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At least 883 records · Page 49Linked to original sources
PubMed1982

Localization of fibronectin during dentinogenesis in rat incisor.

Fibronectin (FN) was localized in the dental pulp and predentine at different stages of dentinogenesis by indirect immunofluorescence. Fibronectin was present in the basement membrane between the inner enamel epithelium and the underlying dental mesenchyme and also in mantle predentine. Fibronectin was absent from predentine during further (circumpulpal) dentine formation, indicating that the FN molecule is not directly involved in mineralization. The findings emphasize the difference between the mantle and circumpulpal dentine formation. Fibronectin was localized in the odontoblast layer at the level where the cell processes leave the cell bodies and where the odontoblasts adhere to each other by junctional complexes.

Animals↗
PubMed1982

Proteolytic activity of developing dentine of rat tooth germs revealed by the gelatin-film substrate technique.

The ability of tooth germs to breakdown gelatin was investigated by incubating unfixed cryostat sections of 3-8 day rat molar tooth germs on processed photographic plates. Breakdown of gelatin occurred exclusively in regions which were overlain by developing dentine and bone, suggesting that these tissues contain proteolytic enzymes. As the proteolytic activity occurred at a pH closer to that of the extracellular fluid, i.e. closer to neutrality, it is proposed that neutral proteases, presumably released by odontoblasts, breakdown components of the organic matrix during dentinogenesis. The products of breakdown may, in turn, be taken up by odontoblasts to be further degraded in their extensive lysosomal-vacuolar system. Breakdown and resorption of matrix components may reflect the normal turnover of matrix materials, or may be a mechanism concerned with the regulation of either the amount of materials present in the matrix or its chemical composition during dentinogenesis.

Animals↗
PubMed1984

Immunofluorescent localization and extractability of fibronectin in human dental pulp.

Fibronectin, visualized in premolar pulps by indirect immunofluorescence, was abundant in the odontoblast layer, around blood vessels and in the core of the pulp. Similarity of alignment of fibronectin with the argyrophilic fibres and von Korff fibres was evident. Fibronectin was extracted from pulps after first removing blood by washing with water, confirmed by eventual negative reaction on alpha 2-macroglobulin. Extraction of fibronectin from this remaining tissue was most effectively achieved by treatment with collagenase or hyaluronidase, though in all cases some fibronectin remained, indicating that fibronectin in pulp is not exclusively associated with collagen and/or proteoglycans. The fibronectin quantified by electro-immunoassay and expressed as percentage of dry weight was 0.030 per cent in the water extract, 0.094 per cent in the collagenase extract and 0.109 per cent in the hyaluronidase extract. Twice as much fibronectin was extracted from the apical pulp as from the coronal and middle parts, in accord with earlier findings of a higher collagen content in the radicular part. It is suggested that with the loss of collagen type III during odontoblast differentiation and its reappearance with advancing vascularization of the dental papilla, the amount of fibronectin is similarly altered.

Adolescent↗
PubMed1988

Effects of glycosaminoglycans on in vitro mouse dental cells.

Trypsin-dissociated dental papillae and enamel organs removed from the first lower molars of day-18 and day-19 mouse embryos were cultivated for 2 to 4 days on Millipore filters in DMEM supplemented with 15 per cent fetal calf serum and chondroitin sulphate and hyaluronic acid, individually or together. Three concentrations of glycosaminoglycans (GAGs) were also added to the media (01, 0.2, 0.4 mg/ml). Control cultures were made in the absence of GAGs, and additional experiments performed in which the presence of GAGs was associated with serum-free medium. Elongated and polarized odontoblasts showing synthetic activity were only observed in the presence of serum containing medium supplemented with 0.1 or 0.2 mg/ml of the GAGs. [3H]-thymidine autoradiography demonstrated that these cells were already post-mitotic at the onset of the culture. Polarized ameloblasts were never observed. These data provide evidence that GAGs are able to maintain the polarized state of cultured odontoblasts.

Ameloblasts↗
PubMed1988

A quantitative comparison of osteoclasts in the teeth of the anuran amphibian Xenopus laevis.

An image-analysing computer was used to measure transectional areas of osteoclast cytoplasm and nuclei, the number of nuclei per osteoclast transection, odontoblast height and dentine thickness on serial sections of resorbing, erupting and ankylosed teeth from 3 groups of female frogs of different snout-vent lengths. All parameters except nuclear size were increased significantly between the small and large frogs, suggesting that larger teeth are resorbed by larger osteoclasts. Because more time is required for resorption of the thicker dentine of large frogs, the increased size and nuclear number of the osteoclasts in large specimens may be related to the increased time available for fusion of mononuclear precursor cells. However, in large frogs the proportional increase in cytoplasmic area of osteoclasts was greater than the increase in number of nuclei. This may be related to osteoclast activity, as the height of the odontoblasts also increased with dentine thickness.

