brass and Foreign-Bodies

The radiological determination of foreign objects in corpses can be difficult if they are fragmented or deformed. With multislice computed tomography, radiodensities--referred to as Hounsfield units (HU)--can be measured. We examined the possibility of differentiating 21 frequently occurring foreign bodies, such as metals, rocks, and different manmade materials by virtue of their HU values. Gold, steel, and brass showed mean HU values of 30671-30710 (upper measurable limit), mean HU values for steel, silver, copper, and limestone were 20346, 16949, 14033, and 2765, respectively. The group consisting of objects, such as aluminum, tarmac, car front-window glass, and other rocks, displayed mean HU values of 2329-2131 HU. The mean HU value of bottle glass and car side-window glass was 2088, whereas windowpane glass was 493. HU value determination may therefore help in preautopsy differentiation between case-relevant and irrelevant foreign bodies and thus be useful for autopsy planning and extraction of the objects in question.

Topics: Aluminum; Copper; Foreign Bodies; Forensic Pathology; Glass; Gold; Humans; Minerals; Radiometry; Silver; Steel; Tomography, X-Ray Computed; Zinc

The basic mechanism of dental amalgam corrosion has been thoroughly studied during the last 50 years by various experimental techniques, most often carried out in vitro. Electrochemical methods were extensively employed, and it was recognized that a gradual dealloying of the more electroactive components, Zn, Sn, and to a lesser extent Cu, contributed to change the surface composition. It is also well known that, in all circumstances, galvanic coupling threatens the longevity of the restoration. Among the patients examined at the hospital attached to the Department of Dental Surgery of the Paris 5 University, the authors observed, in a few exceptional circumstances of defective restorations, a release of liquid metal droplets in the surrounding tissue. These particles were identified as elemental mercury. This unexpected phenomenon was the result of the use of a low-silver-content alloy, combined with an enhanced corrosion process due to galvanic coupling with a silver alloy crown and brass screw-posts. In the described clinical case, the tooth, which had to be extracted, was axially sliced for observation by scanning electron microscopy coupled with elemental analysis by X-ray fluorescence energy dispersive spectroscopy. The observations showed a dramatic corrosion of the amalgam matrix with the formation of porosity even in the bulk of the material. Superposition of the element mappings proved (1) the electrochemical coupling of the amalgam with the silver-based crown, (2) the decalcification of the dentin, and (3) the formation of tin oxychloride precipitates in the matrix porosities and the interfacial gaps. These experimental results corroborate the corrosion mechanisms described hereupon. They support the current national and international recommendations for the dental amalgam formulation and for a rigorous professional practice.

Topics: Adult; Copper; Corrosion; Crowns; Dental Amalgam; Electrogalvanism, Intraoral; Electron Probe Microanalysis; Foreign Bodies; Humans; Mercury; Periapical Tissue; Porosity; Silver; Tin; Tooth Extraction; Zinc

Topics: Brain Stem; Copper; Foreign Bodies; Humans; Zinc