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Biomedical subjects

K de Groot

Publications and source records attributed to K de Groot.

At least 199 records · Page 11Linked to original sources
PubMed1980

Interaction of some serum proteins with hydroxylapatite and other materials.

In order to investigate whether the immune system is involved in the degradation of hydroxylapatite as implant material the adsorption behavior of several serum proteins to hydroxylapatite was studied and compared with the adsorption to other calcium phosphate compounds (Ca3(PO4)2, CaHPO4), calcium carbonate, aluminium oxide, and zinc oxide. It was found that complement factors, C4 and C3, and alpha 2-HS-glycoprotein adsorbed to the calcium phosphate compounds, but not to the other materials. IgG and albumin were adsorbed to all investigated compounds. These results suggest that the complement factors are directly adsorbed on the surface of the calcium phosphate compounds. Therefore, the activation of complement, if any, proceeds by the classical pathway. The binding of complement factors to the calcium phosphate salts investigated points to a more specific involvement of the immunosystem in the degradation process of calcium phosphate implants.

Adsorption↗
PubMed1980

Tissue response to dense apatite implants in rats.

Dense (97-99.9%) hydroxylapatite ceramics were implanted in muscle and bone tissue of rats. The aim of this study was to compare apatite implant material made of commercially available powder with laboratory powder prepared in a painstaking manner. Biocompatibility, biostability, and adherence to bone were evaluated. In muscle tissue the implants were found to be encapsulated with a very thin connective tissue layer. Implantation in excavated bone tissue resulted with new bone directly deposited against the implant surface, irrespective of the type of hydroxylapatite used. When the implants were protruding from the bone surface, bone appeared to grow up to the edge of the protruding part of the implant. A very strong bonding developed; push-out tests indicated that the bone fractured but never at the interface. Histologic studies proved that a sleeve of newly formed bone closely encased the implant, regardless of shape. It was concluded that dense apatite ceramics are fully compatible with the tibia of the rat and that no degradation of the implant material occurred for intervals of up to 6 months after implantation. The very strong bonding without mechanical retention indicated continuity between artificial hydroxylapatite and natural bone. No difference was found between the biological behavior of the hydroxylapatites prepared from commercial or laboratory starting powders.

Animals↗
PubMed1980

Bioceramics consisting of calcium phosphate salts.

After a discussion of the chemical considerations involved in the production of calcium phosphate ceramics, animal and clinical studies are reviewed. Specific conclusions are that although these ceramics have high compressive strengths, they are not suitable for joint replacements. Prevention of alveolar ridge resorption is a promising concept, and space-filling and use of aids for jaw-bone enlargement are proposed for routine clinical application.

Biocompatible Materials↗
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↗
PubMed1979

Immediate dental root implants from synthetic dense calcium hydroxylapatite.

In this article, root implants implanted directly after extraction of the natural teeth were described. The root implants were made of densely sintered or hot-pressed calcium hydroxylapatite (CHA). The significance of using such implants as a method of preserving the bulk of the alveolar ridge and as possible anchoring sites for a post and core for fixed partial dentures was discussed.

Alveolar Process↗
PubMed1977

Tri-calcium phosphate as a bone substitute.

Strong porous tri-calcium phosphate ceramic has been fabricated, and investigated as a bone implant material. No foreign body reaction was observed, while osteoclastic activity was shown to be involved in biodegradation. Bone mineral was deposited directly onto the surface of the ceramic implant.

Animals↗
PubMed1975

The subcutaneous implantation of xenogeneic decalcified teeth.

Decalcified matrices obtained from bone and dentin have been used in xenogeneic implantation experiments. It is observed that such implants generally do not induce new bone but in many cases result in recalcification of old matrices. Treatment of the matrices with the enzyme inhibitor, iodoacetic acid, prior to implantation also did not enhance or improve the osteoinductive potentiality of these matrices. It is therefore suggested that the bone morphogenetic protein (BMP) to which the osteoinductive potentiality has been attributed by Urist et al. is a highly species-specific moiety and that the xenogeneic implant is hence a poor choice for its determination.

Abdomen↗