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PubMedDate not supplied

Abnormal pulp calcification in primary molars after fluoride supplementation.

Forty-five caries-free primary molars from children with continuous fluoride supplementation (n = 28) after birth and from children without fluoride prophylaxis (n = 17) were investigated by light microscopy. The following results were obtained: The prophylaxis group evidenced a special form of calcification consisting of fibrodentin-like hard tissue developing intramurally in the dentin wall especially at the pulp floor and spreading irregularily into the pulp cavity by displacing the degenerating pulp tissue (n = 24). These teeth were ankylosed in the bi- and trifurcation area as well as inside the roots. This kind of hard tissue was not observed in the teeth from untreated children. Only 5 children had greater calcifications attached at the pulp wall. Nevertheless, this difference was statistically significant (p = 0.001) and indicates a relationship between fluoride prophylaxis, the special form of pulp calcification and tooth ankylosis.

Adolescent↗
PubMed1993

Mineral-matrix interactions in bone and dentin.

The bone, dentin, and cementum of the mature individual are comprised from a dense collagenous fiber network into which the carbonate-apatite mineral phase is deposited. It is hypothesized that a set of collagen-interactive acidic phosphoproteins are secreted by the osteoblasts, odontoblasts, and cementoblasts into the preformed collagenous matrix. These proteins then interact specifically with the collagen and nucleate apatite formation on and within the fibrils. These phosphoproteins may also regulate the morphology, rate of growth, and stability of the mineral phase crystals. The acidic matrix phosphoproteins may thus be considered as the crucial regulators of mineralization and tissue stability. In the dentin system, these regulatory proteins are synthesized, posttranslationally modified, and secreted in vesicles different from the collagen secretory vesicles. Mineralization occurs as the regulatory proteins are deposited on the preformed fibrils. This model requires testing in the bone system. In dentin, in the absence of tissue turnover, the resident phosphoproteins are degraded in situ over time, perhaps changing the properties of the tissue. Regulation of synthesis, secretory pathways and retention of integrity within the matrix are thus important areas for further investigation.

Amino Acid Sequence↗
PubMed1975

Mineralization of dentin, bone and tendon in vitro.

Bovin dentin, bone and tendon slices, and rat bone, readily mineralize to variable degrees after demineralization by (EDTA) at pH 7.4, but they fail to mineralize after dimeralzation with acetic acid (HAc) at pH3.0. The demineralized dentin, but neither bone nor tendon, contained organically bound phosphate. The EDTA-demineralized dentin contained less phosphate than HAc-demineralized dentin. HAc-demineralized rat dentin contained high levels of phosphate. Since the EDTA- and HAc-demineralized rat dentin contained widely different levels of phosphate, yet both mineralized, it was concluded that phosphoprotein had little effect on nucleation. The reason why HAc-demineralized tissue other than rat dentin failed to nucleate and mineralize was not clarified.

Acetates↗
PubMed1995

Ultrastructural organic-inorganic relationships in calcified tissues: cartilage and bone vs. enamel.

Close organic-inorganic relationships exist in all calcified tissues, the inorganic substance being linked to crystal ghosts (CGs). These are organic, crystal-like structures present in areas of initial calcification. In cartilage and bone, they form aggregates with the same morphology and distribution as the calcification nodules; in enamel, they consist of long filament- and ribbon-like structures, having the same arrangement as untreated crystals. CGs of cartilage and bone are acidic structures with histochemical properties of proteoglycans; CGs of enamel probably correspond to enamelins. The close morphologic similarity between CGs and crystals suggests that the former have a role in the formation of the latter.

Bone and Bones↗
PubMed1979

Fine structural observations of calcium storage in human dental pulp cells in primary culture.

Primary culture of explants of human dental pulp tissue allows the study of the cytophysiology and differentiation of the cultured cells over a two-week period. The distribution of calcium was found in two different experimental conditions : with and without a calcium loading, by mean of a lead technique checked by microprobe analysis. The existence of two cell populations was revealed. Intra-mitochondrial ring-like granules characterize type 1 cells when overloaded, while a strong calcium storage is detected in the rough endoplasmic reticulum, Golgi apparatus and mitochondrial (without any inner organization of the deposits) of the type 2 cells. Our results also show the presence of calcium on gap-junctions (revealed) by lanthanum method), and on the extracellular matrix (collagen fibres and complex carbohydrates). The ability of some mitochondria to store calcium (ring-like granules) suggests that the type 1 cells are fully differentiated in odontoblast-like cells and perhaps engaged in mineralization processes. The calcium binding sites, localized on the extracellular matrix may therefore be considered as the earliest foci of calcification.

Calcium↗
PubMed1996

Vertebrate mineralized matrix proteins: structure and function.

The mineralized matrices of enamel, cementum, dentin, calcified cartilage and bone are similar in their ability to form a microenvironment that facilitates deposition of hydroxyapatite. However, they are not identical, as witnessed by the nature of apatite crystals that are formed. Enamel is devoid of collagen; and is composed of enamelins, amelogenins, tuftelin and ameloblastin, first described at this meeting. Cementum, dentin and bone matrices are composed primarily of type I collagen, however, each matrix may also contain unique moieties. The exact composition of cementum is not fully known, but in dentin there are unique matrix proteins, phosphophoryn (dentin phosphoprotein, DPP), a distinctive dentin matrix protein (DMP-1), and dentin sialoprotein (DSP). In bone, dentin and cementum, the matrix proteins include proteoglycans (versican, decorin, biglycan) and hyaluronan, glycoproteins which are often phosphorylated and sulfated (osteonectin, RGD-containing proteins) and gla-containing proteins (matrix gla protein, protein S, osteocalcin). The exact nature of all the non-collagenous proteins of calcified cartilage is not yet fully known. While there are no definitive functions for any of the mineralized matrix proteins to date, they most likely participate in regulation of cell metabolism, matrix deposition and mineralization, and bone turnover.

Animals↗
PubMed1976

Interrelations of matrix lipids, vesicles, and calcification.

When calcifying tissues were extracted with hot pyridine or hot benzene and then decalcified and stained with Sudan black B, the areas where mineralization was being initiated stained strongly, the rest of the calcified tissues being unstained. Histochemical methods showed that lipids were responsible for the staining. They were isolated biochemically and found to be phospholipids, very resistant to extraction before decalcification of the tissues and consisting predominantly of phosphatidyl serine and phosphatidyl inositol. It was proposed that these phospholipids were active at nucleating sites in apatite crystal formation, since it is known that phosphatidyl serine binds calcium strongly. It has been shown that phosphatidyl serine is present in matrix vesicles.

Animals↗