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Biomedical subjects

G Heimke

Publications and source records attributed to G Heimke.

At least 37 records · Page 2Linked to original sources
PubMed1980

Ceramic keratoprostheses.

This paper describes a new type of corneal prosthesis made of aluminum oxide ceramic. The implant consists of a retaining plate with a 3-mm central performation to which an optical cylinder is threaded. The cylinder also made of ceramic material, has a high refractive index and 60 diopters of power. Experimental study has shown that soft tissue adheres to the surface of the material, thus preventing its extrusion and surface epithelial ingrowth. The techniques of implantation and the early results in seven patients are described.

Adolescent↗
PubMed1979

Direct anchorage of Al2O3-ceramic hip components: three years of clinical experience and results of further animal studies.

The biocompatibility of high-purity dense Al2O3-ceramics had been shown to open the possibility of direct cement-free anchorage of joint endoprostheses. Three years of clinical experience with ceramic-metal composite total hip prostheses confirm the biomechanical design criteria used for the acetabular components. They also allow for additional conclusions regarding the reaction of bone tissue towards a bioinert implant. Further research activities are directed towards a solution for biomechanically stable anchorage of the femoral component of hip prostheses.

Aged↗
PubMed1978

[A new technique for socket implantation into dysplastic acetabula (author's transl)].

This report presents a new technique of socket implantation into the dysplastic acetabulum. A major part of the resected femoral head serves as the so-called intra acetabular femoral head graft and is screwed into the lateral part of the original acetabulum. By this technique it is possible to achieve a complete bony reconstruction of the dysplastic acetabulum into which a square shaped small ceramic socket can be easily implanted using few especially designed instruments. After the description of the operative technique this report presents the clinical results of this procedure based on 11 personal cases. Finally the technical, biomechanical and biological advantages of this implantation technique are discussed in view of other similar methods described recently.

Acetabulum↗
PubMed1978

[Comparative experimental investigations with bioglass (L. L. Hench) and Al2O3-ceramic coated with mod. bioglass. II. Results of experiments with loaded implants (author's transl)].

This report is based on 4 comparative experimental series is sheep using a cementfree total hip replacement model. Basically a smooth stem design was compared to a step stem design for biomechanical interlocking anchorage. Both designs were implanted as pure high density Al2O3-ceramic components and as Al2O3-ceramic parts coated with Bioglass or Bioglass-ceramic (post op. follow up 13 months, 17 animals). None of the 4 stem modifications showed a tendency for permanent stabilisation or bonding in bone. Besides insufficient bonding of the glass coatings to the substrate and apparent biodegradability of the bioglass coatings in the body, insufficient biomechanical knowledge of endosteal direct anchorage of prosthetic devices is the main reason for failure in these experiments. An exclusive biochemical way of anchoring prosthetic parts in the marrow cavity is rejected. The results presented are discussed in the light of the recent literature.

Aluminum Oxide↗
PubMed1978

[The relevance of histological results for the evaluation of materials for bone replacement (author's transl)].

Different groups have observed and reported deviating tissue reactions for the same material for bone replacement: for the "bioinert" Al2O3-ceramic close bone contact is mentioned, others report about a soft tissue layer adjacent to the implant; for the "bioactive" glass ceramic interfaces capable to transmit considerable shear forces are described, others found no interface bonding.--The analysis of the results of animal experiments and the evaluation of clinical follow-up studies show that these discrepancies had been caused by the differences of the biomechanical situations in the examined interfaces. It is pointed out that the negligence or not mentioning of the load pattern at the site of examination can lead to misinterpretations about the possibilities and limits of applicability of biomaterials.

Aluminum Oxide↗
PubMed1978

[Endosseous aluminum oxide-ceramics implantations. The activities of a work group sponsored by the county government of Baden-Württemberg].

Emanating from the recognition of the favourable body tolerance of some ceramic substances in the U.S.A., investigations were started in 1970 with a view to the possibilities to improve endoprosthesis of joints by the use of Al2O3 ceramics. The experience collected brought a new insight into bio-mechanically based reactions occurring in osseous tissue bordering the implant. Their use in tooth implants led to corresponding adaptations of implant forms.

Aluminum Oxide↗
PubMed1978

[The effect of the shape of aluminum oxide-ceramic implants on its staying power in the dog mandible].

Investigations were carried out on implants of Al2O3 ceramic as secondary single toothe replacement in the lower jaw of young Beagle test dogs. Two basically different forms with altogether 7 variations were tested: the first three types of implants had conical roots and a further 4 had cylindrical roots. Common to all 7 types was an implantation shoulder which was tested for its ability to conduct the masticatory force via the cortical substance to the mandibular bone. All implants are at least under indirect masticatory strain; type 80-40-027-00 was directly under strain: part of the implant, shaped like a premolar protrudes through the gum directly into the oral cavity. Preliminary results show that cylindrical root shapes stood the test well. Their length was of no great importance. Conical root shapes without special provision of retention are not suitable. Firm positioning of the implant during introduction is of prime importance. A cortically placed implantation shoulder is not suitable for the conduction of the masticatory pressure into the mandibular bone in dogs.

Aluminum Oxide↗
PubMed1978

[Animal experiments on the question of healing around the Tübingen immediate implant].

