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Biomedical subjects

K Donath

Publications and source records attributed to K Donath.

At least 127 records · Page 7Linked to original sources
PubMed1988

The mechanism of pocket formation. A light microscopic study on undecalcified human material.

Two hundred eighteen human teeth with surrounding periodontal tissues in different stages of pathogenesis were studied under light microscopy using the "sawing and grinding" technique. This was done without decalcification and with special emphasis on the dentogingival junction area so as to study the mechanism of pocket formation. Thirty early, 133 established, and 214 advanced lesions were included. No initial lesion was seen. Pocket formation, provoked by microbacterial plaque, seemed to be initiated by the degenerative changes in the second or third cell layers from the innermost cells in the most coronal part of the junctional epithelium facing the microbial plaque. Consequently, an intraepithelial cleavage was formed followed by the degeneration and desquamation of the cells lining the split. This resulted in a deep crevice and gingival pocket formation in both early and established lesions. In advanced lesions, the deep pocket epithelium was exposed for such a long distance adjacent to the plaque and calculus, that the epithelium could be directly affected by toxic bacterial products and mechanical irritation of calculus. Finally, the epithelium became very thin and ulcerated, and a typical periodontal pocket was formed. The disruption of the epithelial barrier along with the concomitant penetration of bacteria and/or their toxic products were considered to be the most significant factors related to the conversion of an established lesion to an aggressive lesion.

Epithelial Attachment↗
PubMed1987

A histologic evaluation of a mandibular cross section one year after augmentation with hydroxyapatite particles.

A pathologic mandibular fracture in a 35-year-old woman 1 year after the attempted filling of a bone defect with particulate, dense hydroxyapatite resulted in a partial mandibular resection, allowing observation of cross sections of the mandible and associated soft tissue. Thin tissue sections were examined without decalcification. This permitted excellent observation of the hydroxyapatite particles, the bone, and the soft tissue. Osseointegration had occurred only in the areas closely associated with the bone. The immobility of the particles was a prerequisite for involvement with new bone formation. Hydroxyapatite particles in areas that allowed any mobility were surrounded by connective tissue with no bone formation evident. Heterogeneous particles were observed, indicating the possibility of a lack of purity in the hydroxyapatite ceramic, which may have contributed to the resorption of the particles. These findings, as well as other clinical and experimental findings, lead us to question the concept of hydroxyapatite as a bioactive ceramic that induces osteogenesis or osteoconductivity.

Adult↗
PubMed1987

Is hydroxyapatite ceramic an adequate biomaterial in ossicular chain reconstruction?

The suitability of high-density hydroxyapatite ceramic without macropores for ossicular chain reconstruction was examined in animal experiments. The material was implanted both mobilely and immobilely, in compact cylinders and as granules at different locations. Biocompatibility was studied by the sawing and grinding technique without decalcification. If high-density hydroxyapatite was not in direct and stable contact with living bone, resorption and osteoneogenesis could not be observed. In cases of mobile contact with living bone there was a jointlike connection. Osteoneogenesis was seen only if the hydroxyapatite was in primary stable contact with living bone. We concluded that high-density hydroxyapatite ceramic, positioned as an ossicular replacement prosthesis, is an adequate biomaterial in ossicular chain reconstruction.

Animals↗
PubMed1987

[Preparation of hip joint endoprostheses for qualitative and quantitative morphologic assessment].

The morphological investigation of endoprostheses and the evaluation of the reaction with the surrounding bone tissue require the use of new preparation techniques. A standardized procedure of preparation is suggested to enable a comparison among various study groups. After removing the specimens (at autopsy), x-rays are taken, followed by separation into horizontal and longitudinal sections. These sections are undecalcified embedded retaining the implant/bone interface and grounded to thickness of 5-10 mu. First results of a quantitative analysis of bone loss are presented.

Bone Resorption↗
PubMed1986

[Mechanisms of tumor invasion in the laryngeal structure. A study of undecalcified thin sections].

Mechanisms of invasion of squamous cell carcinoma into the framework of the larynx were studied in nondecalcified acrylic embedded tissue. Destruction was always an indirect process mediated by giant cells or proteases. Two different stages of tissue specific response were seen. Bone was reacting with osteoneogenesis in the interface and with apposition of bone at the tumour non-attached side. Hyaline cartilage was responding with new formation of bone distant to the tumour and with production of protease inhibiting cartilage substance, whenever the tumour was attached to cartilage directly. Macrophages resorbed the product of these local tumour-host-interactions. There were plasma cells indicating a local immunological activity. In cases of irradiated carcinomatous larynxes this local immunological process seemed to be not in action. Here tumour invaded the skeleton of the larynx directly and microphages were seen removing the waste of destruction showing sequesters of cartilage and bone. These findings confirm the therapeutic principle that in carcinomas infiltrating the framework of the larynx irradiation is insufficient. Irradiation disarranges the specific local mechanism of defence and advances destruction and metastases by the tumour. Therefore, if operative treatment is not possible, it must be discussed, whether an alternative palliative proceeding--for example endolaryngeal reduction of tumour masses by laser surgery conservating the laryngeal framework--is a more adequate solution.

Aged↗
PubMed1985

Biology of metastasizing ameloblastoma.

The present report of a malignant metastasizing ameloblastoma and a critical review of literature was undertaken in an attempt to better understand the biological potential and behavior of this rare tumor and thus to facilitate its clinical management. Most of the 26 patients with a proven malignant ameloblastoma including the present case had developed multiple recurrences. The lung was the most frequent metastatic site (88%) followed by regional lymph nodes (27%). Furthermore metastases were observed in some cases in the bone, brain, kidney, small intestine and liver. The interval between diagnosis of tumor and manifestation of metastases was long with a median of 11.1 years. The average survival time was 13.1 years. By contrast, the interval between diagnosis of metastatic disease and death was relatively short (median: 2.6 years). The histologic and cytologic pattern of malignant ameloblastoma and of its metastases was not significantly different from that of non-metastatic ameloblastoma. Because of the lack of morphological criteria of malignancy the biological behavior of ameloblastomas cannot be predicted. It is difficult to be certain which factors are important in the delayed induction of metastases. It is suspected that ameloblastomas possess an inherent low grade malignancy which is stimulated by multiple recurrences. It is further assumed that the metastatic tumor cells have a slow growth rate resulting in late clinical manifestation of metastases. When lung metastases occur we recommend their surgical removal in order to prolong live expectancy or even to obtain a curative effect.

Adult↗