Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Tooth Calcification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources
PubMed1984

The formation and remineralization of artificial white spot lesions: a constant composition approach.

Artificial white spot lesions have been prepared on bovine enamel surfaces by the controlled addition of lactate buffer containing methylhydroxydiphosphonate ions. The rates of remineralization have been measured using a constant composition method in solutions of calcium phosphate of low supersaturation. Deposition of new hydroxyapatite solid phase takes place exclusively within the white spot lesion at a rate appreciably slower than that of an acid-etched enamel surface, probably due to the presence of methylhydroxydiphosphonate located within the intact surface region of the lesion.

Animals↗
PubMed1984

Acceleration of remineralization in vitro by sodium monofluorophosphate and sodium fluoride.

Sixteen groups of artificial caries lesions were treated with from 75-900 ppm F from MFP, NaF, combinations of the two, or water for five min twice daily for ten days. Between treatments, the lesions were placed in a remineralizing solution at 37 degrees C. Quantitative microradiography of the treated lesions vs. matched untreated lesions showed significant remineralization of the surface layer and lesion body of all groups, including the water-treated control group. Fluoride treatments improved remineralization. Increasing the concentration of NaF had only a small effect on remineralization, but MFP was more effective at higher concentrations. Evaluation of MFP/NaF mixtures showed that greatest remineralization was obtained from a 75/225 ppm F ratio of NaF/MFP. This combination of F- and PO3F= was more effective than a fluoride concentration of 300 ppm F from either agent alone.

Dental Caries↗
PubMed1984

In vivo remineralization of human enamel and dental calculus formation.

The aim of this investigation was to determine the inorganic composition and the surface morphology of remineralized enamel areas and of dental calculus in heavy-calculus-formers (five subjects) and to compare these results with those of non-calculus-formers (two subjects). Electron probe micro-analysis (EPMA) was carried out on sound, acid-etched, and in vivo remineralized enamel samples from heavy- and non-calculus-formers. The mean values of Ca, P, Na, Mg, Al, Si, S, Cl, and K were compared with the SEM morphology. EPMA measurements showed no significant differences in the Ca/P ratio of the surface layers of prism-oriented and/or homogeneous enamel remineralization. The variations of remineralization pattern after acid-etching are similar in teeth from heavy dental-calculus-forming patients and in teeth from non-calculus-formers. The SEM appearances of remineralized areas and of the inner surface of mature dental calculus must be considered to be totally different. The experiments carried out suggest that the remineralization of enamel is not related to the formation of calculus.

Calcium↗
PubMed1985

The extracellular matrix of the dental pulp and dentin.

The dental pulp is a loose connective tissue, characterized by its specific anatomical location. Its extracellular components are obvious subjects for study, since such components are largely responsible for the physiological properties of the tissue. Several clinically important processes occur extracellularly, e.g., defense mechanisms such as inflammatory reactions and formation of calcified tissue. The dental mesenchyme has a crucial role during early tooth morphogenesis. The dental pulp, or rather the dental papilla, seems to have only an indirect role during dentinogenesis. This review discusses proteoglycans and glycosaminoglycans, fibronectin and other non-collagenous proteins, and the different types of collagen that have been studied in pulp connective tissue. With regard to its biochemical constituents, the pulp is similar to other loose connective tissues. Collagen type I is the major fibrous component, but collagen type III also constitutes a large portion. Fibronectin is present, as is a high content of proteoglycan. In the proteoglycans, all normally occurring connective tissue glycosaminoglycans can be demonstrated. The composition of the pulpal extracellular matrix during tooth development is quite different from that of the mature tooth. Thus, it is important not to draw any too-far-reaching conclusions about the situation in human pulp from results obtained by studying pulp from animal teeth with ongoing dentinogenesis. In spite of their common ancestry, pulp and dentin differ considerably in extracellular matrix composition. Proteoglycans and collagen type I are present in dentin. No type III collagen or fibronectin can be found in the dentin, although it is present in the dental pulp.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Appearance of dentin gamma-carboxyglutamic acid-containing proteins in developing rat molars in vitro.

