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Biomedical subjects

K Donath

Publications and source records attributed to K Donath.

At least 19 recordsLinked to original sources
PubMed1992

The histopathology of different foreign-body reactions in oral soft tissue and bone tissue.

Foreign bodies may be endogenous or exogenous and provoke chronic inflammation of the foreign-body type. The reaction provides a mechanism for elimination of the foreign body and the reaction pattern depends on the kind of tissue involved. In soft tissues there is cellular inflammation and fibrous encapsulation with macrophages. In bone, during the healing period, biomechanical factors determine whether a fibrous encapsulation or a bony covering develops demarcating the foreign material. The particular characteristics of the foreign-body reaction in bone explain the success of dental and orthopaedic implants.

Animals↗
PubMed1992

[Histological studies of the behavior of the dentin ossicular prosthesis in the human middle ear].

The Dentine Ossicular Prosthesis (DOP)--introduced in the ENT-Department, University of Hamburg in 1986--has proved its worth clinically in more than 300 cases. In the meantime six of the prostheses had to be removed for various reasons. They had remained in the middle ear over a period between 2-5 and 47 months. The prostheses were investigated undecalcified by the Donath sawing and grinding technique. Prostheses in a nearly bland surrounding show a partial invagination in fibrous connective tissue without severe reaction of the prosthesis itself, whereas in prostheses removed from the neighbourhood of inflammatory processes or recurrent cholesteatoma a partial resorption of dentine with subsequent new bone formation could be observed. Due to the trouble-free clinical and histological performance in the human middle ear, the Dentine Ossicular Prosthesis can be well recommended as an alternative material in ossiculoplasty.

Adolescent↗
PubMed1992

Alveolar ridge augmentation by osteoinductive materials in goats.

The purpose of the present study was to determine whether alveolar ridge augmentation could be induced in goats. In 12 male goats allogenic, demineralized, and lyophilized dentin or bone was implanted subperiosteally on the buccal sides of the natural edentulous regions of the alveolar process of the mandible. Light microscopic evaluation revealed fibrous encapsulation, a few multinuclear giant cells, little inflammatory reaction, and no osteoinduction. It was concluded that no osteoinduction took place in goats.

Alveolar Ridge Augmentation↗
PubMed1992

Light and transmission electron microscopy of the intact interfaces between non-submerged titanium-coated epoxy resin implants and bone or gingiva.

This experiment was aimed at studying the intact tissue/implant interface of non-submerged dental implants with a titanium surface. Epoxy-resin replicas were fabricated from 3.05 x 8 mm cylindrical titanium implants with a plasma-sprayed apical portion and a smooth coronal collar. The replicas were coated with a 90-120-nm-thick layer of pure titanium and autoclaved. The coated replicas were inserted as non-submerged endosseous implants in the edentulous premolar region of dog mandibles and allowed to heal for three months. Jaw sections containing the implants were processed for light and electron microscopic study of the intact tissue/implant interface with and without prior demineralization. Gingival connective tissue fibers were closely adapted to the titanium layer, in an orientation more or less parallel to the implant surface. There was no evidence of any fiber insertions into the surface irregularities of the smooth or rough titanium surface. Undemineralized bone was intimately adapted to the titanium surface without any intervening space. In demineralized sections, the collagen fibers of the bone matrix tended to be somewhat thinner and occasionally less densely packed in the vicinity of the implant surface. However, they extended all the way to the titanium surface, without any intervening fibril-free layer.

Alveolar Process↗
PubMed1992

A comparison of ePTFE membranes alone or in combination with platelet-derived growth factors and insulin-like growth factor-I or demineralized freeze-dried bone in promoting bone formation around immediate extraction socket implants.

The purpose of this study was to compare bone promotion around implants which were augmented with ePTFE membranes alone or in combination with cortical demineralized freeze-dried bone (DFDB) or the combination of platelet derived growth factor-BB (PDGF) and insulin like growth factor I (PDGF/IGF-I). Membranes were placed over titanium implants which had been inserted into fresh extraction sockets with large buccal dehiscences. Twenty-four implants were placed in 4 dogs. At 18 weeks clinical bone height measurements were taken, the animals were sacrificed, and all specimens retrieved for histologic evaluation. Clinically, a significant gain in bone levels was present in both the ePTFE membrane alone group (P < 0.005) and PTFE plus PDGF/IGF-I group (P < 0.01), but not in the PTFE plus DFDB group. Results from histometric measurements revealed an approximately 2-fold increase in the percentage of implant surface in contact with bone, area of bone adjacent to the implant surface, and in the total length of the implant surface in contact with bone in the dehiscence defects treated with ePTFE plus PDGF/IGF-I compared to the defects receiving ePTFE membranes alone (each P < 0.05). The response to the DFDB was highly variable and it did not significantly improve the efficacy of the PTFE membranes for any parameter measured. The distance from the outer surface of the new bone to the implant surface was statistically significant for ePTFE membranes alone and membranes plus PDGF/IGF-I. The results demonstrated that clinically, ePTFE membranes alone or ePTFE membranes with PDGF/IGF-I were equally effective in promoting bone growth around the implants. Histologic measurements demonstrated that sites treated with ePTFE membranes plus PDGF/IGF-I had the highest bone density compared with sites which received ePTFE membranes alone or with ePTFE membranes and DFDB. The results of this study question the use of DFDB and support the use of ePTFE membranes alone or with PDG-F-BB/IGF-I as potential methods of promoting bone formation around dental implants.

