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PubMed1997

A light microscopic and ultrastructural examination of calcified dental tissues of horses: 3. Dentine.

Ultrastructural examinations of equine dentine found that dentinal tubules extended from the amelodentinal junction towards the pulp forming primary curvatures. The number of dentinal tubules/unit area and their diameters increased significantly from the amelodentinal junction towards the pulp cavities, particularly in regular secondary dentine, but irregular secondary (tertiary) dentine contained no dentinal tubules. Dentinal tubules contained odontoblast processes that appeared to extend as far as the amelodentinal junction, but due to iatrogenic loss during specimen preparation, odontoblasts were seldom found in regular secondary dentine. In primary dentine, the dentinal tubules were surrounded by large amounts of peritubular dentine that increased in diameter from the amelodentinal junction towards the junction of primary and secondary dentine. The site of the dentinal tubule within the peritubular dentine varied at different dentinal sites. Peritubular dentine was present in primary dentine only and was surrounded by a thin layer of intertubular dentine. When acid etched, peritubular dentine gave dentine a honeycomb appearance adjacent to the junction of primary and secondary dentine.

Animals↗
PubMed1985

Differential rate of dentin formation on human deciduous anterior tooth surfaces deduced from tetracycline labeling.

Distances between the intersecting points of two fluorescent lines with the outer dentin surface were measured on enlarged microphotographs of ground sections of human deciduous anterior teeth. The results suggested that: extension of odontoblast differentiation is greater on the lingual than on the labial side during the 8 months following birth in incisors, and during the first year in canines; it is greater on the distal than on the mesial side during the 3 months following birth in incisors, and during the first year in canines; in the incisors, dentin formation of newly differentiated odontoblasts is more active on the distal than on the mesial side during the 8 months following birth.

Dentin↗
PubMed1988

Autoradiographic investigation of effects of high-dose colchicine on dentinogenesis in rat incisors.

Twelve female Wistar rats received 1.5 mg/kg of colchicine (CLC) intravenously. Control animals were similarly injected with isotonic saline solution. The animals were killed 5 h, 24 h, 3 days and 7 days after injection. Ninety minutes prior to sacrifice, all animals received an intraperitoneal injection of 3H-proline. Autoradiograms of maxillary incisors showed that CLC increased the retention of the labeled precursor in the odontoblasts. It was also shown that the odontoblasts in the different sectors of the rat incisor present different sensitivities to the CLC action.

Animals↗
PubMed1989

Innervation of the incisors and periodontal ligament in several rodents: an immunohistochemical study of neurofilament protein and glia-specific S-100 protein.

The present immunohistochemical study by use of antisera against neurofilament protein (NFP) and S-100 protein dealt with the innervation of the upper incisors and periodontal ligament in five species of rodents including the guinea pig, hamster, Mongolian gerbil (Meriones unguicularis), mouse and squirrel (Tamias sibiricus). The innervation pattern of the periodontal ligament and dental pulp in the incisors of five rodents was fundamentally identical to that in the rat, which we have previously demonstrated by the same method. The NFP-positive Ruffini-like corpuscles were concentrated in the middle region of the lingual periodontal ligament in all the species examined, suggesting that this particular arrangement of Ruffini-like corpuscles, possibly stretch receptors, was essential to the rodent incisor. The labial periodontal ligament, on the other hand, contained less numerous NFP-positive nerves, these terminating among collagen fibers as free endings. The gerbil and squirrel in particular possessed only a few nerve fibers in the labial periodontal ligament. It was thus presumed that the labial periodontal ligament might be less significant as a mechanoreceptive site than the lingual periodontal ligament. The NFP-positive pulpal nerves, beaded or smooth in shape, ran parallel to the tooth axis, but never extended to the odontoblastic layer; no subodontoblastic plexus was found in the incisors of any of the rodents. S-100-immunopositive nervous elements were distributed in the periodontal ligament and dental pulp of all the rodent species examined, showing a distribution pattern similar to the NFP-positive nerves. Only in the squirrel did odontoblasts show an intense S-100 immunoreactivity.

Animals↗
PubMed1977

Lymphatic vessels of the human dental pulp.

