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At least 1,171 records · Page 65Linked to original sources
PubMed1991

Dental pulp lipids from Bos taurus during odontogenesis.

During the fetal development of the dental pulp, the various lipid classes show no substantial differences in their relative ratios but differences occur between deciduous and permanent teeth. By chromatography, the amount of free cholesterol was found decreased in deciduous and permanent teeth as compared to fetal teeth. Esterified cholesterol increased in permanent teeth and triglyceride levels were high only in developing permanent teeth. Phosphatidylcholine, sphingomyelin and phosphatidylserine were present in higher concentration in permanent unerupted teeth, while phosphatidylethanolamine was at first constant but then decreased during development in the permanent unerupted teeth. These data suggest that lipid changes are related to the assembly of plasma membranes and to the establishment of the innervation during ontogeny and postnatal development of dental pulp.

Aging↗
PubMed1992

Immunocytochemical localization of growth hormone receptor in rat maxillary teeth.

To address the question of what role growth hormone may have in stimulating tooth formation, the distribution of its receptor/binding protein in developing rat incisors and molars was studied immunocytochemically using well-characterized monoclonal antibodies. Ten female 45-day-old Wistar rats were perfused with 4% paraformaldehyde. Five-microns paraffin sections of the growing end of maxillary incisors and molars were cut, deparaffinized and incubated with mouse anti-growth hormone receptor antibodies or control antibodies. A three-layer streptavidin peroxidase technique was used to detect bound antibody. Immunoreaction product was associated primarily with the cytoplasm of cells at certain stages of differentiation. Dividing cells, differentiating preameloblasts and preodontoblasts, secretory ameloblasts and odontoblasts showed immunoreactivity. Undifferentiated dental epithelium cells, stellate reticulum, external dental epithelial cells, mature odontoblasts, and most of cells in the dental papilla were non-reactive. However, at certain stages of tooth development, the stratum intermedium and the external dental epithelium also stained positively. The presence of growth hormone receptor/binding protein in tooth cells at different stages of their development indicates that growth hormone may influence cell proliferation, differentiation and differentiated functions of ameloblasts, odontoblasts and cementoblasts independent of a systemic mediator, and thus may be involved in stimulating odontogenesis directly.

Ameloblasts↗
PubMed1993

In situ localization of tenascin mRNA in developing mouse teeth.

Tenascin is a large extracellular-matrix glycoprotein found in developing connective tissue. A cDNA probe to mouse tenascin, mTN2, was used to determine the cellular origins of this molecule in the murine tooth germ by in situ hybridization. At embryonic day 19, a hybridization signal significantly greater than background was detected with mTN2 in the subodontoblastic layer of the dental mesenchyme and in the inner enamel epithelium of the enamel organ. At postnatal day 1, a signal was detected over pre-odontoblasts and the strata intermedium and externum. No tenascin mRNA was detected in odontoblasts or the stellate reticulum at either age, and hybridization in ameloblasts was not significantly greater than background at postnatal day 1. Thus, much of the tenascin found throughout developing teeth appears to be synthesized by pre-odontoblasts and the inner enamel epithelium, the two populations of cells destined to generate mineralized matrix.

3T3 Cells↗
PubMed1994

Temporal distribution of endogenous retinoids in the embryonic mouse mandible.

Retinoids play an important part in embryonic pattern formation. They are necessary for normal differentiation of odontogenic tissues and, in excess, disrupt the pattern of tooth formation. Excess retinoids produce supernumerary buds of the dental lamina in the diastema region of the mouse embryonic mandible where teeth do not normally form. This effect is coincident with an increase in epithelial proliferation and an alteration in epidermal growth factor mRNA expression (a gene product necessary for tooth formation). It was found by high-performance liquid chromatography that endogenous retinoids are present in the developing murine mandible and that concentrations of some retinoids reach a peak at the time of the initiation of odontogenesis (dental lamina formation).

