Search PubMed⌕ Search

Biomedical subjects

K Donath

Publications and source records attributed to K Donath.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1991

[Clinical course, histology and prognostic assessment of odontomas].

In our opinion ameloblastic fibro-odontoma seems to be a true neoplasia. Complex composite odontomas and compound composite odontomas represent hamartomatous malformations. The ameloblastic fibro-odontoma seems not to differentiate into a complex composite odontoma. Since ameloblastic fibro-odontomas bear great resemblance to common odontomas, it is suggested that all odontomas be sent to a qualified oral pathologist for microscopic examination.

Adolescent↗
PubMed1991

[Ameloblastomas in the growth period--aspects of differential diagnosis and therapy].

This paper is focussed on problems associated with the histological evaluation of odontogenic tissues in the growth period. It is particularly parts of the dental lamina or harmless odontogenic tumors (e.g. ameloblastic fibromas) that can be mistaken for ameloblastomas. Since these false diagnoses may occur in growing patients, radical resections for treatment of ameloblastomas should only be performed after a second histological evaluation and when typical intraosseous lesions are present.

Adolescent↗
PubMed1991

[The in-vitro study of the marginal fit accuracy of computer-milled titanium crowns. II. A histological-morphometric marginal-gap analysis].

The Digitising Computer System (DCS) can be mechanically programmed to produce computer-milled titanium dentures for veneered ceramic single crowns using three-dimensional computer models. A first analysis by electron scanning microscope of the marginal leakage in titanium framework on 12 extracted teeth showed a marginal accuracy of fit of 68.3 +/- 61.1 microns for the shoulder, and 95.7 +/- 83.2 microns for the chamfered preparation. Owing to limited indicative value of recordings by electron scanning microscopes, the crown edges of the 9 teeth with shoulder preparations were subjected to histological-morphometric measurements. Using this more accurate investigational system, a distinctly higher arithmetic mean of 89.2 +/- 69.1 microns for the marginal accuracy of fit was achieved. It also enabled the marginal leakage of cement (96.5 +/- 85.1 microns), the marginal adaptation (37.4 +/- 93.3 microns) and the shoulder formation (44.4 +/- 58.9 microns) to be judged.

Computer Simulation↗
PubMed1990

[Developmental disorders of the permanent dentition following fractures of the visceral cranium during the growth period. Incidence and morphological findings].

The retrospective examination of 70 patients who had suffered fractures in tooth-bearing segments of the maxilla and the mandible when they were between one and twelve years old revealed a high incidence of late pathologic changes (in 39 out of 70). Disorders in odontogeny, eruption of the teeth and occlusion were observed. Primary and secondary loss of teeth did also occur. Our results show the necessity to inform both the young patients and their parents about the high incidence of late changes after jaw fractures in childhood. An effective recall-system is required in order to diagnose and treat such changes as soon as possible.

Child↗
PubMed1990

[Development and significance of the cuticula dentis for the epithelial attachment].

The purpose of this study was to identify those conditions governing presence and function of the secondary cuticle (cuticula dentis) by means of a clinical evaluation (Periodontal Status, Plaque Index, Decayed-Missing-Filled-Index) as well as radiological, bacteriological (plaque swabs) and histological studies. The secondary cuticle could be demonstrated mainly in individuals with mild bone resorption and minimal loss of periodontal attachment (age 20-50 years). In most cases there was an intimate attachment of the junctional epithelium to the enamel or cementum surface. However, in most elderly subjects (older than 50 years) the secondary cuticle was found only in fragments or was not detectable at all. In these cases the junctional epithelium had proliferated apically (towards the apex dentis) and was only punctiformly attached to the tooth surface. Our histological findings suggested that the secondary cuticle is a secretory product of the junctional epithelium. Therefore, we assume it to be the essential structure in maintaining epithelial attachment.

Adolescent↗
PubMed1990

[Development of plaque-induced gingival pockets in an animal experiment].

