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Biomedical subjects

K Donath

Publications and source records attributed to K Donath.

At least 73 records · Page 4Linked to original sources
PubMed1995

Response of odontoblast-like cells to hydroxyapatite ceramic granules.

In this study the inductive influence of hydroxyapatite ceramic (HAC) granules on preodontoblast differentiation was investigated. Dental papilla cells harvested from upper molar tooth germs were implanted intramuscularly in a pouch created for this purpose. Six months after surgery tooth-root-like bodies had developed with pulp-like cavities in the specimens in which dental papilla cells had been implanted with and without HAC. These bodies consisted of regular tubular dentine in the central part, fibrodentine peripherally and sometimes osteodentine. HAC was haphazardly enclosed in these root-like bodies, whereas the implantation of HAC alone had no effect.

Animals↗
PubMed1995

Effect of age and radiation on bone healing adjacent to hydroxyapatite placed in the tibia of rats.

This study investigated the effect of age and radiation on healing after implantation of hydroxyapatite granule in bone. Two groups of 16 male Wistar rats, aged 4 weeks and 2 years were used for this study. Hydroxyapatite particles were placed into the tibia 28 days after the delivery of 15 Gy of irradiation from a Linac source. The results of the present study suggest that an old rat was more vulnerable to the radiation than a young rat. It seemed that age might also be an important factor in the prognosis of the implanted hydroxyapatite in irradiated bone.

Age Factors↗
PubMed1995

Experimental and clinical study on the vitality of orthotopic cartilage transplants.

Orthotopic cartilage transplants are performed in the course of numerous rhinosurgical operations. Precondition of a permanent success of the operation is preservation of vitality of the transplanted cartilage. Although numerous study results of heterotopic cartilage transplants exist, corresponding examinations in orthotopic transplants have not been done so far. Therefore, in 33 rabbits we did a partial submucous septumresection and put the cartilage back between the mucosal wall. After 1, 2, 3, 6, and 12 weeks, the animals were killed and the cartilage histologically proved. These results were compared to analogous human biopsies. Cartilage reintegration showed a characteristic picture. In the rabbit, the replanted cartilage was healed and stable after 3 months in each case. During reintegration, appositional growth started from the inner perichondrium. With microangiographical examinations, we were able to demonstrate that the speed of reintegration increased with decreasing distance of the cartilage cell from the blood vessels. We managed to confirm the experimental results in human cartilage biopsies.

Animals↗
PubMed1995

Histologic evaluation of osseointegrated implants restored in nonaxial functional occlusion with preangled abutments.

Of concern with the use of preangled abutments on implants is the transmission of masticatory forces and the angle at which they occur. Nineteen endosseous implants were placed in two subhuman primates. After 6 months, to allow for osseointegration, the implants were fitted with preangled abutments of various degrees and restored with type IV alloy castings. Straight abutments were used as control. Histologic evaluation revealed that, after 1 year of service, the implants exhibited complete osseointegration. Implants, whether restored with straight or preangled abutments, had no adverse effect on the surrounding bone. Soft tissue pockets measured, on average, from 2.2 to 2.6 mm; acute and chronic inflammatory cells were present. When crown loss was observed, it was caused by mechanical failure of components, such as gold screws and the screws used to secure the preangled abutments to the implants. Preangled abutments appear to be a valuable adjunct in implant dentistry, although long-term studies are needed for confirmation.

Animals↗
PubMed1994

[Ectopic meningioma of the tonsil].

To our knowledge this is the first reported case of a primary extracranial meningioma located in the palatine tonsil. Immunohistochemical investigation of the tumour showed coexpression of vimentin and neuron-specific enolase (NSE). No staining was found with antibodies against cytokeratins KL1, 13/10, 8 and 18, epithelial membrane antigen EMA and melanoma protein (HMB-45). It seems justifiable to classify this tumour as an atypical meningioma because of the local increased mitotic activity.

Adult↗
PubMed1994

Cutaneous manifestation of sarcoidosis (Boeck) with severe osseous destruction of the midface. A case report.

A 16-year-old Caucasian girl presented with brownish red plaques and papules beneath the right eye, and a right side open bite. The cutaneous changes had occurred more than 13 years previously. Radiological evaluation of the chest demonstrated bilateral hilar lymphadenopathy. Kveim-Siltzbach test of the skin was positive. Histological examination of several biopsy specimens taken from skin, oral mucosa and anterior wall of the right paranasal sinus revealed the diagnosis of sarcoidosis (Boeck). Therefore steroid therapy was initiated and the patient was placed on 40 mg prednisone daily. Under this treatment the sarcoidosis manifestations improved generally, and the prednisone dose was subsequently reduced.

Adolescent↗
PubMed1994

Titanium implant insertion into dog alveolar ridges augmented by allogenic material.

