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Biomedical subjects

A A Driessen

Publications and source records attributed to A A Driessen.

9 recordsLinked to original sources
PubMed1986

A comparative study of different beta-whitlockite ceramics in rabbit cortical bone with regard to their biodegradation behaviour.

Different beta-whitlockite ceramic cylinders of standard size were implanted in the tibiae of rabbits to study the influence of micropores and chemistry on the biodegradation rate. The materials were evaluated by radiography and light microscopy. Surface chemistry was varied by the addition of impurities, while different applied pressures before sintering and different sintering temperatures gave rise to different micropores. Both factors influenced the biodegradation rate.

Animals↗
PubMed1985

Interaction of biodegradable beta-whitlockite ceramics with bone tissue: an in vivo study.

The biodegradation of different porous beta-whitlockite materials are studied by in vivo experiments, radiographic follow-ups and light microscopy observations. The materials were implanted in rabbit tibiae for 16 month. Micropores play an important role in the biodegradation rate. The resorbing materials evoke an inflammation with plasma cells. The resorption starts in the medulla, and the phagocytosed particles are removed to the lymph nodes. Normal bone function can be restored after all the implant material is resorbed.

Animals↗
PubMed1985

Reconstruction of large bone defects with calcium phosphate ceramics--an experimental study.

The aim of the present study is to evaluate the bone-defect-repairing capacity of dense hydroxyapatite compared with 40% macroporous hydroxyapatite in a weight-bearing model. The experiment consisted of the production of a relatively large mid-diaphysary defect in the left femur of 18 mongrel dogs. Cylindrical and semicylindrical hydroxyapatite implants were placed in these bone defects in order to restore continuity. The biocompatibility of implanted material has been studied physiologically, by radiographs and scintigraphs, by histology and finally by biomechanical tests. The normal weight-bearing of the operated limb restored in three weeks time. There were two mechanical failures in dense cylindric implants and two in porous cylindric implants. Radiographically, no evidence was found of degradation of porous or dense implants. Radionuclide bone imaging to assess osseous changes at the site of implants, showed intense radionuclide accumulation in all recordings of porous implants up to two years after implantation, in contrast to dense implant recordings. Histologically, there was no evidence of bioresorption. The implants were in direct contact with normal bone tissue. The pores were filled by calcified bone. There were no differences between porous and dense implants concerning the biocompatibility of hydroxyapatite.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Relationship between the degradation behaviour of calcium phosphate ceramics and their physical-chemical characteristics and ultrastructural geometry.

The neck geometry of different calcium phosphate materials was studied by scanning electron microscopy. The dissolution rate of these materials, especially of the necks, was determined by chemical analysis. The degradation of calcium phosphate materials in lactate buffer, related to the detachment of sintered particles, was found to be determined by neck dissolution rate and neck geometry. The latter factor depends on the crystallography and stoichiometry of the material and the sintering conditions.

Biocompatible Materials↗
PubMed1983

Biodegradation behavior of various calcium phosphate materials in bone tissue.

In order to study the biodegradation behavior of calcium phosphate materials, cylinders of standard size were implanted in the tibiae of rabbits. Material parameters were stoichiometry (hydroxyapatite with a Ca/P ratio of 1.67 versus tricalcium phosphate with a Ca/P ratio of 1.50), crystallographic structure (apatite versus beta-whitlockite), microporosity, and macroporosity. The extent of biodegradation was evaluated by radiography, light and fluorescence microscopy, microradiography, and porosity measurements. All calcium phosphate materials were biocompatible in bone tissue. Hydroxyapatite ceramics had a higher osteogenic potential than beta-whitlockite materials. Depending on their porosities, sintered tricalciumphosphate (beta-whitlockite) materials were more or less biodegradable, in contrast to sintered hydroxyapatite materials, which showed no detectable resorption over a period of 9 months of implantation.

Animals↗
PubMed1980

Improved cements containing phosphate polymers.

The mechanical properties of two commercially available dental cements, a zinc phosphate cement and a carboxylate cement, were substantially improved by adding a polymeric phosphate acid to the cement liquids. The improvements can be explained in terms of the change in physico-chemical nature of the modified cements.

Acrylic Resins↗