In order to determine the capacity for deposition of bone, 5 Beagles were each implanted extraorally with 6 aluminium oxide cylinders into the horizontal mandibular ramus. 4 months after the first implantation a second implantation was carried out in the opposite side with similar cylinders. After six months all were removed so that in altogether 60 implants the bone deposition could be observed 4 months and 2 months after implantation. A further 14 dogs received altogether 55 Tuebinger immediate implants. All animals were regularly observed post-operatively. After 6 months all cylinder full-implants had been accepted without reaction. All tooth implants which were either not put under strain or were immediately put under pressure healed without reaction. After three months 19 implants were lost and a further 5 were lost after 8 months. All cylinder implants were histologically examined 6 months after first implantation.

Animals↗
PubMed1978

[Light and scanning electronmicroscopic studies of border surfaces of aluminum oxide-ceramic implants in the dog mandible].

The mandibular bone of beagles as well as foxhounds and the border surfaces in the area of implants of dense Al2O3 ceramic were examined by scan electron microscope and optically in undecalcified preparations 4 and 6 months after the start of the experiment. All implants healed without foreign body or inflammatory reaction and exhibited a firm contact with the newly-formed surrounding osseous tissue. The border surface was always formed by osseous tissue and bone marrow and not by connective tissue. The bony border surface presented a casting of the structure proper of the ceramics as well as orderly remodelling. The tooth implants which had in part been under strain for a long time were surrounded by newly formed osteoid bone and supported by bone trabeculi. In the immediate proximity of the surface of the ceramic vital osteophites were found. The gum which was placed in a groove of the step implants showed firm epithelial covering and orderly fibrous texture.

Aluminum Oxide↗
PubMed1978

[Concept and testing of the Tübingen immediate implant].

This introductory communication deals with the functional-anatomical, biophysical and neurophysiological considerations which led to the construction of an aluminium oxide immediate implant from a stepped cylindrical body. This intra-osseous implant differs in essential constructional features from the implant shapes known up to now; it endeavours to make use of the architecture of the natural gingival fibre apparatus for the placing of the mucosal cuff. Its surface was maximalised towards the bone, leaving out surface structures which could produce pressure points. The enlargement of surface compared with the root of the corresponding natural tooth amounts to 65 to 100% varying according to the shape of the implant. Descriptions are given of the concept of testing experimental implants, the physical and chemical characterisation of surfaces, animal-experimental steps, clinical tests including legal problems posed and the control system created with the view to large scale clinical trials.

Aluminum Oxide↗
PubMed1977

[Comparative experimental investigations with bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. Bioglass. I. Results of experiments under non-loaded conditions (author's transl)].

This report deals with comparative results obtained with unloaded intra-osseous implants of bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. bioglass. Al2O3-ceramic and bone form a direct bony interface without fibrous tissue interposition, this resulting in a pure mechanic fixation of the implant through frictional forces of the surface roughed ceramic. Pure bioglass (45S5) and bone form a unique persisting direct interface by means of physico-chemical or biochemical phaenomena stabilizing the implant. Interface stability seams to be higher than the fatique strenth of the glass itself. This interface is developed as a consequence of solubility of some of the glass constituents within a surface layer of up to 200 microns, running parallel with a reduction of strength of this surface glass layer. The boronoxide containing bioglass, flame-sprayed onto Al2O3-ceramic samples seams to be less soluble and therefore seams to have lesser bonding capability to bone. The stability of the interface bioglass coating-Al2O3-ceramic was low.

Aluminum↗
PubMed1977

[Experimental investigation on non-specific foreign body sarcoma induction of Al2O3-ceramic implants (author's transl)].

This investigation presents experimental results on possible non-specific foreign body sarcoma induction by Al2O3-ceramic implants. Solid and porous discs, subcutaneously implanted in rats produce a sarcoma rate of 17.4 resp. 17.8 p.c. while roughly perforated discs initiate sarcomas at a rate of 25.4 p.c. These values were found to be lower than comparative values in the literature produced with different metals and medical grade plastics. Powdered alumina implants did not produce any sarcomas. Only this latter result can mainly be transferred into prognostic assumptions concerning the clinical application of Al2O3-ceramic. The results are discussed extensively in the lights of the existing literature, this indicating that the tested ceramic itself may not possess a significant sarcogenetic potency in humans.

Aluminum↗
PubMed1976

Evaluation of a bioglass-coated Al2O3 total hip prosthesis in sheep.

A bioglass-coated fully dense alumina total hip was evaluated in sheep without using polymer bone "cement." After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone-implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.

Acetabulum↗
PubMed1976

Biomechanically induced tissue reactions after Al2O3-ceramic hip joint replacement. Experimental and early clinical results.

A biomechanical concept of interface maturation around cement-free implanted alumina-ceramic hip endoprostheses in sheep is explained. Provided there is rigid primary stability of the implant within the bone bed, hard tissue formation along the support areas of the implant is mainly dependent on implant shape and main local stress direction. Three subsequent phases of interface maturation can be distinguished, finally resulting in firm fixation of the implant by mechanical interlocking of supporting bone and ceramic. A new composite alumina-metal hip endoprosthesis for partial cement-free implantation (cup) is presented. The technique, postoperative care, and encouraging early results in 5 patients are demonstrated. A new ceramic femoral component for cement free implantation is proposed.

Acetabulum↗