciduous tooth adjacent to the tooth germ were resorbed, accompanied by eruption of the permanent tooth. After the resorption of the deciduous tooth reached half of the root, many odontoclasts were observed in the dental pulp of the deciduous tooth. The root resorption was hastened by internal resorption. 2) When successional tooth germs were removed, whether the occlusal force was normal or decreased, the root resorption was delayed. The resorption from the root surface progressed very slowly, but shortly after this resorption reached the pulp, internal resorption occurred and the deciduous tooth was resorbed in short time. 3) When the occlusal force was decreased, in the deciduous teeth in which successional tooth germs were present, the tooth resorption tended to delay to a later time. However in the deciduous teeth from which the successional tooth germs were removed, the processes of tooth resorption was very different in individuals, the difference between tooth resorption in normal occlusal force and in decreased occlusal force was not clear. 4) In all groups, shallow resorption on the deciduous root surface was observed before the successional tooth started to erupt, and this resorption was apart from the tooth germ. By repeating resorptive periods and resting periods, this resorption progressed according to the increase in age, and in the resting period, resorption was repaired by new deposits of cementum.

Animals↗
PubMed1989

[Effect of iodoform on development of cultured tooth-germs of newborn Syrian hamsters].

To examine the effect of iodoform, widely used as a component of filling sealer for root canals, on differentiation and development of tooth-germs, tooth-germs of second molars from newborn Syrian hamsters were cultivated overnight and treated with various concentrations of iodoform for 48 hours. They were subsequently transplanted into the cheek pouch of Syrian hamsters and were subjected to histo chemical examinations three weeks later. 86% of the seven tooth germs examined survived treatment with 1.0 microgram/ml iodoform, as determined by morphology of tooth-germs. The ratio of survival decreased with increasing doses of iodoform, e.g. 63%, 37%, and 13% for 3.3 micrograms/ml, 6.6 micrograms/ml and 10.0 micrograms/ml iodoform, respectively. In untreated tooth-germs, a similar level of survival was obtained with treatment using 1.0 microgram/ml iodoform. Although treatment with 1.0 microgram/ml iodoform showed a survival similar to untreated tooth-germs, the treatment induced a considerable level of aplasia of enamel and dentin in the dental crowns. Meanwhile, higher dose of iodoform was required for induction of aplasia or depression of the dental pulp or root dentain. These results indicate that iodoform over the dose of 1.0 microgram/ml is toxic to cultured tooth-germs of Syrian hamsters and inhibits differentiation or development of the tooth-germs with tissue specificity.

Animals↗
PubMed1989

Innervation of mouse molars during the early states of tooth germ development.

The topography of nerves and first molar tooth germs in 11-14-day embryos was studied using silver-impregnated serial sections. Nerve fibers growing toward the developing tooth germ became visible on the 12th day, while the first sign of molar tooth differentiation was found as a thickening of the oral epithelium in 11-day embryos. From the 12th to 13th day the nerve fibers spread, forming a plexus close to the base of the tooth bud, and on the 14th day some entered into the dental follicle of the tooth germ at the early cap stage. However, no nerve fiber was found growing into the dental papilla during the observation period. The observations showed that the earliest nerve fibers running toward the tooth forming area appeared after the histogenesis of the tooth germ started, and the timing and pattern of the innervation of the tooth germs revealed that tooth germs are a useful model for investigating the mechanism of nerve growth into developing peripheral organs.

Animals↗
PubMed1976

Effect of ascorbic acid deficiency on mouse second molar tooth germs cultivated in vitro.

Mandibular second molar tooth germs from two-day old mice were cultured in vitro, on millipore membranes, for periods of up to 20 days in liquid medium with or without added ascorbic acid. Tooth germs grown in ascorbate medium were characterized by relatively normal growth, differentiation, morphology and histology. Cuspation patterns were maintained. The epithelial root sheath continued to grow along the millipore membrane. Tooth germs cultured in ascorbate-deficient medium manifested a consistent and striking failure in maintenance of differentiated odontoblastic and ameloblastic tissue with arrest of predentin synthesis, severe structural collapse and reduction in size. Cuspation patterns were lost in scorbutic molars, with sinking of surface layers into pulpal tissue and flattening of the entire organ. This resulted in a lack of recognizable morphology and in severe disorganization of tissues. Only growing areas of the root sheath with associated proliferation of preameloblasts and pre-odontoblasts and adjacent pulpal tissue remained normal and refractory to ascorbate deficiency. Odontoblastic as well as ameloblastic layers were disrupted and cells were dedifferentiated. Newly differentiated odontoblasts became highly vacuolated when they became polarized and started to secrete extracellular matrix.

Ameloblasts↗
PubMed1979

Sensitivy of mouse molar tooth germs to x-ray irradiation in vitro.

Molar tooth germs, extirpated from 18-day mouse fetuses were cultured on Millipore filter strips in Falcon organ culture dishes. The tooth germs were exposed to 250 kVcp X-rays at 106 R/min. for a total exposure of 1 600 R. Tissues were harvested on a daily basis for a total period of 12 days and were examined microscopically, utilizing H and E stain. Severe disorganization of the tooth germs was evident within 24 hours of irradiation. The basement membrane became hyalinized; pyknotic nuclei and lysed cells were observed throughout the dental papilla, but mostly in the regions of the presumptive cusps. Although a thin layer of predentin was elaborated by the odontoblasts, the matrix failed to calcify and enamel matrix was not produced. Cultures older than 10 days demonstrated extensive cell death. The entire pulp was reduced to a mass of necrotic cells and the ameloblastic layer consisted of an epithelial remnant covering the cuspal tips.