An in vitro model of mineralization was devised in order to study the developmental appearance of dentin gamma-carboxyglutamic acid-containing proteins (DGPs) in relation to the onset of mineralization. Maxillary third molars from 11-day-old rats were cultured with or without fetal calf serum (FCS) as modified from Navia et al. (1984). Molars were incubated without radiolabel, or with either 45CaCl2 (5 microCi/ml) for 24 hr at various stages of a ten-day culture period or [3H]-leucine (10 microCi/ml) for 24 hr at the eighth day of culture. Molars were lyophilized and extracted with 10% formic acid overnight at 4 degrees C. DGPs in extracts were detected by immunologic and chromatographic techniques; DGPs in molar sections were detected by immunolocalization using indirect immunofluorescence. Molar development was evaluated histologically using the Von Kossa staining technique. Molars cultured with FCS showed histologic evidence for mineralized dentin and enamel and a significant increase in 45Ca uptake after the sixth day in vitro. Eleven-day-old molars in vivo and molars cultured without FCS showed no evidence of the presence of mineralized tissues. [3H]-Leucine-labeled DGPs were isolated and identified by affinity and reversed-phase high-performance liquid chromatography and by gel electrophoresis from both mineralized and unmineralized molars. DGP antigens were localized immunohistochemically using rabbit anti-rat antibodies raised against a highly purified DGP preparation. In the unmineralized molar, antigenicity was seen in odontoblasts but not in predentin matrix, preodontoblasts, or in any other cell type. Antigens in the mineralized molar were localized to odontoblasts and dentin.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Carboxyglutamic Acid↗
PubMed1986

Dental fluorosis developed in post-secretory enamel.

The aim of this study was to test whether dental fluorosis can be produced by administration of chronic doses of fluoride during only the post-secretory stage of enamel mineralization. Eight control and eight experimental pigs matched by weight and litter were fed a low-fluoride diet (less than 0.05 mg F-/kg b.w. daily) from weaning to slaughter at 14 months. The test group received an oral dose of 2 mg F-/kg b.w. per day from 8 months of age. Lower fourth pre-molars were at the post-secretory stage at the start of fluoride administration (confirmed by tetracycline marker) and were just erupting at slaughter. All of the fourth pre-molar teeth from the test group developed diffuse enamel hypomineralization indistinguishable from human fluorosis. No such lesions were seen in any of the teeth from the control animals. It was concluded that enamel fluorosis may be caused by fluoride exposure in the maturation phase only. The pathogenic mechanism may be an effect either on the selective loss of protein or on the influx of mineral, both of which occur during the post-secretory or maturation stage of enamel formation.

Amelogenesis↗
PubMed1992

Labile or surface pools of magnesium, sodium, and potassium in developing porcine enamel mineral.

The present study was undertaken to assess the labile or surface pools of Mg, Na, and K ions in porcine enamel tissues at various developmental stages. The enamel samples, corresponding to the outer and the inner secretory, the early maturing, and the mature hard enamel, were dissected from the labial sides of permanent incisors of 6- to 8-month-old piglets. Each enamel sample was extracted successively with solutions of de-ionized water and 50 mmol/L Tris-4 mol/L guanidine buffer (for removal of organic matrix proteins, mainly amelogenins). The labile (free or organically bound) pools of Mg, Na, and K were assessed by the total amounts of these ionic species extracted by the water and Tris-guanidine buffer. The surface (adsorbed onto enamel mineral) pool of Mg was assessed directly by determination of the adsorption of Mg onto enamel mineral at various developmental stages. The results showed that: (i) 30-40% of the Mg in the secretory and early maturation enamel was in the surface pool (adsorbed onto the enamel mineral); (ii) 25 to 40% of the total sodium in the enamel samples was in labile forms; and (iii) most (around 70-80%) of the total potassium was readily extracted in water and appeared to originate from the enamel fluid; only marginal portions remained in the solids. The present adsorption studies also indicated that the maximum uptake of magnesium in the early maturation enamel was due mostly to an increase of the occupancy by Mg ions of adsorption sites on the crystal surfaces, which become accessible with a massive removal of enamel matrix proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗
PubMed1994

Distribution of protein kinase C alpha and accumulation of extracellular Ca2+ during early dentin and enamel formation.

