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Biomedical subjects

W Wiedemann

Publications and source records attributed to W Wiedemann.

At least 19 recordsLinked to original sources

Effect of pore topology on the remineralization rate of surface-softened enamel and synthetic hydroxyapatite: an experimental comparison and mathematical model.

Experiments with surface-softened synthetic hydroxyapatite show similar remineralization rates as surface-softened human enamel. The mineral gain with respect to time relates to parameters governing the precipitation of mineral in the specimens. A mathematical model regarding the mineral precipitation on the pore surface is fitted to the experimental values. We obtained comparable precipitation rates for apatite and tooth enamel. The geometry of the pores, however, proved to be different: a mostly tube-like pore structure must be attributed to demineralized enamel, while the synthetic hydroxyapatite specimens remineralize like a ramified, crack-like microstructure of pores.

Chi-Square Distribution

Increased interleukin-1 beta (IL-1 beta) concentration in gingival tissue from periodontitis patients.

Human gingival tissues from periodontitis patients were found to contain from 126 fg/mg to 2161 fg/mg interleukin-1 beta as determined by a sensitive enzyme linked immunoassay. No IL-1 beta could be found in normal gingival tissue. This finding may have important consequences relevant to connective tissue destruction and episodes of alveolar bone resorption characteristic of chronic periodontitis.

Adult

[Enhancement of bite-wing radiographs by digital image processing].

Extracted premolars with an initial approximal caries were subjected to radiographic and histological examination. Radiographs were taken with the rectangular technique as used for bite-wing radiographs. Digital image processing was found to enhance the image information so that the border of caries lesions as well as histological structures, Retzius lines and Hunter Schreger stripes, within the body of the lesions were well defined. This helps to distinguish initial caries from depressions in the tooth surface.

Dental Caries

[Digital image processing in the radiographic diagnosis of caries].

Used with x-ray films of entire teeth, digital image processing renders visible not only the contours of initial carious lesions but even histological enamel structures. In over 90% of those cases in which the lesions were deeper than one third of the enamel thickness at least the Hunter-Schreger lines were visible. This improvement in the informative value of x-ray images facilitates the therapeutic decision making process.

Dental Caries

[Ultrasound-guided fine-needle puncture of the thyroid].

If properly performed, modern high-resolution real-time ultrasonography will disclose subtle differences in the texture of thyroid tissue and thereby enable the examiner to suggest a diagnosis. Nevertheless, there is often a need for a more specific diagnosis of solid or semisolid thyroid lesions - especially when the lesion might be malignant. Ultrasonically guided fine-needle aspiration biopsy (UG-FNB) allows a final cytological and/or histological diagnosis to be made in patients with benign or malignant space-occupying growths even if they are small. In its simplest form, thyroid nodules (diameter greater than 1.5 cm) with a uniform sonographic texture are punctured blind after determination of the site and size of the lesion on the basis of ultrasonic imaging. When the lesion is small and deeply situated (diameter less than or equal to 1.5 cm), this method will not be sufficiently accurate and more precise needle guidance is mandatory. In ultrasonically guided fine-needle puncture, the idea is to place the tip of an appropriate needle safely and accurately in the suspect lesion, so that representative specimens of solid tissue or fluid can be obtained and technical failures reduced. The main indication for biopsy of the thyroid gland is to differentiate between benign and malignant tumors. To compare the accuracy of conventional puncture techniques and ultrasonically guided puncture methods, 835 patients with benign or malignant space-occupying growth (even the small ones) were examined simultaneously with conventional and ultrasonically guided fine-needle aspiration biopsy over a period of 3 years (prospectively). Our results showed a significant difference in the sensitivity between conventional puncture without sonographic guidance and ultrasonically guided puncture techniques performed on patients with small and very small lesions (phi less than 2 cm). The size, macroscopic structure, and topographic-anatomical localization of the lesions were found to influence the diagnostic accuracy of the puncture techniques. UG-FNB is an excellent, effective, safe and painless method of treating uncomplicated thyroid cysts; it should be considered an alternative to surgery, if there are no clinical and cytological findings indicating malignancy and no severe space-occupying complications. Since the tip of the needle can be visualized on the scan, the needle may be advanced or withdrawn during aspiration so it is possible to empty the cyst completely. The use of ultrasound in the follow-up of patients with thyroid cyst puncture is mandatory to evaluate the results. Surgical therapy should be reserved for large cysts causing space-occupying complications.

Biopsy, Needle

Enhancement of in-vivo remineralization of approximal initial caries in man by an organic and inorganic remineralization agent.

Changes of mineral content in the approximal enamel of the teeth were determined in situ with quantitative bite-wing radiography. Geometric coincidence of the base line and control radiographs was achieved with an optical adjusting device for the X-ray tube and for exact re-location of the film to the dentition. Radiographs were evaluated with digital image-processing. To five subjects, inorganic remineralization solution containing Ca, Sr, phosphate and tartrate was applied twice a day and to another 6 persons a solution containing aminofluoride (Elmex Fluid, Gaba Int.) every third day: both for 3 weeks. There was no net mineral uptake in the 15 lesions of the inorganic group but a marked increase of mineral in the 13 lesions of the other group. Discrepancy with findings of other workers may be due to the geometry of the interdental space with long diffusion distances in the dental plaque.

Adult

[Metastatic differentiated thyroid cancer. Diagnostic accuracy of thyroglobulin-RIA in comparison with 131I-whole body scintigraphy].

In a retrospective analysis in patients with differentiated thyroid carcinoma, the diagnostic validities of 131I whole-body scans and radioimmunologic determinations of thyroglobulin (hTg) are compared with special regard to late metastases. Metastases were found in 83 out of 311 patients with differentiated thyroid carcinoma. In two thirds of the cases, these were primary metastases while in the remaining third of the cases, metastases developed in later follow-up with a mean time of latency of 3.3 years. While about 70% of the early metastases could bei detected by 131I scintigraphy, this percentage amounted to only 40% in late metastases. With a diagnostic sensitivity of 90%, hTg-RIA was clearly superior in the detection of early as well as of late metastases. hTg was measurable, however, only in iatrogenous hypothyroidism in 4 out of 49 cases. Based on these results and an analysis of the literature, a program for follow-up of differentiated thyroid carcinoma is proposed. The hTg-RIA is thereby used as an alternative to 131I scintigraphy in the late phase of follow-up after complete ablation of any thyroid tissue.

Adenocarcinoma