Aging↗
PubMed1993

A bromodeoxyuridine immunocytochemical and morphometric study of the influence of growth hormone on cell proliferation in odontogenic mesenchyme of the Lewis dwarf rat.

Cell proliferation was studied in pre-odontoblasts, and in cells of the dental papilla and lingual dental follicle using bromodeoxyuridine immunocytochemistry and morphometry in Bouin's perfused and paraffin-embedded, undemineralized maxillary incisors. Cells in DNA synthesis, as shown by this technique, or in mitosis, were counted. Significantly fewer labelled nuclei, unlabelled nuclei and total nuclei were found in the tissues of growth hormone-deficient dwarf rats than in normal tissues. However, in dwarf rats treated for 6 days with bovine growth hormone, their numbers were equivalent to, or in some instances greater than those in normal tissues. The bromodeoxyuridine labelling index, the ratio of positive to negative nuclei and the mitotic index of pre-odontoblasts in dwarf rats were consistently lower than in normal rats, and were reversible by growth hormone. Growth hormone thus plays a part in odontogenic mesenchymal proliferation.

Ameloblasts↗
PubMed1993

Bone sialoprotein in developing porcine dental tissues: cellular expression and comparison of tissue localization with osteopontin and osteonectin.

Bone sialoprotein (BSP) is a highly sulphated and glycosylated phosphoprotein that is a major constituent of bone and other mineralized connective tissues. Although BSP can mediate cell attachment through an RGD sequence and binds selectively to hydroxyapatite, its precise function in mineralized tissues is unknown. To provide insights into its possible function, affinity-purified polyclonal antibodies directed against porcine BSP were used to demonstrate the histological distribution of this protein in developing porcine mandibular alveolar bone and the associated tooth tissues from 35- and 50-day fetuses. In addition, a porcine cRNA probe was used to determine the cellular expression of BSP in the same tissues by in situ hybridization. Immunoreactivity to BSP protein was restricted to the cells and matrix of the mineralized tissues of alveolar bone and dentine. In dentine, BSP was localized to the odontoblasts and their processes and to the peritubular dentine. In the alveolar bone, immunoreactivity for BSP was evident in osteoblastic cells and osteocytes and in the bone matrix; the older bone stained more strongly than newly formed bone. In addition, BSP appeared to be concentrated in the reversal lines of the rapidly remodelling bone. The distribution of BSP in these tissues revealed distinct differences when compared to osteopontin and SPARC/osteonectin, which are also prominent non-collagenous proteins of mineralized tissues. Most notable was the localization of osteopontin and especially osteonectin in non-mineralizing tissues. The immunoreactivity of osteoblasts and osteocytes for BSP in bone was consistent with the high levels of BSP mRNA revealed by in situ hybridization. However, much lower levels of hybridization were evident in the odontoblasts of developing mandibular molars. These studies demonstrate that BSP is expressed during the early formation of dentine and alveolar bone and that the protein accumulates in the peritubular dentine and bone matrix.

Alveolar Process↗
PubMed1993

The distribution of cellular retinoic acid-binding protein I during odontogenesis in the rat incisor.

Retinoids are important molecules in various aspects of embryological development. Here the distribution of cellular retinoic acid-binding protein I (CRABPI) was studied in the continuously growing incisor of adult rats using an affinity-purified rabbit polyclonal antibody. CRABPI was present throughout the presecretory and secretory ameloblast layer. The protein disappeared from that layer during its maturation phase. The adjacent dental mesenchyme of the developing pulp stained positively for CRABPI, especially in the layer immediately beneath the fully differentiated odontoblasts. Little CRABPI was present in the odontoblast layer itself. The distribution of CRABPI, both in the undifferentiated basal region of the incisor tooth and associated with the cells during hard-tissue formation, suggests a role for this molecule during differentiation and hard-tissue genesis.

Ameloblasts↗
PubMed1993

Immunohistochemical detection of prostaglandin I2 synthase in various calcified tissue-forming cells in rat.

Localization of prostaglandin (PG) I2 synthase immunoreactivity was examined in demineralized sections of rat pulpal, periodontal and skeletal tissues using isn-1, a monoclonal antibody raised against the enzyme. Various calcified tissue-forming cells, i.e. odontoblasts, osteoblasts, osteocytes, cementoblasts, cementocytes and chondrocytes, were similarly immunoreactive for PGI2 synthase, suggesting that they are capable of producing PGI2. In odontoblasts and chondrocytes, the reactivity increased gradually with maturation. Weak immunoreactivity was also observed in endothelial cells and fibroblast-like cells in pulpal and periodontal tissues. However, no reactivity was seen in ameloblasts. These results suggest the possible involvement of PGI2 in the regulation of the metabolism of various calcified tissues. Monoclonal antibodies such as isn-1 may become useful markers of the maturation of calcified tissue-forming cells of mesenchymal origin.

