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Type I collagen regulated dentin matrix protein-1 (Dmp-1) and osteocalcin (OCN) gene expression of rat dental pulp cells.

In this study, we investigated the effect of type I collagen on dentin matrix protein-1 (Dmp-1) and osteocalcin (OCN) gene expression of dental pulp cells. The mRNA level of Dmp-1 gene was down-regulated; however, OCN gene expression was up-regulated by the culture of dental pulp cells with type I collagen. These findings imply that type I collagen regulates mRNA level of Dmp-1 and OCN gene that are predominantly expressed in active odontoblasts. The change of gene expression by type I collagen was suppressed by the blocking of collagen-integrin interaction. We could conclude that the effect of type I collagen was mediated via binding of collagen to integrin receptors.

Alkaline Phosphatase↗

[Effects of CO2 laser irradiation on microstructure of dentin, dentin adhesion of resin composites and dental pulp].

This study was designed to investigate the effects of CO2 laser irradiation on the dentin microstructure, dentin adhesion of resin composites and dental pulp. An artificial caries lesion was produced on the bovine dentin, immersing in 0.4 mol/l acetic acid. Three kinds of dentin (sound dentin, outer or inner caries dentin) surfaces were pretreated by the laser irradiation, acid etching or no-treatment. The tensile adhesion-test of these pretreated dentin surfaces was performed. The changes in these dentin surfaces by the various treatments including the laser irradiation and the resin-dentin interfaces were examined by the SEM. Furthermore, histopathological study using monkey teeth was conducted to examine the effect of the laser irradiation on the dental pulp. Histopathological changes in the pulp were found at 3 and 90 days after the operation. The findings were as follows: 1. The outer highly and inner partially decalcified layers produced in the bovine dentin were each approximately 200 microns in thickness. 2. The bond strength of the resin composites to the laser pretreated sound dentin was approximately 40 kgf/cm2. Those of the laser pretreated outer and inner decalcified dentins were about 60 kgf/cm2. 3. At the initial stage, the laser irradiation (output power 3W : irradiation period 0.5 second) exhibited a slight pulpal response, producing irritation dentin formation in the latter stage without any severe histopathological change.

Adhesiveness↗

[Effect of catecholamines and their antagonists on the responses of the dental areas of the cerebral cortex evoked by dental pulp stimulation in the rabbit].

The primary responses of the dental areas of the brain cortex in anesthetized rabbits were recorded to demonstrate that application of the alpha-adrenomimetic noradrenaline and beta-adrenolytic propranolol to the cortex suppressed, while application of the beta-adrenomimetic isadrin and alpha-adrenolytic phentolamine potentiated the electrical responses to nociceptive stimulation of the dental pulp. It was found that phentolamine exerted dissimilar effects.

Animals↗

Treatment of inflamed ferret dental pulps with recombinant bone morphogenetic protein-7.

Recombinant human BMP-7 (bone morphogenetic protein-7, osteogenic protein-1) is osteogenic, dentinogenic and cementogenic when implanted into the appropriate tissue in vivo. However, most studies characterizing the induction of these tissues have implanted BMP-7 into freshly surgerized, clinically healthy tissues. To determine if BMP-7 is dentinogenic in inflamed dental pulps, we applied BMP-7 to inflamed ferret pulps. A single application of 5 microg of a commercial preparation of lipopolysaccharide (LPS) from Salmonella typhimurium directly to the coronal pulp induced a reversible mixed inflammatory exudate of moderate intensity within 3 d. Treatment with a single application of 2.5, 7.5 or 25 microg recombinant human BMP-7/mg collagen (2 mg total mass/tooth) induced reparative dentinogenesis in controls but not LPS treated dental pulps. These data reveal that a single application of up to 50 microg/tooth of exogenous recombinant BMP-7 is insufficient to induce reparative dentinogenesis in ferret teeth with reversible pulpitis. Given that pulp cells in the inflamed tissues likely retain the capacity to respond to exogenous BMP-7, it is possible that insufficient active recombinant protein is available to induce tissue formation in experimentally inflamed dental pulps.

Animals↗

Effect of bacterial products on inflammatory reactions in the dental pulp.

Culture filtrates (extracellular components) and material obtained from disintegrated cells (intracellular components) of cultured plaque bacteria were studied for their capacity to induce inflammatory reactions in the dental pulp. Class V cavities were prepared on the buccal surface of 94 teeth: 42 test and 52 control teeth in six adult monkeys. lyophilized bacterial components were sealed into the test cavities either alone or following an 8-h topical application of a solution of the same components in phosphate-buffered saline (PBS). Culture medium and PBS were applied in two sets of control cavities. A third set was restored with zinc oxide-eugenol cement. The animals were killed 32 h after the initiation of the experiment and the pulps were examined histologically. Teeth treated trophil leukocytes in the area of the pulp subjacent to the cut dentin tubules. Abscess formation was frequently found. The severe reactions which developed were independent of differences between individual animals and differences in thickness of the remaining dentin. The controls showed damage to the odontoblasts but little or no neutrophil infiltration. The findings confirm that products of bacteria applied to exposed dentin initiate inflammatory reactions in the dental pulp.

Animals↗

Identification of alpha 2 adrenoceptors in the blood vessels of the dental pulp.