The purpose of this investigation was to evaluate whether titanium endosseous implants would osseointegrate in dog alveolar ridges augmented by allogenic material. In 8 dogs en bloc resection, including 2 pre-molars, was performed bilaterally in the maxilla and the mandible. After a healing period of 6 weeks allogenic, demineralized and lyophilized dentin or bone was implanted subperiosteally. Titanium implants were installed 5.5 months later in some of the regions. Light and fluorescence microscopic evaluation revealed fibrous encapsulation of the implanted allogenic material, no osteoinduction and only minimal osteoconduction, few multinuclear giant cells and a sparse inflammatory reaction. The titanium implants healed mainly by fibrous encapsulation.

Alveolar Process↗
PubMed1994

[Site and epidemiology of mucoepidermoid carcinoma. Analysis of 327 cases].

The salivary gland registry of the University of Hamburg (1965-1992) comprises a total of 327 mucoepidermoid carcinomas (MEC). MEC occur between the age of 5 and 96 years, most frequently in the sixth and seventh decade of life. The average age lies below 50 years (48.9 years). There is a slight predisposition of females (56.3%). Nearly 60% of all MEC care localised in the major salivary glands. The parotid gland is the most frequent localisation (53.5%) followed by the palate (17.4%). MEC are less frequent in the submandibular and sublingual glands, such as the minor salivary glands of the oropharynx and the cavity of the mouth. 53.2% of all MEC's can be classified as highly differentiated, the remaining 46.8% as poorly differentiated. MEC's of the palate are predominantly highly differentiated (72.0%). Among the variants of MEC, cystic (25.4%), clear cell (11.0%) and oncocytic (0.6%) tumours can be observed. MEC's of the clear cell type tend to originate from minor salivary glands (69.5%). MEC of childhood and adolescence (8.6%) are preferably seen in the parotid gland (46.4%) and the palate (39.3%). Up to the 20th year of life, cystic tumours and tumours of the clear cell type are comparatively more frequent.

Adolescent↗
PubMed1994

[Histology of mucoepidermoid carcinoma. Analysis of 327 cases].

The mucoepidermoid carcinomas of the salivary glands (MEC) show histologically a wide spectrum of differentiation from solid epidermoid tumours to cystic mucous-filled tumours. Epidermoid cells, mucous cells and intermediate cells are the main cellular components. Besides clear cell (11.0%) and oncocytic (0.6%) variants and "cystic" (25.4%) tumours can be observed. According to the per cent of mucous cells and cystic spaces of the total tumour mass different degrees of histomorphologic differentiation can be distinguished. Therefore highly differentiated MEC (53.2%) with more than 50% mucous cells and cystic spaces, respectively low-differentiated MEC (46.8%) showing less than 50% mucous cells and cystic spaces can be subclassified. In respect of the therapeutic proceeding it should be recognized that the histopathological subclassification of MEC of the salivary glands (7) is based on morphological criteria only. It may not be equalized with a grading of malignancy since even highly differentiated MEC can grow infiltratively, sometimes osseo-destructively, to recur locally and to metastasize predominantly into the regional lymph nodes. Consequently the histopathological subclassification of MEC does not allow certain prognosis in individual cases.

Carcinoma, Mucoepidermoid↗
PubMed1994

DNA flow cytometry of reclassified subtypes of malignant salivary gland tumors.

Malignant salivary gland tumors are rare, constitute a heterogeneous group and are often difficult to diagnose histologically. This is borne out by the fact that in the present study 43.2% of 118 salivary gland tumors originally diagnosed as mucoepidermoid, acinic cell and adenoid cystic carcinomas had their original diagnosis altered upon reclassification. Patients with confirmed adenoid cystic carcinomas had a much worse prognosis than those with mucoepidermoid and acinic cell carcinomas. DNA flow cytometry showed that very few of the above mentioned three types of malignant neoplasms revealed aneuploid DNA stemlines, indicating that this is not a relevant prognostic tumor marker within the groups. However, several of the tumors that had their diagnosis changed, mostly to undifferentiated adeno- or squamous cell carcinomas, showed aneuploid DNA stemlines. The survival time of patients with aneuploid tumors was considerably reduced compared to those with diploid tumors. Among confirmed acinic cell, mucoepidermoid and adenoid cystic carcinomas the S-phase fraction was a significant prognostic factor, as it was among all tumors examined. This indicates that DNA aneuploidy and S-phase fractions are potential prognostic factors for malignant salivary gland tumors, and that DNA flow cytometry may assist the characterization of such tumors.

Aneuploidy↗
PubMed1994

Reactions of bone tissue in old rats to three different implant materials.

This study compares the bone responses of old rats when implanted with hydroxyapatite ceramic (HAC)-coated titanium, high-density HAC, and uncoated titanium. Twelve two-year-old Wistar rats were used in this study. Cylindrical implants were placed into each tibia, and the animals were killed seven, 14, 28, or 56 days after implantation. Undecalcified sections were prepared and were then stained with toluidine blue. The healing process was examined histologically, and histomorphometric measurements were made with a computer-based image analyzer to quantify the percentage of implant-bone contact. The results indicated that the HAC-coated implants were superior to the uncoated titanium implants in relation to bone contact. In the cases where the bone-free surface of HAC coating was dissolved, macrophages were often seen on the surface of the implant. Although further longitudinal data are needed to evaluate the decrease of HAC coating, in this animal model, HAC-coated implants may be useful for osseous response in bones of poor quality.