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↗
PubMed1994

Morphological features of dentine and pulp related to dentine sensitivity.

This review considers those structural features of the pulp and dentine relevant to an understanding of dentine sensitivity. It does not discuss innervation, or microvasculature, which are covered in other contributions. The sensitivity of dentine is directly related to the size and patency of the dentinal tubules. Tubular occlusion by peritubular dentine deposition or the formation of other intratubular material would reduce the flow of fluid and diffusion of molecules through dentine. Irregular (reparative) secondary dentine would, because its tubules are not continuous with those of primary dentine, be expected to reduce permeability and fluid flow and decrease sensitivity. Regular secondary dentine would have little or no effect other than by increasing diffusion distances. The odontoblast layer is of limited permeability and could restrict the access of materials diffusing through the dentinal tubules to pulpal axons. Odontoblasts are not involved in the sensory process as special sensory receptors but may, by modifying the local ionic environment, alter the threshold of intradentinal nerves.

Animals↗
PubMed1995

Fine structure of tooth germs during the formation of enameloid matrix in Tilapia nilotica, a teleost fish.

Tooth germs were examined by light and transmission electron microscopy. Collagen fibrils were relatively dispersed and thin at the early and middle stages of formation of the enameloid matrix, when the enameloid layer was thin. At the late stage, the fibrils became thicker, reaching nearly 30 nm dia, and formed the interwoven thick bundles that are characteristic of teleost cap enameloid. Abundant flocculent and/or fine, network-like material, probably representing glycosaminoglycans or proteoglycans, was located between the collagen fibrils. Tall, columnar, inner dental epithelial cells contained abundant rough endoplasmic reticulum and many mitochondria, and a well-developed Golgi apparatus was seen around the nuclei at the late stage. Elongated vesicles enclosing fine, filamentous material that resembled procollagen granules, and large granules containing fibril-like structures that were 150 nm in thickness and had periodic cross-banding at 32-nm intervals, were usually observed near the Golgi apparatus. The contents of the large granules were well stained with phosphotungstic acid, which suggests that inner dental epithelial cells synthesize collagen fibrils. At this time, odontoblasts also contained abundant rough endoplasmic reticulum and mitochondria, a well-developed Golgi, several kinds of granule including those that probably contained procollagen, and many microtubules. It is proposed that odontoblasts are involved in the formation of a considerable portion of the enameloid matrix, including collagen fibrils.

Amelogenesis↗
PubMed1986

Scanning electron microscope study of the predentin-pulpal border zone in human dentin.

Fragments of sound human molars were prepared for the scanning electron microscope (SEM) using modified fixative procedures and the carbon dioxide critical-point method to study the predentin-pulpal border zone. This technique minimizes the usual artifacts related to SEM procedures. The elongated odontoblast bodies are closely related to each other at the predentin level. For the first time in SEM procedures, the cell processes almost completely fill the predentinal tubules. Fibers measuring 0.3 to 0.5 micron in diameter are visible between the odontoblasts and fan out into the predentin. They correspond to the so-called Korff's fibers. Others, measuring less than 0.2 micron in diameter, are visible on the predentinal surface and follow the cell processes into the predentinal tubules. They correspond to nerve fibers. This study demonstrates that the proper use of improved SEM fixative techniques and the carbon dioxide critical-point method provides data on the relation between the different components of the predentin-pulpal border zone, which are in agreement with transmission electron microscope data.

Dental Pulp↗
PubMed1993

Electron microscopic changes in human pulps after intraligamental injection.

Because of its advantages, intraligamental injection is becoming a popular anesthetic technique to achieve anesthesia in vital pulps. This study investigated the possible effects of intraligamental injection on human pulps under electron microscope. Forty-two mandibular and maxillary premolars were scheduled to be extracted for orthodontic reasons after being anesthetized with intraligamental injections of 2% lidocaine, 1:100,000 epinephrine (experimental group). The same anesthetic solution was used on the contralateral teeth with either nerve or field blocks (control group). To examine the effects of ischemia on odontoblasts, 12 anesthetized premolars were extracted, and their pulps were placed in physiologic saline solution for different time intervals (15 minutes to 6 hours). The teeth in the experimental and control groups were then reanesthetized with nerve or field blocks of 3% carbocaine without epinephrine after time periods that ranged from 15 minutes to 28 days. After extraction, the teeth were sectioned vertically and their pulps were fixed in 3% glutaraldehyde. The odontoblastic layer of each pulp was examined under electronic microscope. Nuclear and cytoplasmic changes started an hour after ischemia in the pulps placed in physiologic saline. In contrast, little or no cellular changes occurred in pulps of the experimental or controls groups. On the basis of the results, it appears that intraligamental injection has no long-term deleterious effects on pulps of young human premolars.