Activation of the protein kinase C (PKC)-related signal transduction system has been associated with phenotypic expression in a wide variety of cell types. In in vitro studies, it has often been activated by relatively small increases in the Ca2+ concentration ([Ca2+]) in the medium. The studies reported here explored the hypothesis that localized increases in the extracellular [Ca2+] and activation of the PKC-related pathway may be involved in early dentin and enamel formation. Whole-head, freeze-dried sections through the developing molars of 5-day-old rats were evaluated by methods that localized non-crystalline Ca2+. Immunohistochemical methods were adapted for use with the freeze-dried sections, and two monoclonal antibodies were used to localize PKC alpha in the formative cells of the developing teeth. Low concentrations of extracellular Ca2+ were observed in the early, unmineralized dentin in the area of ameloblast differentiation. Increased concentrations occurred at the point of initial dentin mineralization, immediately before the beginning of enamel matrix deposition. PKC alpha was localized in the differentiating odontoblasts, at the beginning of dentin matrix deposition. It was intensely localized in the distal borders of the pre-ameloblasts, and appeared to redistribute in the cells during ameloblast differentiation. These observations suggest that local increases in the extracellular [Ca2+] and the PKC signal transduction pathway may be involved in key inductions in the early stages of dentin and enamel formation.

Ameloblasts↗
PubMed1994

Induction of dentin formation on canine amputated pulp by recombinant human bone morphogenetic proteins (BMP)-2 and -4.

Dental pulp cells have the potential to differentiate into odontoblasts. The molecular mechanisms underlying differentiation are not clear. Demineralized dentin matrix is osteoinductive and contains bone morphogenetic protein (BMP) activity. BMPs have been implicated in embryonic odontogenic differentiation and hence may play a role in the differentiation of adult pulp cells into odontoblasts during pulpal healing. This study examined the hypothesis that BMPs induce dentin formation on amputated canine pulp. Recombinant human BMP-2 and BMP-4 were capped with inactivated dentin matrix on amputated pulp. At two months, the amputated pulp was filled with tubular dentin in the lower part and osteodentin in the upper part. The amount of dentin formed was markedly diminished when dentin matrix alone was implanted. These findings imply that recombinant human BMP-2 and BMP-4 induce differentiation of adult pulp cells into odontoblasts. Thus, BMPs may have a role in dentistry as a bioactive pulp-capping agent to induce dentin formation.

Animals↗
PubMed1994

Formation of afibrillar acellular cementum-like layers induced by alkaline phosphatase activity from periodontal ligament explants maintained in vitro.

Fibroblasts of the periodontal ligament, by their alkaline phosphatase (ALP) activity, are considered to play a role in the formation of acellular cementum. As a means of exploring this hypothesis, periodontal ligament explants from rat incisors were cultured in direct contact with bovine dentin slices in the presence of 10 mmol/L beta-glycerophosphate. Periosteal and pericardial tissue explants were maintained under similar conditions. After two weeks, the slices were harvested and processed for electron microscopic examination. Controls included periodontal ligament explants to which the ALP-inhibitor levamisole was added. The results suggest that only ALP-positive cultures from periodontal ligament and periosteum form mineralized layers along the dentin. After demineralization, layers consisted of fine filamentous or granular material of moderate electron-density and resembled afibrillar acellular cementum. Our findings support the hypothesis that periodontal ligament fibroblasts, by means of their ALP activity, play a pivotal role in the formation of acellular cementum.

Alkaline Phosphatase↗
PubMed1995

Problems associated with estimation of net calcium uptake during enamel formation using 45Ca.

45Ca uptake in mineralizing tissues may occur by net Ca uptake or by isotopic exchange. It is rarely possible to differentiate between these effects, making interpretation of the findings difficult. Unfortunately, this problem is not often considered, and 45Ca uptake is usually regarded as representative of only net calcium uptake. The study reported here was undertaken to estimate the extent to which 45Ca uptake in mineralizing enamel is due to net Ca deposition or to isotopic exchange, and to consider the implications. The enamel surfaces of the lower incisors of adult rats were notched at the gingival line, and the eruption distance over 16 hours was measured. This distance was used to establish the position of a 0.3-mm-wide increment of enamel at the beginning and end of the 16-hour period, during which it passed through the early-maturation stage of enamel formation. The rate of Ca uptake was determined by chemical assay. Other rats were injected with 45Ca, mean plasma specific activity values for the experimental period determined, and the rate of Ca uptake through the same area of enamel formation was estimated. The estimates were from two- to nearly ten-fold greater than those established by chemical assay, indicating that from 50 to 90% of the 45Ca uptake occurred by isotopic exchange. 45Ca uptake may indicate more about the labile state of Ca in mineralizing enamel than about the rate of mineral deposition.