Single teeth and resected jaw specimens including periodontal tissue were prepared as saw-cut thin-ground specimens without previous decalcification. The specimens were classified into 4 stages of pathogenesis to allow studies into the mechanisms of gingival pocket formation. Examination of the preparations under the light microscope indicated that the pathologic gingival pockets caused by microbial plaque might be formed by degenerative alterations in the second or third innermost cell layer of the junctional epithelium. The intercellular contacts were dissolved and, thus, cyst-like cavities were formed within the epithelium. The contact between tooth enamel/cementum--basal membrane--epithelial cells, however, was maintained. Artifacts could be ruled out by comparing preparations of single teeth with those of entire jaw segments.

Animals↗
PubMed1989

Digital flashing tomosynthesis (DFTS)--a technique for three-dimensional coronary angiography.

Digital Flashing Tomosynthesis (DFTS) represents a technique for three-dimensional (3D) coronary angiography. Four ECG-gated simultaneously flashed X-ray tubes generate a multiperspective digital substraction image as DFTS multiangiogram for 3D reconstruction and visualization. Computerized morphologic and morphometric quantitative analysis can be performed including videodensitometry. Postmortem coronary angiography of 30 human hearts with suspected coronary artery disease was performed by 35-mm cine technique and by DFTS. The results of angiographic measurements in 50 stenotic arterial segments were compared with the histologic reference and show excellent regression results with correlation coefficients of more than 0.95 (p less than or equal to 0.0001). No significant differences in standard errors of estimates between the techniques were found. DFTS yields an accuracy in depiction of the coronary arteries and angiographic estimation of arterial lumen equivalent to 35-mm cineangiography. DFTS images can be directly used for visual interpretation and for computerized morphologic and morphometric quantitative analysis. DFTS technology reduces the amount of radiation exposure, the amount of contrast medium, and the time of the procedure. DFTS offers the possibility to obtain 3D images of the coronary artery tree.

Aged↗
PubMed1989

[Periodontal reactions to orthodontic forces in the diabetic metabolic state].

The reaction of the periodontium to orthodontic tooth movement was studied in rats with streptozotocin diabetes. Forces employed to initiate mesial movement of first molar were 10 N 20 N 30 N and the duration of application was three, six, ten and 14 days. The 14-day rats were treated with fluorochrome sequential labelling according to Rahn. Diabetes mellitus in rats is accompanied by characteristic changes: The most important findings were: 1. a slow osseous regeneration, as could be shown by fluorescence microscopy, 2. the new bone ist unable to pick up the labellings in a sequential manner, 3. a weakening of the periodontal ligamentum, 4. microangiopathies in the gingiva area. the specific diabetic changes are more pronounced following orthodontic tooth movement.

Animals↗
PubMed1989

[Periodontal reaction to orthodontic measures].

In twelve rats, the right maxillary first molar was moved mesially by means of a fixed appliance. It was not possible to find any histopathological differences with forces of 10 N, 20 N and 30 N. We also found no different cellular reactions in the tension and pressure zones between the periods of three, six, ten and 14 days. In the treated rats the first molar was tilted. The mesial root was intruded. Local pressure zones were regularly formed around the mesial root and distal aspect of the alveolar crest of the bifurcation. It could be shown by vital polyfluorochrome staining that there was no mesial tooth movement; rather distal drifting was delayed.

Adult↗
PubMed1989

Interface between bone tissue and implants of solid hydroxyapatite or hydroxyapatite-coated titanium implants.

Loaded prestressed implants of dense hydroxyapatite and non-loaded hydroxyapatite-coated titanium implants were placed in edentulous regions of the lower jaw of dogs. After 6 month the jaw specimens were fixed and embedded in methyl-methacrylate. Thin non-decalcified ground sections were made for histology. Although the hydroxyapatite showed histological differences between the coated implants and the prestressed solid ones, both had an extensive apposition of normal lamellar bone on the whole surface of the bone-buried part of the implant. The bone contact was very intimate and without any visible intermediate tissue layer. The tissue response observed forms a good biological base for the clinical application of hydroxyapatite-coated titanium implants.