Noncarious teeth obtained from individuals 15 to 50 years of age were used to study the lymphatic drainage of the human pulp. Thick sections (50 to 150 microns) were stained with iron hematoxylin for the demonstration of lymph and blood vessels. Lymph capillaries originated as blind sacs in the odontoblastic layer and in the pulp proper near the pulpo-odontoblastic border. They drained into small thin-walled collecting vessels that were irregular in shape and showed great variability in their drainage patterns. Communications between these vessels were very common. The larger conducting lymphatic vessels accompanied the blood vessels and nerves in their course through the pulp. They could be identified by their thin walls and small size. The large caliber lymphatic vessels contained valves, a structure not present in the veins of the same size. The conducting lymphatic vessels passed through the roots as individual units without draining into a large single vessel. The lymphatic vessels of the human pulp must be considered as a pathway for the removal of excessive tissue fluid in normal and diseased pulps.

Adolescent↗
PubMed1987

Calbindin-D28 kappa localization in rat molars during odontogenesis.

Specific antiserum raised against Calbindin-D28 kappa, a vitamin D-dependent calcium-binding protein (CaBP) isolated from chick intestine, was used for localization of the protein in developing rat molars. Previously, CaBP had been localized in specific cells associated with the continuously erupting rat incisor: late pre-secretory ameloblasts, secretory and maturation zone ameloblasts, stratum intermedium cells adjacent to ameloblasts in the late zone of enamel secretion, and papillary cells underlying maturation zone ameloblasts. In this study, the peroxidase anti-peroxidase technique was used for localization of the peroxidase anti-peroxidase technique was used for localization of CaBP in histological sections of rat mandibles from 18-day-old rat embryos through 20-day-old neonates. CaBP was not detected in any cells of the enamel organ, dental papilla, or dental sac during early odontogenesis from the dental lamina stage through the advanced bell stage. The protein first appeared in secretory ameloblasts which were situated opposite odontoblasts with newly secreted dentin. CaBP was present in the cytoplasm of more mature ameloblasts, but not in less mature ameloblasts. Some stratum intermedium cells subjacent to well-developed secretory and maturation zone ameloblasts also contained CaBP. The protein was not detected in odontoblasts, pulp cells, or other cells associated with the developing molars. It was also absent from the demineralized enamel and dentin matrix. In developing rat molars, the time-course of appearance of CaBP, a protein dependent for its synthesis on the vitamin D endocrine system in other organ systems, suggests a potential direct role of this hormonal system in enamel mineralization.

Ameloblasts↗
PubMed1990

Inductive influences of demineralized dentin and bone matrix on pulp cells: an approach of secondary dentinogenesis.

The effects of demineralized dentin and bone matrix on dental ectomesenchymal cells were evaluated after observation periods of two or three weeks. Autogenous dentin and bone matrix, obtained from the crowns of primary molars or maxillary cortical bone, respectively, were demineralized with 3% acetic acid and implanted into pulpal or papilla sites of erupting dog teeth: first molars, fourth premolars, and canines. Dentin histogenesis associated with odontoblastic arrangement was demonstrated in relation to all dentin implants in pulpal sites. Deposition of osteodentin, followed in some areas by tubular predentin formation, was observed in contact with bone implants in pulpal sites. In papilla sites, the dentin implantation exhibited bone-like matrix formation, while bone implants were encapsulated by connective tissue. The interactions of pulp cells with demineralized dentin matrix constitute a model for experimental induction of secondary dentinogenesis and odontoblast-like cell differentiation.

Animals↗
PubMed1993

A chondroitin sulfate epitope in mammalian dental pulp and its developmental expression in mouse dental papilla.

The molecular specificity of the dental papilla of a bell-stage tooth was studied by production of dental-papilla-reactive monoclonal antibodies (Mabs). One of the Mabs, designated 7C5, recognized an epitope present in glycosaminoglycan. Several lines of evidence suggested that the 7C5-epitope consists of chondroitin 6-sulfate. The Mab did not react with mouse dental epithelium, but reacted uniformly with mesenchymal tissue in the mandibular process and accumulated in the dental sac and in the papilla of bell-stage tooth germs. The 7C5-staining was lost from the differentiating odontoblasts, while the staining in the molar tooth papilla was accumulated in the subodontoblastic layer. In the developing mouse incisor, the 7C5-epitope was restricted to the lingual-posterior area. The 7C5-epitope was also present in pulpal tissue and predentin of different types of teeth of various mammalian species, including man, sheep, swine, and rat. Collagenase pre-treatment of tissue sections abolished the bulk of the 7C5-reactivity in peridental mesenchyme during embryonic stages while leaving the staining of the dental papilla intact. In newborn and adult teeth, collagenase also impaired the reactivity in the pulp except for the subodontoblastic layer. This suggests the existence of different subpopulations of the 7C5-epitope containing proteoglycans in dental papilla and pulp. A high-molecular-weight proteoglycan, sensitive to chondroitinase ABC but not to heparinase or heparitinase, was immunoprecipitated by 7C5 from extracts of bell-stage mouse tooth germs. We suggest that the evolutionary conservation of chondroitin 6-sulfate in the dental pulp reflects its properties as non-terminally differentiated tissue and perhaps the retention of a potential to differentiate to odontoblasts.

