Three categories of precursor cells have been identified in postnatal mammals: tissue-committed progenitor cells, germ layer lineage-committed stem cells and lineage-uncommitted pluripotent stem cells. Progenitor cells are the immediate precursors of differentiated tissues. Germ layer lineage stem cells can be induced to form multiple cell types belonging to their respective ectodermal, mesodermal, and endodermal embryological lineages.
View Article and Find Full Text PDFThe objectives of this study were to prepare hybrid and surface-modified amorphous calcium phosphates (ACPs) as fillers for mineral-releasing dental composites, and determine whether the mechanical strength of the composites could be improved without decreasing their remineralization potential. ACP was hybridized with tetraethoxysilane or zirconyl chloride and surface-treated with 3-methacryloxypropoxytrimethoxy silane (MPTMS) or zirconyl dimethacrylate (ZrDMA). Composites fabricated with unmodified ACP (u-ACP), hybrid or surface-modified ACP filler and photo-activated Bis-GMA, TEGDMA and 2-hydroxyethyl methacrylate (HEMA) (BTH resin), Bis-GMA, TEGDMA, HEMA and MPTMS (BTHS resin) or Bis-GMA, TEGDMA, HEMA and ZrDMA (BTHZ resin) were tested for their remineralizing potential and biaxial flexure strength (BFS).
View Article and Find Full Text PDFJ Res Natl Inst Stand Technol
July 2016
Amorphous calcium phosphate (ACP), a postulated precursor in the formation of biological hydroxyapatite, has been evaluated as a filler phase in bioactive polymeric composites that utilize dental monomers to form the matrix phase on polymerization. In addition to excellent biocompatibility, these composites provided sustained release of calcium and phosphate ions into simulated saliva milieus. In an effort to enhance the physicochemical and mechanical properties and extend the utility of remineralizing ACP composites to a greater variety of dental applications, we have focused on: a) hybridizing ACP by introducing silica and/or zirconia, b) assessing the efficacy of potential coupling agents, c) investigating the effects of chemical structure and compositional variation of the resin matrices on the mechanical strength and ion-releasing properties of the composites, and d) improving the intrinsic adhesiveness of composites by using bifunctional monomers with an affinity for tooth structure in resin formulations.
View Article and Find Full Text PDFThe goal of this study was to determine the effect that silica and zirconia have on the stability of bioactive amorphous calcium phosphate (ACP) mineral, i.e., in retarding its transformation to hydroxyapatite (HAP).
View Article and Find Full Text PDFACP is a unique calcium phosphate in that it lacks long-range crystalline order. Yet the constancy in the composition of ACP over a wide range of solution conditions suggests a well-defined local structural unit. Although this order within disorder is the most distinguishing feature of ACP, the solution instability of ACP and its ready transformation into crystalline phases such as OCP and apatite may be of greater biological relevance.
View Article and Find Full Text PDFAmorphous calcium phosphate (ACP)-filled methacrylate composites were recently found to effectively remineralize in vitro caries-like enamel lesions. Their inferior mechanical properties compared to glass-filled composites, however, limit their use as a dental restorative material. In this study, the feasibility of introducing glass-forming elements (tetraethoxysilane or zirconyl chloride) during the low-temperature synthesis of ACP was investigated.
View Article and Find Full Text PDFCalcif Tissue Int
June 2000
Comparatively little is known of the role tissue fluid electrolytes have in establishing the size and shape of apatite crystals deposited in skeletal tissues. In vitro accretion experiments using synthetic apatite seed crystals comparable in size to bone apatite were performed to assess the extent to which these crystalline features may be affected by direct electrolyte/mineral interactions. A constant composition method was used to maintain the accretion reactions under physiological-like solution conditions (1.
View Article and Find Full Text PDFObjectives: The aim of this study was to determine whether amorphous calcium phosphate (ACP)-containing composites, which have the ability to release mineralizing levels of Ca and PO4 ions, have appropriate mechanical properties for use as base and lining materials.
Methods: Composites of pyrophosphate-stabilized ACP particulates (mass fraction of 40%) and photo-activated methacrylate resins (mass fraction of 60%) were tested for biaxial flexure strength (BFS), diametral tensile strength (DTS), and compressive strength (CS). Hydroxyapatite (HAP; mass fraction of 40%), and micro-sized glass (mass fraction of 50%) composites as well as a commercial visible light curable base/liner were also tested.
Calcif Tissue Int
September 1998
In adult human bone, fluoride uptake is accompanied by an increase in apatite crystal size. This increase, however, is not isotropic but is restricted primarily to growth in width and/or thickness, with no measurable change in length. In the present study, seeded growth experiments were conducted in vitro to determine whether this anisotropic effect is physicochemical in origin, i.
View Article and Find Full Text PDFBone sialoprotein is a small, sulfated, and phosphorylated integrin-binding glycoprotein apparently found only in tissues that eventually mineralize. Nondenatured bone sialoprotein (BSP) purified from rat osteosarcoma cell line (UMR 106-01 BSP) culture media is shown to have a hydroxyapatite Kd approximately 2.6 x 10(-9) M, perhaps the strongest affinity for this mineral of any of the matrix proteins.
View Article and Find Full Text PDFObjectives: The rationale for this study was based on the hypothesis that the mechanical strength of methacrylate composites containing the bioactive filler, amorphous calcium phosphate, can be enhanced by synthesizing this filler in the presence of glass-forming agents. Specifically, this study was conducted to prepare composites with zirconia- and silica-modified amorphous calcium phosphate fillers, and to determine whether the remineralization potential from the release of calcium and phosphate ions and the mechanical properties of the corresponding methacrylate composites were enhanced.
Methods: The modified amorphous calcium phosphates were synthesized at pH 10.
