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Biomedical subjects

M Hedin

Publications and source records attributed to M Hedin.

8 recordsLinked to original sources
PubMed1989

Developing solutions for dental X-ray processors.

Six developing solutions suitable for automatic X-ray processors with high developer temperature have been tested during a period of 14 days without replenishment of the chemicals. The results are presented as blackening of dental test films with an image of an aluminium step wedge (penetrometer). Both speed and contrast could be measured in this manner. Freshly mixed solutions showed marked differences in processing of films where the developers Dürr, Readymatic (Kodak) and Tetenal (Mediquipe) were best. After 14 days in the processor, the developing effect was poor for most of the tested liquids, due to atmospheric oxidation. The best images, with the least radiation, will be obtained with freshly mixed chemicals suitable for the films used. Besides a lower radiation dose to the patient, due to a short exposure time, blurring caused by the patient's moving will be reduced. Other factors such as the pack and prices must also be taken into consideration in the choice of radiographic solutions.

Color↗
PubMed1978

Surgical treatment of nasopalatine duct cysts. A follow-up study.

In a clinical-radiological study, 43 operated and histopathologically verified incisive canal cysts were subjected to follow-up investigation. The clinical investigation revealed no subjective symptoms. Abnormalities of the sensibility to the anterior part of the palate were noted in four cases, hyposensibility in three cases and hypersensibility in the fourth. The radiological investigation showed that bone regeneration occurred 1 year postoperatively at the earliest. After 3 years, two-thirds of the patients showed complete bone regeneration. Large cysts (diameter greater than 10 mm) showed the same tendency for bone regeneration as small cysts. The five patients in whom no bone regeneration had occurred were subjected to reoperation. The histologic investigation of these patients revealed scar tissue.

Adolescent↗
PubMed1975

Measurement of fine structures in roentgenograms. III. Studies on root canals of teeth.

A study of the projection of root canals of natural teeth on dental roentgenograms was carried out as a sequel to an earlier phantom study. The material consisted of extracted teeth and teeth in situ in jaw preparations. The same radiation source and focus-film distance were used throughout, but the exposure times and tube voltages were varied. The roentgenographic images of the root canals were analysed densitometrically and compared with measurements of the actual object dimensions. The root were sectioned at the level studied and their cross sections were traced and measured with the aid of a profile projector. There was good agreement between the true breadth of the canal and that projected on the film. The maximum contrast in the image of the canal and the densitometrically measured difference in substance, expressed in metal equivalents, were proportional to the depth of the canal in the direction of radiation. The breadth of the canal in the plane of the film was the same regardless of whether the tube voltage was 50, 60 or 90 kV. On the other hand, the tube voltage affected the photographic density differences between the canal and the dentine walls. Changing the voltage from 50 to 60 kV did not affect the results, but there was a highly significant difference between 90 and 50 or 60 kV. The clinical significance of tube voltage and exposure time is discussed.

Absorptiometry, Photon↗