Animals↗
PubMed1997

Identification, partial characterization, and distribution of versican and link protein in bovine dental pulp.

The dynamics of changes in the cellularity and extracellular matrix composition of dental pulp varies considerably during tooth development and maturation. In this paper, we studied matrix proteoglycans where we hypothesized that they played important roles in structural, spatial, and transport aspects of pulpal development and maintenance. The pulpal tissue was collected from partially erupted bovine incisors, pulverized, and then extracted with 6 M guanidine-HCl. The extract was subjected to anion column chromatography (DEAE-8HR), and the fractions collected were screened by dot-blot immunoassay by means of monoclonal antibodies generated against 4- and 6-sulfated chondroitin sulfate isomers, and keratan sulfate, 2-B-6, 3-B-3, and 5-D-4, respectively. The chondroitin-6-sulfate was the major glycosaminoglycan species and occurred as a large-molecular-weight proteoglycan (> 500 kDa). After further purification, it was subjected to agarose/acrylamide composite gel electrophoresis, and it migrated as a single band stained with Stains-All. The band was immunopositive against antibody 3-B-3 by Western blot analysis. The partial amino acid sequence analyses of the core protein clearly indicated this molecule to be versican. The presence of link protein was also confirmed by Western blot analysis with an anti-link protein monoclonal antibody, 8-A-4. Furthermore, immunohistochemical study indicated that the distributions of versican and link protein coincide in the dental pulp and are enriched in the peripheral area of the tissue just beneath the odontoblast layer. Since the dental pulp contains hyaluronan, versican may bind to hyaluronan via its hyaluronan-binding domain, where this association is stabilized by link protein. This complex, then, could form large hydrated proteoglycan aggregates that fill the extracellular space, support odontoblasts, and/or facilitate the transport function of metabolites and nutrients within the tissue.

Amino Acid Sequence↗
PubMed2004

Immunolocalization of enamelysin (matrix metalloproteinase-20) in the forming rat incisor.

In the rat model, we used the continuously growing incisor to study the expression pattern of matrix metalloproteinase-20 (MMP-20) during the formation of mineralized dental tissues. Casein zymography analysis of extracts of the forming part of the incisor revealed lysis bands corresponding to both the latent form at 57 kD and the active 46- and 41-kD forms, whereas omission of proteinase inhibitors during protein extraction resulted in a single band at 21 kD. A higher molecular weight form of 78 kD was also stained with MMP-20 and TIMP-2 antibodies in Western blotting, and was therefore believed to correspond to an MMP-20/TIMP-2 complex. Immunohistochemical and immunogold electron microscopic results demonstrated strong MMP-20 staining in the forming outer enamel, which diminished near the dentino-enamel junction, but dentin and predentin were unstained. A strong concentration of MMP-20 was seen in the stratum intermedium (SI), particularly at the earlier stages of enamel development. Our results confirm the presence of MMP-20 protein in ameloblasts and odontoblasts of rat incisor and show it to be localized in the same sites of the forming enamel as amelogenin. Their expression is transient in odontoblasts but persists in ameloblasts, and in both cases the expression of amelogenin preceded that of MMP-20 suggesting a developmentally controlled regulation.

Amelogenin↗
PubMedDate not supplied

Dental pulp infarction in female rats following inhalation exposure to 2-butoxyethanol.

Female Fischer 344 (F344)/N rats (10 per exposure group) were exposed to 2-butoxyethanol (BE) vapors (0, 31, 62.5, 125, 250, or 500 ppm 6 h/d, 5 d/wk, for 13 weeks) to characterize its prechronic toxicity. Dental lesions consisting of bilateral multifocal dental pulp thrombosis, pulp infarction, and odontoblast infarction were noted in the maxillary incisors of 3 of 4 rats from the 500-ppm group that were sacrificed when moribund during the first week of exposure. In addition, 1 rat from the 500-ppm group that was sacrificed on day 32 had similar unilateral incisor lesions but with additional findings consistent with a unilateral maxillary incisor fracture. In contrast, rats sacrificed after 13 weeks of exposure lacked dental lesions. In conclusion, BE has the potential to cause pulp thrombosis and odontoblast infarction in female rats. The apparent variability in response to BE noted in moribund sacrificed vs terminally sacrificed rats was attributed to development of tolerance to BE-induced hemolysis and subsequent incisor regeneration.