Recent studies show that methacrylate-based composites with amorphous calcium phosphate (ACP) as a filler can release supersaturating levels of calcium and phosphate ions in proportions favorable for apatite formation. These findings suggest that such composites could be effectively used as coatings for remineralizing teeth damaged by tooth decay. To examine this hypothesis, we tested composites in vitro for their efficacy to remineralize artificially formed caries-like lesions in extracted bovine incisors.
View Article and Find Full Text PDFObjectives: We analyzed bladder calcifications occurring after photodynamic therapy administered for the treatment of superficial bladder cancer, a finding not previously reported after this treatment.
Methods: Bladder biopsies from 20 patients undergoing photodynamic therapy were evaluated. Bladder calcifications were identified in 2 patients and analyzed for composition.
Calcif Tissue Int
May 1996
The effects of a series of novel phosphonates on the kinetics of mineral development in an ionophore-primed 7:2:1 phosphatidylcholine (PC): dicetylphosphate (DCP): cholesterol (Chol) liposomal model system are reported. When present at 2.5 micromol/liter or 25 micromol/liter concentrations in the solution surrounding the liposomes, the investigated phosphonates did not significantly delay the initial formation of hydroxyapatite-like calcium phosphate salts (HAP) within the liposomes or the penetration of HAP crystals through the enclosing membranes.
View Article and Find Full Text PDFThis study evaluated a rapid biomineralization phenomenon exhibited by an osteoblastic cell line, UMR 106-01 BSP, when treated with either organic phosphates [beta-glycerophosphate (beta-GP), Ser-P, or Thr-P], inorganic phosphate (P(i)), or calcium. In a dose-dependent manner, these agents (2-10 mM) stimulated confluent cultures to deposit mineral in the cell layer (ED50 of approximately 4.6 mM for beta-GP (30 +/- 2 nmol Ca2+/microgram DNA) and approximately 3.
View Article and Find Full Text PDFEffects of solution calcium ions on hydroxyapatite (HAP) formation from the hydrolysis of dicalcium phosphate anhydrous (DCPA) were investigated under controlled solution conditions. The hydrolysis experiments (2.5 mmol DCPA/250 mL) were carried out at fixed pH in the absence or presence of CaCl2 (0-200 mmol/L) by standard pH stat techniques at 37 degrees C.
View Article and Find Full Text PDFA liposome-centered endogenous precipitation method was used to investigate the effect of ultrafilterable fragments from the enzymatic digestion of rat chondrosarcoma aggrecan on the formation of insoluble calcium phosphate salts in buffered solutions at pH 7.4 and 22 degrees C. Unlike the intact aggrecan and its major chondroitin sulfate and core protein components, disaccharide units from chondroitinase degradation of the aggrecan and small (< 3 kg/mol molecular weight) fragments from protease digestion of the core structure were found to be only weakly inhibitory toward mineral formation.
View Article and Find Full Text PDFThe bisphosphonate, 1-hydroxyethylidene-1,1-bisphosphonate (HEBP), was examined for its effect on calcium phosphate precipitation in pH 7.4, 22 degrees C suspensions of 7:2:1 PC:phosphatidylcholine (PC):dicetylphosphate (DCP):cholesterol (Chol) and 7:1:1 PC:phosphatidylserine (PS):Chol liposomes. HEBP (0.
View Article and Find Full Text PDFThe importance of supersaturation in the dynamics of apatite precipitation from aqueous solutions is well-established. To determine whether this parameter has a comparable impact on the concomitant development of the textural properties of this phase, such as crystal size and shape, we investigated mineral accretion in synthetic solutions seeded with 0.67 g/L apatite over a range of supersaturations at pH 7.
View Article and Find Full Text PDFObjectives: The purpose of this study was to gain a better understanding of the integration of calcium phosphate cement (CPC) implants in biological tissue.
Methods: An in vitro continuous flow system was employed to examine the protracted behavior of disc-shaped specimens of this bioactive material under sustained physiological-like solution conditions. Weight measurement, diameteral tensile strength measurement (DTS), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and powder x-ray diffraction (XRD) were used to characterize the CPC samples as a function of immersion time.
Weanling specific pathogen-free Osborne-Mendel rats were fed a high-calcium, high-phosphorus diet with various levels of sucrose and inoculated with Streptococcus sobrinus strain 6715-13WT and Actinomyces viscosus strain OMZ-105 in order to determine whether calculus and caries could develop simultaneously. Rats consumed diets designated RC-16-5, RC-16-25, or RC-16-50 which partially replaced the corn starch component with progressively higher levels of sucrose, thus, to 5, 25, or 50% sucrose. In general, bacterial recoveries of A.
View Article and Find Full Text PDFIn cortical bone samples from patients with osteogenesis imperfecta (OI), the concentrations of hydroxypyridinium cross-linking amino acids in collagen were measured by reversed-phase HPLC and the x-axis crystallinity of the apatite mineral phase was determined by x-ray diffraction. Bone samples from three patients with type I, nine patients with type III, and eight patients with type IV OI were analyzed and compared with human bone from nine controls. The concentration of the two chemical forms of the mature collagen crosslinking amino acids, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), and the ratio HP/LP were found to be alike in bone collagen of OI patients and healthy controls.
View Article and Find Full Text PDFJ Biomed Mater Res
February 1993
The quantitative deproteination of calcific deposits from surgically explanted heart valve bioprostheses was carried out by both hypochlorite and hydrazine extraction to establish which is the better procedure for preparing purified mineral suitable for detailed chemical and structural characterization. Hypochlorite treatment resulted in a material with a higher Ca/PO4 ratio than that of the untreated deposits. The hydrazine treatment did not produce such an effect.
View Article and Find Full Text PDF