Anesthesia, Dental↗
PubMed1989

Retrovirus-induced insertional mutation in Mov13 mice affects collagen I expression in a tissue-specific manner.

In the Mov13 mouse mutant, transcription of the alpha 1 (1) collagen gene is blocked by a retroviral insert in the first intron. We now report that teeth derived from homozygous embryos produce a dentin layer containing normal amounts of collagen 1. In situ hybridization and RNAase protection experiments indicate that the mutant allele is efficiently transcribed in odontoblasts, in contrast to other cell types. Correct splicing of the primary transcript containing the viral sequence results in a functional alpha 1 (1) collagen mRNA. The absence of a mutagenic effect in odontoblasts, as opposed to fibroblasts, suggests that the retroviral insert interferes with tissue-specific transcriptional control of the alpha 1 (1) collagen gene, most likely by inactivating cell-type-specific cis-acting regulatory elements.

Animals↗
PubMed1995

Pulpo-dentinal complex revisited.

OBJECTIVES AND METHODS: The value of the concept of a pulpo-dentinal complex was assessed on human teeth treated according to the ISO test on biological evaluation. The teeth were extracted after 1 or 3 months and examined histologically. Biochemical and biological data available from the dental literature were also re-examined. RESULTS: During the early development of the tooth, pulp and dentine establish close links and form an undivided organ. However, examination of the tissues at later stages of development casts doubt on the validity of such a concept. Major differences are reviewed in this report between the cells (odontoblasts and heterogeneous pulpal cells) and extracellular matrix (collagens, non-collagenic proteins and phospholipids) located either in the odontoblast-dentine area or in the pulp. It seems also that clear-cut differences are detected during inflammatory and repair processes. CONCLUSION: It is concluded that, although the existence of a dentino-pulpal reaction cannot be denied, the concept of a pulpo-dentinal complex is an oversimplification and should be revisited. This may have implications in the evaluation of restorative treatments and in the design of a tissue repair strategy.

Adolescent↗
PubMed2004

The expression pattern of hyaluronan synthase during human tooth development.

In previous studies, hyaluronan (HA) and its major cell surface receptor CD44 have been suggested to play an important role during tooth development. HA synthases (HASs) are the enzymes that polymerize hyaluronan. Data on the expression pattern of HASs during tooth development is lacking and the aim of the present study was to investigate the localisation of HAS by immunohistochemistry in human tooth germs from different developmental stages. The distribution pattern of HAS in the various tissues of the "bell stage" tooth primordia corresponded to that of hyaluronan in most locations: positive HAS immunoreactivity was observed in the dental lamina cells, inner- and outer-enamel epithelium. On the stellate reticulum cells, moderate HAS signal was observed, similar to the layers of the oral epithelium, where faint HAS immunoreactivity was detected. At the early phase of dental hard tissues mineralization, strong HAS immunoreactivity was detected in the odontoblasts and their processes, as well as in the secretory ameloblasts and their apical processes and also, the pulpal mesenchymal cells. The HAS signals observed in odontoblasts and ameloblasts gradually decreased with age. Our results demonstrate that hyaluronan synthesised locally by different dental cells and these results provide additional indirect support to the suggestion that HA may contribute both to the regulation of tooth morphogenesis and dental hard tissue formation.

Ameloblasts↗
PubMed2005

Dentinal defects in Hyp mice not caused by hypophosphatemia alone.

The Hyp mouse is a murine homolog of human X-linked hypophosphatemic rickets and displays hypo-mineralization in bone and dentin due to a defect of the phosphate-regulating gene with homology to endopeptidase on the X chromosome (Phex) gene. It has long been considered that the bone and dentin defects in Hyp mice are caused by hypophosphatemia alone, however, several recent studies have indicated the possibility that intrinsic defects are present in Hyp mice osteoblasts. Further, we previously found a hyper-expression of osteocalcin (OC) mRNA in Hyp mouse odontoblasts and suggested the possibility of the presence of intrinsic defects. In the present study, we evaluated morphological features and OC mRNA expression levels in tooth germs of Nor mice with a normal phex gene and a low concentration of serum phosphate, and compared them to those in Hyp and wild-type mice. Nor mice exhibited low serum phosphate levels, however, did not show the characteristic features of dentin defects seen in Hyp mice, such as widened predentin and hyper-expression of OC mRNA. These results suggest that the hypo-mineralization of dentin in Hyp mice is not dependent on serum phosphate level, but rather is affected by intrinsic defects in odontoblasts.

Animals↗