Animals↗
PubMed1989

[Initial experiences with the dentin-ossicle prosthesis].

The results of 73 implantations performed from 1.7.1986-30.6.1988 are reported in a first follow-up study. 82% reached an air-bone gap of less than 30 dB, 55% of less than 20 dB. In comparison with other materials recently reported the functional results are a little less favourable due to the high percentage of revision surgery in our patients. Only few complications had to be noticed: no single extrusion was observed, but in one case a nearly complete resorption of the DOP was seen. Two DOPs, removed by revision surgery, were examined histologically. Beside resorptive processes, bony changes as a sign of biointegration into the middle ear were found. On account of our first results, DOP seems very suitable for the reconstruction of a destroyed ossicular chain, especially in cases where the autologous ossicles are not available.

Adolescent↗
PubMed1989

[Extra-osseous maxillary cysts--nasolabial cyst].

The maxillary cysts are classified on the basis of the recommendations by the World Health Organisation (1971), based on pathogenic criteria, in developmental and inflammatory, odontogenic and nonodontogenic cysts. Only two maxillary cysts lie primarily extraosseous: a non-odontogenic cyst, the nasolabial cyst, and an odontogenic cyst, the gingival cyst. The nasolabial cyst is a rare, developmental, non-odontogenic maxillary cyst, which offers the peculiarity of its constant extraosseous localization. On the basis of our cases from 1966 to 1988 the clinical patterns, histopathology, differential diagnosis, therapy, prognosis and histopathogenesis of the nasolabial cyst are presented.

Adolescent↗
PubMed1989

Impact of compensatory enlargement of atherosclerotic coronary arteries on angiographic assessment of coronary artery disease.

To determine whether compensatory enlargement of atherosclerotic coronary arteries occurs and to what degree it affects the angiographic assessment of coronary artery disease, we performed postmortem coronary angiography of 30 human hearts with suspected coronary artery disease and studied 70 histologic cross sections of the proximal left anterior descending artery and proximal right coronary artery. Angiographic and morphometric analyses of 50 stenoses in proximal and middle sections of the left anterior descending artery, right coronary artery, and left circumflex artery were performed. The control group of 10 human hearts without suspected coronary artery disease was evaluated in the same way. For this purpose, coronary arteries were filled with a methylmethacrylic radiopaque resin at a pressure of 100 mm Hg and closely embedded in a methylmethacrylic resin by use of which shrinkage and mechanical artifacts could be avoided. The area circumscribed by the internal elastic lamina was taken as a measure of the area of the arterial lumen if no plaque had been present. The angiographic and corresponding morphometric degree of stenosis was assessed. A significant correlation (r = 0.85, p less than or equal to 0.0001) was found between the internal elastic lamina area and the area of the plaque (lesion area), suggesting that coronary arteries may enlarge as lesion area increases. With the morphometric degree of stenosis, the expected anatomic diminution of the coronary artery was abolished (r = 0.79, p less than or equal to 0.0001), indicating compensatory enlargement in atherosclerotic segments. Accordingly, the degree of stenosis assessed from in vitro angiograms was underestimated. Compensatory coronary enlargement of the stenotic segment was the main reason for angiographic underestimation. The underestimation factor of up to 3.50 for very mild stenoses decreased to 1.37 at an angiographic degree of 50% area stenosis and 30% diameter stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

[Alveolar bone density under crowns, bridges and natural teeth without artificial crowns].

In an attempt to settle the moot question if alveolar bone density decreases under dental bridges, we determined bone density (bone volume, BV) in 60 interdental spaces of 30 mandibular or maxillary segments by histology and morphometry. Moreover we measured the thickness of the cribriform lamina. Our investigations included segments with healthy teeth and ones with splinted teeth, crowns or three-unit dental bridges. The results actually confirmed a decrease in bone volume under bridges compared to normal teeth in maxillary samples, whereas no differences in bone volume could be found in the mandibular samples. We could not demonstrate any correlations to age or sex up to 48 years.

Adolescent↗