Age Factors↗
PubMed1994

Guided tissue regeneration around dental implants in immediate extraction sockets: comparison of e-PTFE and a new titanium membrane.

To evaluate the efficacy of guided tissue regeneration around exposed implant threads, 16 implants were placed into fresh extraction sockets in beagle dogs. Polytetrafluoroethylene (e-PTFE) membranes and titanium membranes were used to cover the defects around implants. A control group did not receive any membranes. Results were evaluated histologically. The average gain in bone height was 2.1 mm for e-PTFE sites, 0.8 mm for titanium membranes, and 2.9 mm for control sites. The greatest gain in bone levels was seen for two sites that received e-PTFE membranes and remained covered for the entire evaluation interval. Within the limits of this study, clinical and histologic evidence demonstrated that, when primary coverage is maintained, the use of e-PTFE membranes can significantly enhance bone regeneration around implants.

Alveolar Bone Loss↗
PubMed1993

Development and functionality of isoelastic dental implants of titanium alloys.

Two types of isoelastic endosseous dental implants were produced and their functionality was tested. One type consisted of a porous sintered TiTa30 alloy, the other had a special surface structure consisting of titanium wire loops. Their mechanical properties were optimized by the production parameter (sintering and diffusion bonding, respectively). The functionality was tested after insertion into an artificial jaw which had properties corresponding to the natural mandibular. The elastic properties of both implants were similar to the properties of the bone. In addition the implants have a safe anchorage bone ingrowth. In animal experiments using the implant with surface loops it was observed that the bone entered the loops and even extremely small surface cavities in the wire loops.

Alloys↗
PubMed1993

Prognostic value of PCNA and cytokeratins for radiation therapy of oral squamous cell carcinoma.

In a retrospective pilot study we compared morphologically the first biopsies of 20 patients suffering from oral squamous cell carcinoma (OSCC) where preoperatively performed radiation therapy [gamma rays (cobalt-60)] was successful with 20 patients who underwent the same therapy without the expected success. All specimens were formalin fixed and paraffin embedded. We performed haematoxylin and eosin staining and immunohistochemistry (ABC-method) applying broad spectrum cytokeratin, cytokeratin (CK) 1 + 2, 3 + 6, 13 and anti-proliferating cell nuclear antigen (PCNA, PC10). The specimens of the patients with success of the radiotherapy showed statistically higher levels of PCNA positive tumour cells, measured by a computerised morphometric analysis system (VIDAS). These specimens showed significantly less CK 3-6 positive tumour cells than the specimens of the patients with failure of this therapy. The difference in the content of proliferating cell nuclear antigen might explain the different results of the performed radiation therapy. The difference in cytokeratin 3 + 6 expression might be linked with the different amount of benign hyperproliferation. Prospective studies are planned to prove the results.

Adult↗
PubMed1993

Histology of laser- and high-frequency-electrosurgical incisions in the palate of pigs.

The histological effects of CO2-laser-, Nd-YAG-laser- and electrosurgical incisions were investigated in the oral mucosa of pigs. Laser- as well as electrosurgery caused necrosis by thermal effects. Undermining vacuolisation in the stratum basale and denaturation of collagenous fibers in the lamina propria were typical findings. The CO2-laser incisions were trough-like with a sharply bordered coagulation. The Nd-YAG-laser produced exclusively coagulation but no incision. Electrosurgery yielded radiating coagulation and the best ratio of depth of incision to width of coagulation.

Aluminum Silicates↗
PubMed1993

The role of early versus late removal of GTAM membranes on bone formation at oral implants placed into immediate extraction sockets. An experimental study in dogs.

The purpose of this study was to compare the effect of early versus late removal of expanded polytetrafluoroethylene (e-PTFE) membranes on bone formation at oral implants. Thirty Brånemark fixtures were placed into immediate extraction sockets with buccal bone dehiscences augmented by e-PTFE membranes. At 4 weeks, the membranes and underlying soft tissues were removed from 5 implants, but at 16 sites only the membranes were extirpated. In 9 sites, the membranes remained in place during the healing period. Sixteen weeks after fixture insertion, the sites in which the membrane was retained (MRET) showed an average of 5.2 mm of clinical bone height increase (100% of bone fill). For sites where the membrane together with underlying soft tissues were removed (MRB), the corresponding value was 2.0 mm (42% of bone fill). Implants at which only the membrane was removed (MR) showed the least clinical bone height increase (1.0 mm), resulting in 21% coverage of original threads. Histometric measurements verified that the MRET sites had the least distance from the top of the fixture to the newly formed bone level (0.4 mm). However, in contrast with the clinical findings, the histometric analyses showed that the MRB group had the greatest remaining bone defect (3.3 mm). The clinical and histometric results of the MRET group were statistically better, though, compared with those of the other two groups. Biopsies, removed from beneath the membranes, revealed slightly inflamed connective tissue, containing spicules of newly formed bone, indicating that more bone might have been created if the membranes had been retained longer.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