Ameloblasts↗
PubMed1978

Action of 5-bromodeoxyuridine on tooth germs "in vitro". II. - Effects on collagen synthesis.

The first lower molar tooth germs removed from 16-day-old mouse embryos were cultured for 2 days on a standard medium and then for 24 hours on the same medium containing BrdU (treated tooth germs) or not (controls). We attempted to study the effects of 5-Bromodeoxyuridine on the type I and type III collagen synthesis 24 (stage 16 + 4) and 72 (stage 16 + 6) hours after the incorporation of this thymidine analogue. At stage 16 + 4, type I and type III collagen were synthesized both in control and BrdU-treated tooth germs. However BrdU induced quantitative modifications in the type I collagen synthesis which might be explained by modifications in the turnover of this type of collagen. At stage 16 + 6, the BrdU treatment resulted in the inhibition of the terminal differentiation of odontoblasts. Consequently, the normal amplification of collagen type I synthesis could not occur. However, both control and BrdU-treated tooth germs synthesized type I and type III collagen. Quantitatively, the synthesis of type III collagen was slightly affected by BrdU treatment.

Animals↗
PubMedDate not supplied

45Ca uptake in tooth germs: effects of parathormone, calcitonin and propranolol.

Tooth germs harvested from 6-day-old rats were incubated in a 45Ca-containing medium for 6 hours. The addition of PTH consistently stimulated the increase in 45Ca uptake, while calcitonin significantly reduced both the PTH-stimulated incorporation and the spontaneous one. Dibutyrul CAMP (3.5 mM) had no effects. Propranolol significantly inhibited the spontaneous and stimulated 45Ca uptake. Results obtained support the concept that the two hormones have a clear influence on calcium entering the tooth germs in full calcification process probably by early membrane effect.

Animals↗
PubMed1977

Mitochondrial granule distribution in tooth germ cells.

Incisor and molar tooth germs of albino rats sacrificed at the eighteenth and twentieth days in utero and one to seven days after birth were studied with light and electron microscopy. Observations of the various stages of tooth development in molars established that intramitochondrial granules in odontoblasts were comparable to the intramitochondrial granules of other hard tissue cells. These electron-dense deposits appeared in mitochondria in an appreciable number only when odontoblasts become engaged in dentin mineralization. When dentin mineralization was advanced the odontoblast mitochondria appeared devoid of these deposits. Mesenchymal cells and preodontoblasts of the pulp were not involved in this activity.

Animals↗
PubMed1991

[In vitro effect of chlorpromazine on the mineralization of tooth germ in mice--comparison with that of retinoic acid and HEBP].

Effects of chlorpromazine on the mineralization and alkaline phosphatase activity (ALP) in the tooth germ were examined and compared with those of retinoic acid and HEBP (1-hydroxyethylidene-1, 1-bisphosphonate). Mandibular first molars from 17-day-old mouse embryos were cultured with or without drugs. Calcium content and ALP in the tooth germ increased gradually from 0 to 7 days in culture, the increase of calcium being preceded by that of ALP. Retinoic acid suppressed increases of calcium and ALP in the tooth germ but not in the specimens precultured for 2 days, suggesting that retinoic acid inhibits the mineralization at an early developmental stage of the tooth. HEBP, a physiochemical inhibitor of mineralization, suppressed the increase of calcium, but significantly enhanced the increased of ALP in the tooth germ. Chlorpromazine, which has an antagonistic action towards calmodulin, also suppressed the increases of calcium and ALP in the tooth germ. Calmodulin antagonists W-7 and W-5 similarly suppressed the increases of calcium and ALP; W-5 had less effects on both calcium and ALP. These results indicate that calmodulin may be involved in the regulation of the mineralization in the tooth germ. These drugs are shown to possess different modes of inhibitory action on the mineralization.

Alkaline Phosphatase↗
PubMed1989

[In vitro cultivation of tooth germs (in mice)].

Mouse molars tooth buds on the bell stage were cultured, to investigate the best medium for their maintainance and their eventual clinical use. Tooth germs were cultivated during 3 to 8 days in three different medium: Eagle basal medium (liquid medium), agar-solidified medium and chick chorioallantoic membrane. The grafts were examined by light microscopy. Mesenchymal and atypical cells were counted in experimental and control groups. Our results showed that liquid medium was the best for 3-days buds cultures. Chorioallantoic membrane and agar-solidified medium showed better results for the maintainance of bud cultures for 8-day test. The objective of this study is to maintain in vitro tooth buds cultures for future transplants. This will also provide for the possibility of a more in-depth study of normal odontogenesis.

Animals↗
PubMed1989

Patterns of expression of intermediate filaments in ameloblastoma and human fetal tooth germ.

Monoclonal antibodies (Mab) were used to study the expression of cytokeratins and vimentin in various histological types of ameloblastoma and in human fetal tooth germ. The ameloblastoma and the tooth germ epithelia showed characteristics of both simple glandular and stratified squamous epithelial cells. Cytokeratin No. 18 was detected focally in most ameloblastomas studied but not in fetal odontogenic epithelia. Cytokeratins Nos. 8 and 19 were expressed in all epithelial elements of ameloblastomas and tooth germs. Only two tumors showed focally characteristics of keratinizing epithelia also seen in dental lamina but not in the enamel organ. All tumors except the granular cell ameloblastoma showed a variable coexpression of vimentin and cytokeratins in their neoplastic epithelia. A similar coexpression was detected in the stellate reticulum cells of the developing tooth. Ameloblastoma and human tooth germ epithelia share complex pattern of cytokeratin polypeptides together with coexpression of vimentin. The results strongly support the theory that ameloblastomas are of odontogenic origin and not direct derivatives of basal cells of oral epithelium or epidermis.

Adolescent↗