Biomedical subjects

S De Aza

Publications and source records attributed to S De Aza.

5 recordsLinked to original sources

PubMed2000

Reactivity of a wollastonite-tricalcium phosphate Bioeutectic ceramic in human parotid saliva.

In a previous study, a new ceramic material (Bioeutectic), prepared by slow solidification through the eutectic temperature region of the wollastonite-tricalcium phosphate system, was found to be reactive in a simulated body fluid. In the present study, the reactivity of the Bioeutectic was assessed in human parotid saliva. Samples of the material were soaked for one month in human parotid saliva at 37 degrees C. The experiments showed the formation of two separate zones of carbonate-hydroxyapatite-like phase on the periphery of the samples. The first zone was formed by reaction of the bioeutectic with the saliva and progressed inside the material. The other zone developed on the surface of the bioeutectic by precipitation from the media. The mechanism of carbonate-hydroxyapatite-like phase formation in human parotid saliva appeared to be similar to that of apatite-like phase found in a simulated body fluid.

Apatites↗

PubMed2000

Morphological and structural study of pseudowollastonite implants in bone.

In vitro experiments show that pseudowollastonite (alpha-CaSiO3) is a highly bioactive material that forms a hydroxyapatite surface layer on exposure to simulated body fluid and also to human parotid saliva. This finding is very significant, as it indicates that the pseudowollastonite can be physically and chemically integrated into the structure of living bone tissue, and therefore could be suitable for repair or replacement of living bone. The physical and chemical nature of the remodelled interface between the pseudowollastonite implants and the surrounding bone has been studied after in vivo implantation of 20 pseudowollastonite cylinders into rat tibias. The interfaces formed after 3, 6, 8 and 12 weeks of implantation were examined histologically using an optical microscope and also by analytical scanning electron microscopy. SEM and X-ray elemental analysis showed that the new bone was growing in direct contact with the implants. Other examinations found that the bone was fully mineralized. The ionic exchange taking place at the implant interface with the body fluids was essential in the process of the implant integration through a dissolution-precipitation-transformation mechanism. The study found the interface biologically and chemically active over the 12-week implantation period. The rate of new bone formation decreased after the first 3 weeks and reached constant value over the following 9 weeks. The osteoblastic cells migrated towards the interface and colonized the surface at the contact areas with the cortical regions and also bone marrow.

Animals↗

PubMed1999

Bioactivity of pseudowollastonite in human saliva.

OBJECTIVES: Pseudowollastonite (CaO.SiO2) was found to be bioactive in a simulated body fluid environment. In the present study, 'in vitro' bioactivity of pseudowollastonite was further assessed in human parotid saliva. The main objective was to compare behaviour of the material in a natural medium of high protein content (human parotid saliva) with its behaviour in an acellular protein-free solution (simulated body fluid). METHODS: Samples of polycrystalline pseudowollastonite were immersed for one month in human parotid saliva at 37 degrees C. Changes in ionic concentrations in the human parotid saliva and the pH right at the interface of pseudowollastonite/human parotid saliva were determined. The products of the interfacial reactions were studied by thin-film X-ray diffraction, scanning and transmission electron microscopy. RESULTS: The results confirmed formation of a hydroxyapatite-like layer on the surface of the material, and also suggested that the mechanism of hydroxyapatite-like layer formation in saliva was similar to that showed in simulated body fluid. CONCLUSIONS: The hydroxyapatite-like layer formed at the interface was found to be compact, continuous and composed of many small crystallites with ultrastructure similar to that of natural cortical bone and dentine. The study also concluded that the high pH conditions (10.32) existing right at the pseudowollastonite/human parotid saliva interface promoted hydroxyapatite-like precipitation. At this stage of the study, similarities of the material behaviour in saliva and acellular simulated body fluid suggest that the pseudowollastonite could be of interest in specific periodontal applications for bone restorative purposes.

Body Temperature↗

PubMed1998

Analytical control of wollastonite for biomedical applications by use of atomic absorption spectrometry and inductively coupled plasma atomic emission spectrometry.

Preliminary in vitro experiments revealed that wollastonite (CaSiO3) is a potentially highly bioactive material that forms a hyroxyapatite (HA) surface layer on exposure to simulated body fluid with an ion concentration, pH and temperature virtually identical with those of human blood plasma. The formation of the HA layer is an essential requirement for an artificial material to be used as bioactive bone substitute. This finding opens up a wide field for biomedical applications of wollastonite. Biomaterials used as implants in the human body require strict control of trace elements and of the toxic species specified in American Society for Testing and Materials F-1185-88 (As, Cd, Hg and Pb) in ceramic hydroxyapatite for surgical implantation. In this work, two types of pseudowollastonite, the high temperature form of wollastonite, were analysed by using cold vapour atomic absorption spectrometry and hydride generation atomic absorption spectrometry, in order to determine the elements stated in the above-mentioned norm, and inductively coupled plasma atomic emission spectrometry to establish the SiO2/CaO ratio of the two materials and analyse for all other impurities introduced by the raw materials and by the processes of synthesis, sintering and grinding. Barium and Mg were especially prominent in raw materials, and Zr, Y, Mg, W, Co and Ni come mainly from the processing.

Barium↗

PubMed1997

Bioeutectic: a new ceramic material for human bone replacement.

In the present work, a new way of obtaining bioactive ceramic materials with eutectic morphology is presented. To this purpose the binary system wollastonite-tricalcium phosphate was selected, taking into account the different bioactivity behaviour of both phases. The material is formed by quasi-spherical colonies composed of alternating radial lamellae of wollastonite and tricalcium phosphate. In in vitro experiments the material presents a high reactivity, with the formation of two well-differentiated zones of hydroxyapatite, one formed by alteration of the eutectic material with solution of the wollastonite into the simulated body fluid and subsequent pseudomorphic transformation of the tricalcium phosphate into hydroxyapatite, and the other, in the last stages of the experiments, by deposition of hydroxyapatite onto the surface of the material. The hydroxyapatite morphology, formed at the beginning of the reaction, is similar to that of porous bone. The method used opens the opportunity to develop a new family of bioactive materials with different constituents, binary or ternary, for which the authors propose the general name of bioeutectics.

Biocompatible Materials↗