Alveolar Bone Loss↗
PubMed1992

Soft tissue reactions to non-submerged unloaded titanium implants in beagle dogs.

The soft tissue reactions to non-submerged unloaded titanium implants were examined. A total of 24 implants were placed in 6 beagle dogs. The implants differed in their crestal area by having either a rough sandblasted, a fine sandblasted, or a polished surface. After 3 months, all implants were firmly anchored in the bone and had no clinical signs of peri-implant inflammation. Undecalcified histologic sections demonstrated that all implants achieved osseointegration with direct bone contact. The epithelial structures showed a peri-implant sulcus with a non-keratinized sulcular epithelium and a junctional epithelium. None of the sections exhibited epithelial downgrowth to the alveolar crest. In the supracrestal area, a direct connective tissue contact to the implant post was observed. An approximately 50 to 100 microns wide zone of dense circular fibers was found close to the implant surface. It was free of blood vessels and resembled closely an inflammation-free scar tissue formation. This zone was surrounded by a looser connective tissue with a 3-dimensional network of collagen fibers running in different directions. No significant differences concerning soft tissue reactions were found between the 3 implant surfaces. In particular, the length of direct connective tissue contact was similar. Concerning bone reactions, a significantly shorter distance from the top of the implant to the most coronal bone-implant contact was observed for rough surfaces. It is concluded that non-submerged unloaded titanium implants achieved a complication-free tissue integration with a dense connective tissue in direct contact to the implant surface in the supracrestal area, and epithelial structures similar to those around natural teeth. The different surface textures did not influence the healing pattern of the soft tissues, but had an influence on the location of the most coronal bone-implant contact.

Alveolar Process↗
PubMed1992

[Cysts and tumors of the jaw bone].

The new entities of cysts and odontogenic tumors of the second edition of WHO "Histological Typing of Odontogenic Tumors" (Kramer et al., 1992) are presented. The classification is based on tumor behavior. The benign epithelial odontogenic tumors are classified in relation to tooth development. The malignant odontogenic tumors are subdivided in carcinomas, sarcomas and carcinosarcomas, which are very rare. This international classification has the purpose to make rare cases comparable, so that more detailed knowledge of their characteristics can be achieved. Types of bone tumor that also occur in other parts of the skeleton are not discussed here.

Bone Diseases↗
PubMed1992

Retrieval analyses of a blade implant after 231 months of clinical function.

A blade implant that was retrieved in 1990 after 231 months of clinical function (since 1971) was analyzed with respect to clinical, histological, and biomechanical characteristics. The implant clinical records demonstrated no abnormalities or pathological lesions over the tenure of treatment. The bone to implant interface showed a mixture of interfacial tissue components and conditions with adequate direct bone contact (46.4 to 82.3 percent) for classification as osseointegrated. The abutment fracture leading to removal was characterized as a cyclic fatigue mechanism and the distribution of tissue components along the interface could not be correlated with specific biomechanical loading directions. This report considers the clinical and biomechanical records as they relate to the detailed histological investigation.

Blade Implantation↗
PubMed1992

[Diagnosis and differential diagnosis of squamous epithelial metaplasia in the parotid gland].

The authors report a case of proliferating squamous epithelium in the necrotic edge of multifocal oncocytic adenomatous hyperplasia of the parotid gland. A correct histological diagnosis is of great clinical relevance and difficulty, since similar findings can occur in mucoepidermoid carcinoma. The various cell types in the parotid gland and their roles in neoplasia are discussed.

Adenoma↗
PubMed1992

Pathogenesis of bony pocket formation around dental implants.

This study was undertaken to explain differences in the pathogenesis of periodontitis and peri-implantitis. Histological observations were made on experimental and human material obtained at autopsy. The sections were prepared without decalcification and without removal of the implants by the cutting and grinding technique. In some cases the implant was exposed but the mucosa surrounding it showed no inflammation. In other cases granulation tissue had formed around the implants resulting in a polypoid mass and the adjacent mucosa was inflamed. A discussion and comparison of the pathogenesis of periodontitis and peri-implantitis is given.

Adult↗
PubMed1992

[Histological study of the resorbed dental crowns of impacted wisdom teeth].