Animals↗
PubMed1994

Effects of the intermediate retinoid metabolite retinal on the pattern of the dental lamina in vitro.

Retinoids have important roles in pattern formation during embryonic development and might act as endogenous morphogens. They are necessary for normal odontogenesis and excess retinol alters the pattern of odontogenesis producing supernumerary buds of the dental lamina in the diastema region of the mouse mandible. Because the metabolism of retinoids in the developing mandible is unknown, the effects of retinal (an intermediate metabolite in the local conversion of retinol to retinoic acid) on the patterning of odontogenesis were examined. Retinal produces supernumerary buds and enhanced epithelial proliferation in day-9 mandibles in vitro. The endogenous levels of retinal in the mandible at the time of initiation of odontogenesis were also measured by high-performance liquid chromatography. Retinal was detected only at day 10 and not at later stages of development. Local metabolism of this intermediate retinoid may be a rate-determining step in the production of active retinoid metabolites that may control the pattern of the dentition, which is established at the time of the appearance of the dental lamina at embryonic day 12.

Animals↗
PubMed1994

Nerve fibres and cells immunoreactive to neurochemical markers in developing rat molars and supporting tissues.

The distribution of nerve fibres immunoreactive to calcitonin gene-related peptide (CGRP), substance P (SP) and neuropeptide Y (NPY) was compared to the general neurochemical markers for nerves and neuroendocrine cells protein gene product 9.5 (PGP 9.5) and neurone-specific enolase (NSE), by use of the avidin-biotin peroxidase complex method in developing dental structures in rats aged 13 to 27 days. A substantially greater part of the nerve fibres was immunoreactive to CGRP and SP than to NPY. In the bell stage, nerve fibres immunoreactive to PGP 9.5, CGRP and SP were found in the dental follicle but not in the dental papilla and stellate reticulum. In the advanced bell stage, after initiation of dentine and enamel formation, PGP 9.5, CGRP- and SP-immunoreactive fibres were found in the dental papilla, while the first NPY-immunoreactive fibres were observed in the papilla when root formation started. Concomitant with the beginning of root development, a subodontoblastic nerve plexus was gradually formed and PGP 9.5-, CGRP- and SP-immunoreactive fibres were found within the dentinal tubules. From the start of root formation, CGRP-, SP- and NPY-immunoreactive nerves were shown in the developing periodontal ligament, although a mature distribution pattern was not observed until root formation was nearly completed. Ameloblasts, odontoblasts and cell-like structures in the outer enamel epithelium and within the dental lamina were PGP 9.5-immunoreactive at the bell stage. As the tooth matured, the immunolabelling gradually decreased, but was still present in some odontoblasts after tooth eruption. NSE-immunoreactive, cell-like structures were found in the periphery of the dental follicle, and persisted close to alveolar bone in the periodontal ligament when the tooth reached occlusion. Hence, it may be concluded that sensory nerves containing SP and CGRP are present in the pulp in advance of sympathetic nerves immunoreactive to NPY.

Alveolar Process↗
PubMed1995

Instruction by retinoic acid of incisor morphology in the mouse embryonic mandible.

Endogenous retinoids are present in the embryonic mouse mandible and reach a peak in concentration at the time of the formation of the dental lamina. All-trans retinoic acid is present in a 10-fold higher concentration in the future incisor region of the mouse embryonic mandible at day 11.5. It was found here that exogenous all-trans retinoic acid has pleiotropic effects on the pattern of odontogenesis when applied before the formation of the dental lamina. These effects include a change in the pattern of the dental lamina, supernumerary buds and incisors in the diastema region, and replacement of molars with incisors in the molar region. Thus retinoic acid appears to instruct incisor morphology in the mouse embryonic mandible.

Animals↗
PubMed1975

Odontodysplasia. Report of two cases and review of the literature.