Administration, Inhalation↗
PubMed1979

Potential inhibitors of rat tooth alkaline phosphatase studied by means of different histochemical techniques.

Two histochemical methods for demonstration of alkaline phosphatase activity, a lead pyrophosphate- anda naphtholphosphate technique, were compared. Since different results may be due to methodological differences as well as different enzyme activities, the enzymatic hydrolysis of the naphtholphosphate was visualized both by means of an azo-dye coupler and by lead-capturing of the liberated phosphate ion. Various potential inhibitors of alkaline phosphatase activity (diphosphonate, D-penicillamine, and sodium fluoride) were also tested. The use of diphosphonate and D-penicillamine resulted in inhibited or reduced staining, which could mainly be explained by an interference by these compounds with components in the incubation media rather than with the enzyme itself. The addition of sodium fluoride had no effect on the naphtholphosphate staining pattern irrespective of capturing method, whereas the odontoblastic pyrophosphate splitting alkaline phosphatase appeared to be sensitive to sodium fluoride, suggesting the presence of two alkaline phosphatases in odontoblasts.

Alkaline Phosphatase↗
PubMed1988

Localization of phosphophoryn in rat incisor dentin using immunocytochemical techniques.

We studied the distribution of the phosphophoryn present in rat incisors by immunolocalization and histochemical techniques. The polyclonal antibody used reacts with both phosphorylated and de-phosphorylated phosphophoryn. Technical problems encountered in immunostaining and in preparing sections from mineralized dentin were resolved by use of peroxidase-conjugated protein A as the "second antibody" in indirect immunostaining reactions and by surface etching of partially demineralized sections. Staining with anti-rat incisor alpha-phosphophoryn antibody showed light staining over the odontoblasts and proximal odontoblastic processes, no stain over the predentin, dense staining over the intertubular dentin, and no stain over the mantle dentin. In the intertubular dentin the stain intensity was directly related to the distribution of mineral. These findings were directly corroborated by staining with Stains All. The mineralization of dentin and the distribution of phosphophoryn within the dentin may be much less uniform than previously supposed.

Animals↗
PubMed1992

Distribution of osteonectin mRNA and protein during human embryonic and fetal development.

We investigated the temporal and spatial distribution of osteonectin during human embryonic and fetal development, using in situ hybridization and immunohistochemistry. Osteonectin gene expression was generally found in cells exhibiting high rates of matrix production/proliferation. In mineralized tissue, a strong signal was obtained in osteoblasts, odontoblasts, and chondrocytes of the upper hypertrophic and proliferative zones. Chondrocytes of the mineralized zone showed no expression throughout the different stages of development. Strong osteonectin expression was found in odontoblasts of developing teeth. In addition, osteonectin mRNA and protein were detected in several non-mineralized tissues: steroid-producing cells of the adrenal gland and the gonads, kidney (glomeruli), lung (bronchi), skin, megacaryocytes, and large vessels. Histochemistry confirmed the results and detected extracellular osteonectin in bone and in the zone of mineralized cartilage only. The localization of osteonectin in bone, cartilage, and teeth is consistent with a role in the initiation of mineralization. However, the organ-specific distribution in non-mineralized tissues suggests an important multifunction role of this protein during human development.

Abortion, Spontaneous↗
PubMed1994

Site-specific expression of mRNAs for osteonectin, osteocalcin, and osteopontin revealed by in situ hybridization in rat periodontal ligament during physiological tooth movement.

