Search results for "apatite"

Influence of Temperature on Calcium Hydroxyapatite Nanopowders

2012

The aim of this work is to investigate the effects of thermal treatment, in the range of temperature between 80°C - 900°C, on crystallinity, morphology and particles size of calcium hydroxylapatite nanopowders (HAp). A complete study was carried out applying 31P Magic Angle Spinning NMR, X-ray diffraction, nitrogen porosimetry and Transmis- sion Electron Microscopy techniques. HAp specimens were prepared by chemical precipitation in an aqueous solution of calcium nitrate and ammonium hydrogen phosphate. The thermal treatment performed, showed the formation of crystals whose appearance has three main morphologies and different particles size. HAp treated up to 500°C showed a set of needle-li…

Bioengineering of the silica-polymerizing enzyme silicatein-alpha for a targeted application to hydroxyapatite.

2009

Since its discovery, numerous biotechnological approaches have aimed to explore the silica-polymerizing catalytic activity of the enzyme silicatein. In vivo, silicatein catalyzes polymerization of amorphous silica nanospheres from soluble precursors. In vitro, it directs the formation of nanostructured biosilica. This is of interest for various applications that strive to benefit from both the advantages of the biological system (i.e., silica synthesis under physiological conditions) and the cell mineralization-stimulating effect of biosilica. However, so far immobilization of silicatein has been hampered by the complex multistep procedure required. In addition, the chemical surface modific…

The Antimicrobial Action of Silver Halides in Calcium Phosphate

2014

Silver halides represent a yet unexplored avenue for imparting antimicrobial activity to calcium phosphates. Negtively charged silver halide colloids (AgI, AgBr and AgCl) were added to synthesized amorphous calcium phosphate. Concurrent melting of silver halides and crystallization to carbonated apatite at 700 oC increased the silver halide surface area available to bacteria and formed a lower solubility apatite. The effect of the matrix solubility on antimicrobial response could then be investigated. Pseudomonas aeruginosa was more sensitive to silver iodide and silver bromide than Staphylococcus aureus. Silver iodide demonstrated greater activity than silver bromide. Silver chloride did n…

A zinc-doped endodontic cement facilitates functional mineralization and stress dissipation at the dentin surface

2018

Objective: The purpose of this study was to evaluate nanohardness and viscoelastic behavior of dentin surfaces treated with two canal sealer cements for dentin remineralization. Material and Methods: Dentin surfaces were subjected to: i) 37% phosphoric acid (PA) or ii) 0.5 M ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite), respectively. Samples were stored in simulated body fluid during 24 h or 21 d. The intertubular and peritubular dentin were evaluated using a nanoindenter to assess nanohardness (Hi). The load/displacement responses were used f…

Characterisation of Apatites as Potential Uranium Reference Materials for Fission-track Dating by LA-ICP-MS

2015

We report homogeneity tests on large natural apatite crystals to evaluate their potential as U reference materials for apatite fission-track (AFT) thermochronology by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The homogeneity tests include the measurements of major element concentrations by electron probe microanalysis (EPMA), whereas for U concentration, isotope dilution (ID) ICP-MS and laser ablation (LA) ICP-MS were employed. Two apatite crystals are potential reference materials for LA-ICP-MS analysis: a 1 cm3 fraction of a Durango crystal (7.5 μg g−1 U) and a 1 cm3 Mud Tank crystal (6.9 μg g−1 U). The relative standard deviation (1 RSD) of the U concentrat…

Insights into the In Vitro Formation of Apatite from Mg‐Stabilized Amorphous Calcium Carbonate

2020

Bioengineered human bone tissue using autogenous osteoblasts cultured on different biomatrices

2003

Surgical treatment of critical-size posttraumatic bone defects is still a challenging problem, even in modern bone and joint surgery. Progress in cellular and molecular biology during the last decade now permits novel approaches in bone engineering. Recent conceptual and technical advances have enabled the use of mitotically expanded, bone-derived cells as a therapeutic approach for tissue repair. Using three different tissue carrier systems, we successfully cultivated human osteoblasts in a newly developed perfusion chamber. We studied cell proliferation and the expression of osteocalcin, osteopontin, bone morphogenetic protein-2A, alkaline phosphatase, and vascular endothelial growth fact…

Laser-induced time-resolved luminescence in analysis of rare earth elements in apatite and calcite

2021

Laser-induced time-resolved luminescence was used to study rare earth element (REE) containing natural apatite and calcite minerals. The luminescence from 400 nm to 700 nm in the minerals was analyzed with excitation ranges 210–340 nm and 405–535 nm. As an outcome, several useful excitation wavelengths to detect one or more REE from apatite and calcite are reported. The feasibility of selected excitations in e.g. avoiding the disturbance of intense Mn2+ luminescence band, results was demonstrated with a non-gated detector. peerReviewed

Effect of pH on compressive strength of some modification of mineral trioxide aggregate

2013

Objectives: Recently, it was shown that NanoMTA improved the setting time and promoted a better hydration process which prevents washout and the dislodgment of this novel biomaterial in comparison with WTMA. This study analyzed the compressive strength of ProRoot WMTA (Dentsply), a NanoWMTA (Kamal Asgar Research Center), and Bioaggregate (Innovative Bioceramix) after its exposure to a range of environmental pH conditions during hydration. Study Design: After mixing the cements under aseptic condition and based on the manufacturers' recommendations, the cements were condensed with moderate force using plugger into 9 × 6 mm split molds. Each type of cement was then randomly divided into three…

Computational and experimental studies of size and shape related physical properties of hydroxyapatite nanoparticles

2011

In this work, the properties of hydroxyapatite (HAP) nanoparticles (NPs) have been studied both theoretically and experimentally focusing on computational analysis. HAP is widely used to fabricate implants, for drug delivery, etc. The physical properties of the nanosized HAP particles play an important role in the interaction with cells in the human body and are of great interest. Computer simulation was employed to understand the properties of HAP clusters (Ca(5)(PO(4))(3)OH) including formation energies, dipole moments and polarization (surface charges) by molecular mechanics (MM + , OPLS) and mostly by quantum semi-empirical Hartree-Fock (PM3) methods. The size of the simulated cluster i…