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At least 1,063 records · Page 59Linked to original sources
PubMed1982

Adsorption thermodynamics of acidic proline-rich human salivary proteins onto calcium apatites.

The thermodynamics of adsorption of four acidic proline-rich salivary proteins from their aqueous solutions onto hydroxyapatite (HA) and fluorapatite (FA) have been analyzed. Enthalpies and entropies of adsorption were derived from isotherms at 37 degrees C and 4 degrees C and led to the unexpected conclusion that adsorption of the macromolecules studied is an endothermic process. Consequently, adsorption is driven by an increase in entropy. Most of this increase originates in the adsorbate molecules, probably through disruption of internal ion pairs, hydrogen bonds, and displacement of water molecules. Integral free energies of adsorption (delta G) and the partial contributions of adsorbent and adsorbate were both calculated as a function of the adsorption coverages. For equal coverages (of each adsorbate), delta G is lower with FA than with HA. Most of the contribution to delta G originates from the adsorbate, although the adsorbent contribution becomes significant as adsorption saturation is approached. The differences in the various thermodynamic quantities are qualitatively related to the known structural features of the four proteins. The results are important in understanding the role played by the proline-rich proteins in the oral environment.

Adsorption↗
PubMed1994

[Alveolar bone replacement by implantation of Ossynth and Ossnativ hydroxy apatite ceramics].

Natural and synthetic HA-granulate (made by SZIKKTI Budapest) were implanted to 91 patients by the authors with the aim of bone replacement. Follow up controls proved that the biomaterial has been incorporated without clinical symptoms and complaints in 87 percent. Biopsies taken from replacement site showed that the HAK isolated from natural substance could be incorporated into the calcified tissue and it is also able to help the formation of the new bone.

Adult↗
PubMed1993

Preparation and characterization of porous apatite ceramics coated with beta-tricalcium phosphate.

Hydroxyapatite (Ca10(PO4)6(OH)2; HA) is one of the most biocompatible materials with bones, and porous HA is promising bone substitute materials for clinical applications. While there are reports that beta-tricalcium phosphate (Ca3(PO4)2; TCP) has higher resorbability than HA when the material is implanted in a bone defect. In the present study, porous HA coated with beta-TCP was prepared by our unique method. The porous HA of about 60% porosity with interconnecting pore structure was soaked in diammonium hydrogen phosphate solution, and then the HA was sintered at 900 degrees C for 3 h. beta-TCP was revealed by X-ray diffractometry on the surface of porous HA. It was possible to control the content of surface-formed beta-TCP arbitrary by varying the concentration of the solution. The obtained HA coated with 33 wt% beta-TCP (33TCP) had about 60% open porosity with the pore size from 150 to 400 microns. The average compressive strength of this porous ceramics was 17.5 MPa. Surface coated HA with beta-TCP deprived of the brittleness in handling. The weight of HA implanted into muscles was increased obviously at 4 weeks because of formation of carbonate hydroxyapatite on the surface of HA. The weight of 33TCP was scarcely changed up to 12 weeks, but the weight tended to increase at 24 weeks. The carbonate hydroxyapatite was not formed on 33TCP at 4 weeks, but formed on it at 24 weeks. Therefore beta-TCP coated porous HA behaved like beta-TCP initially after implantation, and then behaved like HA.

Animals↗