We investigated the gene expression for non-collagenous proteins in periodontal ligament (PDL) by in situ hybridization histochemistry with a non-radioisotopic probe with cRNAs for osteocalcin (Osc), osteonectin (Osn), and osteopontin (Opn) in rat maxillary dento-alveolar unit containing molars and intact PDL. A highly intense positive signal for Osn and Osc mRNAs was expressed at all distal surfaces of the interradicular septum of buccal roots of the upper second molar in 7-week-old Sprague-Dawley male rats. Cells showing positive signals for Osn and Osc mRNAs were osteoblasts and osteoprogenitor cells. The distribution of Opn mRNA-positive signal was demonstrable at the mesial surface of the interradicular septum of buccal roots, where physiological bone resorption was specifically restricted during physiological tooth movement. Opn mRNA was expressed in cells on the bone resorption surface, including osteoclasts, and osteocytes. A moderately intense positive signal for Osn mRNA was distributed in fibroblasts throughout the ligament. Odontoblasts and pre-mature odontoblasts exhibited a strong signal for Osn and Osc mRNA. Cementoblasts and cementocytes were positive for Osn, Osc, and Opn mRNAs. These findings suggest physiological roles of Osc, Osn, and Opn in bone remodeling, PDL remodeling, dentinogenesis, and cementogenesis.

Animals↗
PubMed1987

Changes in the distribution of tenascin during tooth development.

Tenascin is an extracellular matrix molecule that was earlier shown to be enriched in embryonic mesenchyme surrounding the budding epithelium in various organs including the tooth. In the present study tenascin was localized by immunohistology throughout the course of tooth development in the mouse and rat using polyclonal antibodies against chick tenascin. The results indicate that tenascin is expressed by the lineage of dental mesenchymal cells throughout tooth ontogeny. The intensity of staining with tenascin antibodies in the dental papilla mesenchyme was temporarily reduced at cap stage when the tooth grows rapidly and undergoes extensive morphogenetic changes. During the bell stage of morphogenesis, the staining intensity increased and tenascin was accumulated in the dental pulp even after completion of crown development and eruption. Tenascin was present in the dental basement membrane at the time of odontoblast differentiation. The dental papilla cells ceased to express tenascin upon differentiation into odontoblasts and tenascin was completely absent from dentin. It can be speculated that the remarkable expression of tenascin in the dental mesenchymal cells as compared to other connective tissues is associated with their capacity to differentiate into hard-tissue-forming cells.

Animals↗
PubMed2002

A mineralizing rat dental pulp cell subline expressing collagen type I and dentin sialoprotein-phosphophoryn transcripts.

A mineralizing rat dental pulp cell subclone, termed M2H4, was selected from single-cell cloning of the rat dental pulp cell line RPC-C2A by screening confluent single-cell cultures for their ability to undergo mineralization. To induce mineralization, confluent single-cell cultures were treated for 8 d with ascorbic acid followed by the addition of inorganic phosphate to a final concentration of 4 mM for an additional 3 d. Confluent M2H4 subclones were shown by immunofluorescence and electron microscopy to form collagen type I fibrils. Furthermore, using reverse transcriptase-polymerase chain reaction, this subclone was found to be capable of expressing dentin sialoprotein-phosphophoryn (DSP-PP) transcripts, an odontoblast-specific marker. Thus, this newly identified mineralizing rat M2H4 subclone possesses odontoblast-like characteristics and can serve as an in vitro model for examining the role of DSP and PP in the formation of mineralized dentin.

Animals↗
PubMed1989

Immunocytochemical localization of amelogenins in the deciduous tooth germs of the human fetus.

The immunocytochemical localization of amelogenins in the developing deciduous tooth germs of 6-month-old human fetuses was investigated by the protein A-gold method using an antiserum against porcine 25K amelogenin. The inner enamel epithelial cells and underlying matrix showed no amelogenin-like immunoreactivity. Distinct immunoreactivity was initially shown by fine fibrils found beneath the intact basal lamina of preameloblasts at the early differentiation stage. At the late differentiation stage, amelogenin-like immunoreactivity was shown by a fine granular material within the extracellular matrix as well as by the Golgi apparatus, secretory granules, lysosomal structures, coated vesicles, and coated pits of preameloblasts with a disrupted basal lamina. At the formative stage, the localization of immunoreactivity in secretory ameloblasts was similar to that in preameloblasts during the late differentiation stage. However, immunopositive coated vesicles and coated pits were only found at the early stage of matrix formation. The calcified enamel matrix and stippled material showed intense immunoreactivity. Immunocytochemical labeling of the enamel matrix appeared as a gradient, decreasing from the enamel surface to the dentinoenamel junction. No maturation stage of ameloblasts existed in the tooth germs examined. In predentin and dentin, amelogenin-like immunoreactivity was occasionally detected on odontoblasts and their processes, but odontoblasts and cells of the stratum intermedium contained no immunoreactive elements. These findings confirmed that the secretory ameloblast in the human deciduous tooth germ is responsible for the synthesis and secretion of enamel proteins.

Amelogenin↗