PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “APATITES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 721 records · Page 40Linked to original sources
PubMed1997

Effect of calcium carbonate on clinical compliance of apatitic calcium phosphate bone cement.

Clinical requirements for calcium phosphate bone cements were formulated in terms of the initial setting time, the final setting time, the cohesion time, and the ultimate compressive strength. Two cement formulations were tested. Biocement F was made of a powder containing alpha-tertiary calcium phosphate, precipitated hydroxyapatite, and monetite. Biocement D powder also contained CaCO3. The liquid/powder (L/P) ratio of the cement paste and the accelerator concentrations (% Na2HPO4) in the cement liquid were varied. For Biocement F there was a small area of combinations of L/P ratio and percent Na2HPO4 for which all clinical requirements were satisfied. This area covered only pastes that could be applied as doughs. However, Biocement D showed a much larger area of full compliance and it covered both doughlike and injectable pastes.

Apatites↗
PubMed2000

Apatite formation on organic monolayers in simulated body environment.

Organic monolayer films with the same functional groups as collagen were prepared by a Langmuir-Blodgett (LB) method and the LB monolayers were soaked in a simulated body fluid. Nucleation of hydroxyapatite (HA) took place on the monolayers of the carboxyl group, while no nucleation occurred on the monolayers of amino groups. From IR spectra analyses it was found that an interfacial interaction between carboxyl groups and Ca ions was important for the HA nucleation, causing the formation of HA crystals from the simulated body environment.

Amines↗
PubMed2001

Apatite nucleation on silica surface: a zeta potential approach.

Zeta potential measurements on pure silica, prepared by the sol-gel method from tetraethoxysilane under acidic conditions, are reported in different suspensions. Water suspensions and suspensions containing calcium or phosphate ions with and without NaCl were tested. zeta potential measurements were carried out as a function of the pH and ion concentration. Also, calcium and phosphate adsorption on silica was determined experimentally. The results of zeta potential and adsorption measurements suggest that both calcium and phosphate ions can be adsorbed on the silica surface; however, calcium adsorption is stronger than phosphate adsorption. When calcium and sodium ions are present in the suspension, calcium adsorption decreases. It seems that certain sites on the silica surface are specific for calcium adsorption.

Apatites↗
PubMed1983

Crystal populations in human synovial fluid. Identification of apatite, octacalcium phosphate, and tricalcium phosphate.

Defatted joint fluid pellets from 4 patients with the "Milwaukee shoulder" syndrome, an aspirate of milky fluid from subcutaneous tissue of a girl with dermatomyositis/calcinosis, and 2 rabbit synovial membranes calcified by calciphylaxis were studied by Fourier transform infrared analysis. This method permits sequential electronic subtraction ("stripping") of known patterns of highly characterized reference compounds from an unknown sample pattern. Collagen and hydroxyapatite, with carbonate partially (1-3%) substituted for phosphate, and to a lesser extent hydroxyl, were found in all samples. Octacalcium phosphate (OCP) was found in all samples except that from a patient with synovial chondromatosis which contained tricalcium phosphate (TCP). Sulfate was found in 2 of the shoulder joint fluid specimens. An unidentified organic phase was present in all samples. This study confirms recent observations by others that pathologic calcifications contain several mineral phases. These data raise the possibility that hydroxyapatite nucleation may be controlled by hydrolytic alteration of precursor calcium phosphate phases such as OCP or TCP. Studies of the biologic effects of synthetic calcium phosphate crystals must take into account the existence of several crystalline phases in natural pathologic calcifications.

Animals↗
PubMed2002

In vitro characterization and in vivo properties of a carbonated apatite bone cement.

This study evaluated the in vivo behavior of an injectable calcium phosphate bone cement implanted in bone defects at the distal end of rabbit femora. After 3 weeks, samples were harvested and processed for undecalcified sectioning. Scanning electron microscopy, transmission electron microscopy, and Fourier transform infrared microspectroscopy showed direct contact of bone and cement without soft tissue interposition, biocompatibility, and bioactivity with osteoconductive properties.

Animals↗
PubMed2002

Surface structure study of biological calcium phosphate apatite crystals from human tooth enamel.

A surface-structure study of human tooth enamel crystals has been carried out by high-resolution electron microscopy (HREM). The surfaces of several crystals have been examined and the surfaces of a single crystal are described here. The observations made on this crystal are similar to the observations made on the other crystals, although the difference of morphology in the crystals observed indicates that the growth control by matrix proteins takes only place on the [011 macro 0] surfaces of the crystals. The crystal described here is oriented along the [112 macro 0] direction, and the following surfaces have been analyzed: (11 macro 00), (011 macro 1), (01 macro 11) and (0001). A subsurface reconstruction is observed just below the surface of the crystal not bonded to the matrix and lying above the supporting film. Observation of the matrix surrounding the crystal shows the existence of poorly crystalline phases with a structure close to that of hydroxyapatite (OHAP). Finally, a comparison of the images of the (011 macro 0) surface with computer-simulated images calculated for several models of the OHAP surface structure shows that the surface itself is stoichiometric and contains both calcium and phosphate groups. The knowledge of the binding sites of proteins on biomineral crystals such as the ones found in human tooth enamel is of prime importance for the understanding of their growth process. In this study, the first structure determination of the surface of human tooth enamel crystals is presented.

Apatites↗