Amelogenesis↗
PubMed1995

Evidence that high-sucrose diet reduces dentin formation and disturbs mineralization in rat molars.

In addition to its caries-promoting effect, a high-sucrose diet reduces the apposition of mineralized dentin in young rats. This study was undertaken to test whether it has a similar effect on the width of the as-yet-uncalcified matrix, predentin. Female Wistar rats were weaned at the age of 3 weeks and fed for 7 weeks with either a high-sucrose diet, a non-cariogenic raw potato starch diet, or a non-cariogenic commercial powdered rat food (for reference). The sucrose diet induced the greatest number of caries lesions. Dentin formation was smaller and the predentin zone wider in rats fed a sucrose diet when compared with rats fed the reference diet. In rats fed a starch diet, dentin formation was smaller than in rats fed a reference diet, but no alterations in the areas of caries lesions or predentin width were observed. Widening of the predentin zone in rats fed a high-sucrose diet may reflect changes in odontoblast function, such as reduced matrix synthesis and possibly disturbed mineralization. Dentinal caries progression may thus be modulated by odontoblast function, not as much by matrix formation but rather by mineralization.

Analysis of Variance↗
PubMed1996

Electrophoretic gels of dentin matrix proteins as diffusion media for in vitro mineralization.

Non-collagenous proteins of dentin and bone have important effects on mineralization which have been studied by various in vitro systems. We developed an in vitro mineralization system using electrophoretic gels as diffusion media of calcium and phosphate ions. Calcium and phosphate ions were diffused naturally or propelled by electric potential. Calcium phosphate was precipitated in the gel, and the precipitation was affected by proteins in the gel which had been separated by electrophoresis. We applied this system to analysis of non-collagenous proteins of dentin. Among the proteins, phosphophoryns promoted calcium phosphate precipitation in the natural-diffusion system. A non-collagenous protein having a molecular mass of 60 kDa inhibited precipitation. The results were different, however, in the electric-diffusion system, in which phosphophoryns had a negative effect. The present system enabled us to compare the effects of plural proteins rapidly, even using unpurified material.

Animals↗
PubMed1997

High resolution electron microscopy: structure and growth mechanisms of human dentin crystals.

Biological crystal formation was postulated to begin by a nucleation process. Such processes have been demonstrated for human amelogenesis and bone mineralization. The aim of this study was to confirm if such mechanisms occur during dentin crystal formation. The structure of human fetal dentin crystals and the earliest stages of mineral growth were followed by High Resolution Electron Microscopy (HREM) associated with digitalized image analysis. Micrographs of the mineralization front were first digitalized, and selected areas were transformed in the reciprocal space by Fast Fourier Transform. The resulting diffractograms were compared with computer-simulated diffractograms and used to determine the orientation of crystals. Dentin crystals, found close to the mineralization front, show a structure closely related to that of hydroxyapatite (HA), as determined by comparison of HREM images with simulated images. These crystals present numerous structural defects such as dislocations and grain boundaries. These defects appear to be present in dentin crystals at an early stage of growth. We have also observed nanometer-sized particles in mineralization areas. Calculated diffractograms of these areas show significant similarities with HA diffraction patterns, and in one case, their structure could be correlated to HA structure through an image simulation process. These nanometer-sized particles could be related to the nucleation process, and their growth, orientation, and formation appear to be mediated by extracellular matrix components.

Crystallization↗
PubMed1998

Potassium is involved in apatite biomineralization.

The biogenetic formation of mineral crystals, one aspect of biomineralization, is a multistep process of apatite formation throughout the growth of dentin tissue. An important step is the transformation of the non-mineralized predentin matrix to mineralizing dentin matrix and its biological control. In this study, the high capacity of elemental mapping is combined with single x-ray point measurements to elucidate whether special elements are involved in initiation or regulation of mineral nucleation. Directly at the mineralization front, micro-areas with a strong co-enrichment of phosphorus (e.g., as phosphate) and potassium are found. During the beginning of the calcium enrichment and the subsequent apatite mineral formation in the characteristic micro-areas, the content of potassium decreases significantly. These findings indicate that potassium is involved in the process of dentin mineralization.

Animals↗