Undecalcified sections of 31 impacted third molars are examined histologically for signs of resorption. Resorption starts at small spots in enamel, progresses to dentin and may even penetrate the pulp cavity. The incidence of such resorption processes increases after the age fifty. A prerequisite for resorption is the loss of reduced ameloblastic epithelium. Histological examination reveals multinuclear giant cells and apposition of spongious bone to destroyed dental substances. The results is dental ankylosis. Because partially resorbed teeth or ankylosed teeth may lead to serious surgical difficulties, impacted wisdom teeth without any clinical symptoms and without pathologic radiological findings should always be extracted at a young age.

Dental Enamel↗
PubMed1991

Intra-oral keratoacanthoma: an eruptive variant and review of the literature.

Intra-oral keratoacanthoma, occurring in the absence of cutaneous lesions, is a rare lesion which may resemble a well-differentiated squamous cell carcinoma both clinically and histologically. A case is reported of two simultaneously occurring keratoacanthomas, of the eruptive variant, on the hard palate of a 25-year-old woman. A review of the English literature, which has identified ten documented cases to date, is presented.

Adult↗
PubMed1991

Histologic findings of apatite-titanium complex dental implants in the jaws of dogs.

This study concerns the histologic examination of apatite-titanium complex dental implants (two-piece, cylindrical type) in dogs. There was no plaque control. One to 3 months after implantation, the surface of the apatite root was directly bound to newly formed, woven bone. Seven-and-a-half months to 1 year after implantation, the apatite root was directly bound to the newly formed lamellar bone, which provided strong bone bonding (apatite-bone bonding). There appear to be two types of mechanisms for the resorption of apatite ceramics: first, cellular-type resorption by both multinuclear and mononuclear macrophages; and second, a noncellular, fluid mechanism (dissolution). The gingival sulcus around implants and downward growth of the epithelial cells could be observed in almost all of the implants. There was no cellular inflammation in the tissue around the implants, in the nasal cavity, or in the maxillary sinus. From this study we concluded that clinical application of this dental implant system would be practical.

Animals↗
PubMed1991

[Complete airway obstruction by a prosthesis powder. The problem of protecting the airway in emergency service].

An extraordinary occurrence of death is reported due to blocking of the entrance of the larynx by a denture adhesive. The improper usage of this material by a mentally disturbed woman of 66 years of age caused her death by suffocation. In such a case an intubation can involve a transfer of the viscous material to the larynx. Therefore a coniotomy or a tracheotomy should be performed.

Adhesives↗
PubMed1991

Enzyme, lectin and immunohistochemistry of plastic embedded undecalcified bone and other hard tissues for light microscopic investigations.

Enzymes and tissue antigens were localized on plastic embedded undecalcified bones and teeth using Technovit 7200 VLC (Kulzer, Germany). This resin is hard enough for cutting and grinding procedures on rotating plates with diamond layers. The pores between the diamond grains are not obstructed with this resin. The procedure described here permits localization of antigens in the soft tissues adjacent to, or in the biological hard tissues themselves and in dental implants (ceramic or metallic) on the light microscopic level. The undecalcified bone is fixed and embedded in plastic and cut at 100-150 microns. The slices are ground automatically by a grinding machine to a thickness of 5-10 microns. After application of the substrates for alkaline and acid phosphatases and the required dyes, the distribution of these enzymes can be demonstrated. Tissue antigens also can be detected with slightly modified standard techniques of immunohistochemistry and lectin histochemistry using the peroxidase technique or fluorescence microscopy.

Ameloblasts↗
PubMed1991

[Treatment of keratocysts in deciduous and mixed dentitions].

A survey is given of patients with odontogenic keratocysts in childhood and adolescence which were treated at the Clinic for Maxillofacial Surgery Tübingen in the last 10 years. Odontogenic keratocysts occurring in the growth period are treated in most cases by enucleation or partial marsupialization. To avoid damaging the nerve or dental germs, fixation with Carnoy's solution is not performed. In a second part an experimental study dealing with the effects of Carnoy's solution on peripheral nerves is presented. After incubating the sciatic nerve of rats with Carnoy's solution lumbar SEP, M-response and Hoffmann's reflex were recorded. It was possible to demonstrate the detrimental effect of Carnoy's solution on peripheral nerves. After incubation periods of more than 2 minutes almost complete functional loss was observed. There was a strong correlation between electrophysiological and histological findings.

Acetates↗
PubMed1991

[Frequency of odontogenic tumors in the growth period].

424 odontogenic tumors were diagnosed at the Department of Oral Pathology in Hamburg Eppendorf and the Department of Maxillofacial Surgery in Kiel between 1965 and 1989. 106 of these odontogenic tumors were found in patients of 16 years and under. More often than not the odontogenic tumors of this age group were complex and compound odontomas, totalling 67%. When comparing these with other odontogenic tumors it must be taken into consideration that--although included in the WHO classification--odontomas are often referred to as hamartomas and not real tumors, because they lack the typical features of tumors. Compared with the adult age group, the relative frequency of ameloblastic fibromas, ameloblastic fibro-odontomas and odontogenic myxomas was remarkable. Nevertheless, because of the great differences between the two age groups, direct comparisons of these findings with each other should be made with reservation.

Adolescent↗