Using selective agonists and antagonists of alpha2 adrenoceptors, attempts were made to identify the subtype alpha2 adrenoceptors in the blood vessels of the canine dental pulp. In chloralose-anaesthetized dogs, intra-arterial administration of noradrenaline and guanabenz in different doses produced a dose-related pulpal vasoconstriction which was measured using hydrogen-gas clearance. The vasoconstrictor response to noradrenaline was inhibited by phentolamine, a non-selective alpha adrenoceptor antagonist. The response to guanabenz was inhibited by rauwolscine, a highly selective alpha2 adrenoceptor antagonist. The results demonstrated that alpha2 adrenoceptors are present in the blood vessels of dog dental pulp.

Animals↗

The turnover of collagen in the dental pulp of rat incisors.

The turnover of collagen in the dental pulp was studied using H3-proline and microchemical techniques. The incorporation of label into the whole tissue was very high, with most of the label being incorporated into the noncollagenous substances. The rate of disappearance of label from collagen approximated the disappearance of label from noncollagenous components, suggesting that the whole pulp was undergoing rapid remodeling. There seems to be more than one metabolic pool of collagen.

Animals↗

Effects of 5-fluorouracil on mitogen-induced costimulatory capacity of accessory cells from rat oral mucosa and dental pulp.

The present study was designed to investigate the effect of the antimetabolite 5-fluorouracil (5-FU) on the capacity of the oral epithelium and the dental pulp to induce a mitogen-driven T-cell proliferation. Inbred Lewis rats were given 6 i.v. injections of 5-FU (30 mg/kg or 50 mg/kg) over a period of 8 days. Suspensions of oral epithelial and dental pulpal cells were prepared. The costimulatory capacity of the accessory cells from treated animals was monitored by their ability to induce a mitogen (ConA)-mediated proliferation of T cells isolated from regional lymph nodes of untreated animals. Accessory epithelial cells from rats treated with the high dose of 5-FU, but not the low dose, induced a decreased T-cell proliferation compared to controls. Accessory pulpal cells from rats, treated with 30 mg/kg or 50 mg/kg of 5-FU, induced a lower T-cell proliferation. When MHC class II molecule depleted T-cell suspensions from lymph nodes of 5-FU-injected animals were incubated with ConA, a significant proliferative response was observed. This finding correlated with an increase of MHC class II molecule expressing cells detected after incubation, although no such cells were observed immediately following the initial purification step of T cells. This finding demonstrates that the accessory cells could partly restore their expression of MHC class II molecules during incubation. The results of the study suggest that the function of immunocompetent cells of the oral mucosa and dental pulp is influenced by treatment with 5-FU and that the function of accessory cells of the pulp is affected more than the function of accessory cells derived from the oral mucosa.

Animals↗

Secretoneurin, a novel neuropeptide, in the human dental pulp.

Secretoneurin is a neuropeptide that is stored in and released from primary afferent neurones. By radioimmunoassay and immunohistochemistry, secretoneurin was here demonstrated in the human dental pulp and localized in varicose nerve fibres that were frequently associated with blood vessels. No significant correlation was found between the levels of immunoreactive secretoneurin and immunoreactive calcitonin-gene related peptide. The results suggest that primary afferent neurones of the human dental pulp contain secretoneurin, which may influence local inflammatory responses if it is released together with other neuropeptides.

Adolescent↗

Effects of parathyroid hormone, 1,25-dihydroxyvitamin D3, and prostaglandin E2 on alkaline phosphatase activity in cultured dental pulp and gingiva cells of bovine calf.

The effects of parathyroid hormone (PTH), 1,25-dihydroxyvitamin D3, and prostaglandin E2 (PGE2) on alkaline phosphatase activity on cultured dental pulp and gingiva cells of bovine calf were compared. In pulp cells, PTH, 1,25-dihydroxyvitamin D3, and PGE2 significantly increased alkaline phosphatase activity, but no increase in the enzyme activity by these factors was observed in gingiva cells. Dibutyryl cAMP also increased alkaline phosphatase activity in both types of cell, but the increase in pulp cells was greater than that in gingiva cells. Treatment of the cultured pulp cells with PTH or PGE2 significantly increased the intracellular cAMP content. These results suggest that calciotropic factors such as PTH, 1,25-dihydroxyvitamin D3, and PGE2 may be involved in the differentiation of dental pulp cells and that some of these effects (those of PTH and PGE2) are mediated by cAMP.

Alkaline Phosphatase↗

Vasodilatation in the dental pulp produced by electrical stimulation of the inferior alveolar nerve in the cat.

The effects of nerve stimulation on blood flow were studied in the dental pulp of anesthetized cats. Changes in iodide disappearance rate (k-value) from dentinal cavities were used to determine changes in pulpal blood flow. Electrical stimulation of the distal end of the cut inferior alveolar nerve after alpha-adrenoceptor blockade (phentolamine, 3 mg/kg) consistently resulted in a rapid increase in disappearance rate. The first stimulation produced the greatest response (an average increase in k-values of 60%) and repeated stimulations showed a successive attenuation in response, the fourth stimulation usually having no effect. A progressive decrease in resting k-values was observed after the first stimulation, indicating an impaired exchange function of the capillary vessels. Systemic pretreatment with propranolol (0.5--1 mg/kg), atropine (3 mg/kg), mepyramine (3 mg/kg) and cimetidine (3 mg/kg) did not influence the rapid increase in k-values produced by the nerve stimulation. The experiments show that vasodilatation in the cat dental pulp produced by stimulation of the inferior alveolar nerve is not mediated by common efferent vasodilatory mechanisms and strengthen the hypothesis that the sensory nerve axon reflex mechanism is involved.

Animals↗