Odontodysplasia is a rare developmental anomaly affecting the tooth structures in both deciduous and permanent dentitions. The enamel is thin and uneven in thickness, and the detinal tissue surrounds very large pulp chambers. Denticles are present in the pulp organ. The maxilla is involved twice as frequently as the mandible. Most of the affected teeth are in the anterior segments; however, all other teeth can be affected. The cause is unknown. Because of the tendency of the affected teeth to develop abscesses, the most common treatment is extraction. Two additional cases are reported, and the literature is reviewed.

Abscess↗
PubMed1975

Odontogenic myxoma. A clinical and ultrastructural study.

The odontogenic myxoma is an uncommon neoplasm of the jaws that is believed to arise from the primitive, mesenchymal portion of the tooth germ. This study surveys nine cases of odontogenic myxoma of the jaws. Analysis of the clinical material revealed that the myxoma occurred most frequently in the posterior regions of the mandible and will recur if initial therapy is too conservative. The average age of the patients in this series was 26.5 years. Five cases involved females and four involved males. Electron microscope findings revealed that the tumor cells are probably responsible for the secretion of the myxomatous intercellular material of the neoplasm.

Adolescent↗
PubMed1988

Multiple dental follicles with odontogenic fibroma-like changes (WHO type).

A 15-year-old boy, in the case presented in this article, had 13 unerupted teeth, each associated with hyperplastic pericoronal tissue that showed histologic features suggestive of the WHO type of odontogenic fibroma. The etiology, clinical features, radiographic findings, and histopathology of the odontogenic fibroma are reviewed. It is suggested that the unusual pericoronal findings represent a hamartomatous change.

Adolescent↗
PubMed1991

Root agenesis in developing canines as a complication of intranasal antrostomy.

A case is reported in which the roots of both maxillary canines failed to develop, a defect that could be traced to antral surgery when the patient was 8 years of age. The differential diagnosis of such a finding is proffered. The maxillary antrum is described, and aspects of the surgical procedure, the nasal antrostomy, used in this patient are discussed. A brief outline of current thought on the mechanisms of eruption of teeth is appropriate, and treatment of the symptomatic tooth is mentioned.

Adult↗
PubMed1994

Ultrastructure of quick-frozen secretory ameloblasts of the rat molar tooth.

Ameloblasts in molar tooth germs from 4 to 12-day-old neonatal rats were quick-frozen and then freeze-substituted in acetone-tannic acid and acetone-osmium tetroxide. Following quick freezing and freeze-substitution, the preservation of ameloblasts was principally the same as seen in conventionally-fixed ones. Several differences, however, became apparent between two methods. Concerning enamel formation, the quick-freezing procedure greatly improved the preservation including that of the extrusion of secretory granules into the extracellular space. The exocytosis is a type of merocrine secretion. The precursor stippled material was demonstrated at the front of Tomes' processes and in the intercellular space of the distal terminal junction. In the more advanced stage, the stippled material tended to decrease gradually in amount. Prior to the formation of the typical Tomes' process, large secretory granules fused directly with the distal plasma membrane, which plays a role in the formation of prismless enamel. After the typical Tomes' process had formed, secretory granules containing electron-dense material instead of the large secretory granules accumulated in the distal portion of the Tomes' process. These latter secretory granules had two different destinations; i.e. the granules discharged their contents into the infoldings of the distal part of Tomes' process and into the infoldings of the lateral cell membrane. These types of secretion seem to have a functional role in the rod or inter-rod enamel formation. The ultrastructure of the stippled material consisted of 3-dimensionally interconnected strands after quick freezing, which is different from the appearance of granules embedded in amorphous material after conventional fixation. The stippled material was seen in the intercrystal space among the newly formed crystals. Also, an extensive tubulo-vesicular structure was preserved in both the cell body and Tomes' process. The present data suggest that the membrane of this structure showed a smooth contour opening to the extracellular space, and also an intimate relationship with the secretory granules.

Ameloblasts↗