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Biomedical subjects

A van den Hooff

Publications and source records attributed to A van den Hooff.

At least 19 recordsLinked to original sources
PubMed1990

Histological evaluation of biocompatible orthopaedic polymer.

The biocompatibility of biocompatible orthopaedic polymer implant materials was studied in subcutaneous and bony tissue of rats and rabbits. The tissue response was evaluated by histological techniques. No bone induction capacity of biocompatible orthopaedic polymer could be observed. In rabbits, the presence of plasma cells was significantly higher than in rats. The biomaterial showed some signs of biodegradation and was not very biocompatible.

Animals↗
PubMed1989

Eleven-year study of hydroxyapatite implants.

An 11-year clinical research study was conducted with both unloaded bulk hydroxyapatite implants and loaded hydroxyapatite-coated titanium implants. A total of 102 submerged bulk hydroxyapatite implants were placed after extraction of teeth to maintain the volume of the residual alveolar ridge by their physical presence. All 21 implants under fixed partial dentures and 51 of 81 implants under lower complete dentures remained submucosal. A total of 71 hydroxyapatite-coated titanium implants were connected with permucosal superstructures by use of a two-stage method. Modifications in design and in implantation technique were required. This long-term research indicates that cylindrical hydroxyapatite implants are reliable devices as natural tooth root substitutes that bond directly to bone instead of simply being osseointegrated.

Dental Abutments↗
PubMed1989

[Implants with plasma spray coatings of hydroxyapatite: an experimental study in alveolar bone].

Sintered hydroxyapatite ceramic can be coated to a titanium core by means of a high temperature plasma spray procedure. The biological response of alveolar bone to an implant with such a coating of hydroxyapatite was evaluated in an animal experimental study. The results indicated that the plasma spray coating gave a very strong and direct bonding to cortical alveolar bone. The shear strength between bone and ceramic was greater than the shear strength between ceramic and titanium. From a radiological, macroscopic and microscopic point of view the conclusion could be drawn that the biological properties of a plasma spray coating of hydroxyapatite are the same as the properties of bulk hydroxyapatite ceramic. The outermost layer of the hydroxyapatite coating appeared to be unstable under the experimental conditions.

Animals↗
PubMed1988

The healing of biologic and synthetic bone implants. An experimental study.

The aim of the present study was to investigate the osteogenic properties of different types of cancellous bone grafts inserted in large osseous defects in dogs and to compare these with those of sintered hydroxyapatite implants. Fresh cancellous autografts were rapidly revascularized and invariably induced a complete healing of the defect. Frozen and fresh cancellous allografts were largely resorbed, the latter evoking a strong antigenic response in two of the five cases. Sintered hydroxyapatite granules were largely encapsulated in fibrous tissue, neither stimulating nor inhibiting osseous ingrowth. Degradation of the hydroxyapatite implant was not observed.

Animals↗
PubMed1988

Effects of experimental defects of the articular disc of the temporomandibular joint in rats.

Triangular defects were made in different locations of the disc in rat temporomandibular joints. After 3 months the following effects were observed. Central defects had become rounded without gross changes in the mandibular head. Peripheral defects were enlarged towards the centre, occasionally accompanied by condylar hyperplasia. Microscopically the cartilagenous covering of the mandibular head in all operated cases was characterized by thickening, dispersion of cells normally closely packed in the intermediate zone, and the constant appearance of a tear parallel to the surface.

Animals↗
PubMed1986

Boiled and unboiled detached autogenous bone fragments--an experimental study.

Boiled and unboiled standardized detached bone fragments were compared in a canine model. The fragments were either left detached or fixed with a lag-screw. Additionally, various replacements were combined with transverse osteotomy followed by reduction and fixation with a six-hole neutralization plate based on the AO-principle. Follow-up was at 0-6 weeks, 6-12 weeks and 12-24 weeks. Examination of the specimens comprised radiology, histology, microradiography, fluorescence-microscopy and microangiography. Qualitative assessment indicated that boiled bone showed some delay in resorption and new bone formation when compared with unboiled bone after six weeks, but this difference was no longer discernible after 12 weeks. Semi-quantitative assessment revealed hardly any difference after six weeks. During the first few weeks, however, boiled fragments showed a clear delay of 10-14 days in resorption and new bone formation when compared with unboiled fragments. The clinical relevance is that detached bone fragments contaminated with street-refuse can be sterilized by boiling without harmful effects. Replacement of the boiled bone fragments shows a somewhat delayed, but otherwise normal resorption and new bone formation.

Animals↗
PubMed1986

Bacterially contaminated detached autogenous bone fragments--an experimental study.

Bacterially contaminated and uncontaminated standardized autogenous bone fragments were compared in an experimental canine model. Bacterial contamination was effected by immersing in a Staphylococcus aureus suspension of 6 X 10(8)/ml for 15 minutes. The fragments were replaced and either left detached or fixed with a lag screw. In a number of cases bone replacement was combined with transverse osteotomy followed by reduction and fixation with a six-hole neutralization plate based on the AO-principle. Follow-up carried out after six and 12 weeks, comprised radiological, histological, microradiographic, fluorescence microscopic and micro-angiographic investigation. Non-quantitative assessment indicated that the rate of resorption and new bone formation in the bacterially contaminated fragments definitely exceeded that of the uncontaminated fragments. Semi-quantitative findings seemed to confirm these conclusions. After 12 weeks this difference had virtually disappeared, except in loosely replaced infected fragments, which still showed more resorption and new bone formation. Integration of all fragments was good, there was no encapsulation with sequestration.

Animals↗
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↗
PubMed1983

Cartilage tube formation by perichondrium: a new concept for tracheal reconstruction.

The formation of a cartilage tube by perichondrium around a silicone rod is described. Variables introduced in three experiments were (1) perichondrium of auricular elastic cartilage versus that of rib hyalin cartilage, (2) intramuscular versus subcutaneous insertion of the implants, and (3) the position of the chondrogenic layer of the perichondrium either facing the rod or facing outward. A stable and rigid cartilage tube with a smooth inner surface was obtained by using rib perichondrium preferably with the chondrogenic layer facing the rod. No differences between subcutaneous and intramuscular insertion of the transplants were noted.

Animals↗