Breakdown of intermediate-range order in liquid GeSe(2) at high pressure.

Studies of liquids with tetrahedral coordination, particularly during compression or quenching, have indicated the existence of distinct phases in the liquid state, distinguishable by density and local structure. In systems that exhibit critical phenomena in the supercooled state, anomalous behaviour of the compressibility is also anticipated above the critical point, as revealed by simulations of water. Liquid GeSe(2) is a potentially attractive system for studying both types of phenomena, given its two-dimensional tetrahedral structure and anomalous physical properties (including a density minimum near its melting point). Here we report in situ X-ray diffraction measurements of solid and liquid GeSe(2) at high temperature and high pressure, revealing that the structure of the liquid is sensitive to pressure and that anomalous compressibility is expected. During compression of liquid GeSe(2), the connectivity of the liquid changes from two- to three-dimensional, leading to a breakdown of the intermediate-range order. The gradual change in structure above the melting line may develop to a first-order liquid-liquid transition in the supercooled regime.

Assessment in rats of a new bioerodible bone-wax-like polymer.

Holes drilled in rats' skull, iliac crest, and tibia were filled with beeswax or with a new, wax-like, bioerodible polyorthoester (Alzamer). Empty drill-holes served as controls. In addition, beeswax and polyorthoester were deposited between the left and the right oblique abdominal muscles, respectively. In muscle, both the beeswax and polyorthoester elicited a transient foreign body reaction. The beeswax was not resorbed in bone or muscle, whereas the polyorthoester was. Bone healing was inhibited in the iliac crest and the tibiae filled with beeswax, whereas holes filled with polyorthoester healed readily.

Identification of common foreign material in postendodontic granulomas and cysts.

The present investigation was undertaken to identify commonly occurring foreign material in postendodontic periapical granulomas and cysts. 29 biopsies from such lesions with observed foreign material were routinely processed, stained with H&E, von Kossa and Calcofluor White and investigated by light, polarization and fluorescence microscopy. Applying back-scattered SEM images, the foreign material was subjected to energy dispersive X-ray analysis. 4 groups of foreign material were observed: 1. Black/brownish fragments and yellow/brown granules containing Au, Ag, Cu, Hg, Sn and Zn compatible with amalgam. 2. Fine black/brown/yellow granules compatible with endodontic sealer components revealing Ag, Ba, Bi, Cu, S, Ti and Zn. 3. Basophilic fragments compatible with Ca salts from Ca(OH), extruded periapically and containing Ca and P. 4. Elongated/rounded/oval/kidney-shaped, colourless to slightly basophilic, birefringent structures revealing C and O and with a slit-like central canal and a bright, pale-blue fluorescence specific for cellulose.

Cellulose fibers from endodontic paper points as an etiological factor in postendodontic periapical granulomas and cysts.

Histological sections of eight periapical granulomas and cysts developing after conventional endodontic therapy and displaying faintly hematoxylinophilic, birefringent foreign bodies were investigated by light and polarization microscopy, scanning electron microscopy, energy-dispersive X-ray, and chemical analysis. In addition to a variably dense mononuclear infiltrate, the granulomas and cysts revealed varying amounts of giant cells associated with the birefringent foreign bodies. These structures were identified as cellulose fibers, most probably originating from endodontic paper points, which in our opinion can be held responsible for the initiation and perpetuation of chronic postendodontic periapical lesions.

Abrasives in snuff?

The purpose of this study was to determine and calculate the inorganic contents of four brands of snuff. Visual inspection of wet snuff showed fairly large, yellow crystal-like particles. Scanning electron microscopy and X-ray dispersive (EDX) analyses were used to study both wet snuff and ashes of snuff, whereas light emission spectrography was used to determine elements in the ashes. The crystal-like particles did not dissolve in distilled water or in ethanol heated to 60 degrees C. EDX analyses showed that most elements remained in the particles after washing. The total weight percentage of inorganic material in snuff was calculated after burning dried snuff until constant weight was obtained. The ashes of snuff did not contain any crystal-like particles but consisted of a small-grained amorphous mass. The following elements were detected: Ag, Al, Ba, Ca, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, P, Pb, Si, Sr, Ti, Va, and Zr. Other elements such as rare earths were not searched for. The weight percentage of inorganic elements ranged between 12.35 +/- 0.69 and 20.95 +/- 0.81. Provided snuff is used in the same manner as chewing tobacco, and some people admit to doing so, there is a risk that its relatively high contents of inorganic material and heavily soluble salts may be conducive to excessive abrasion of teeth and restorations.

Identification of cellulose fibers in oral biopsies.

Oral biopsies comprising five periapical cysts, three cases of exuberant granulation tissue in extraction sockets and one case of a mandibular radiopaque structure, all displaying material consistent with cellulose fibers on routine histologic examination, were subjected to histochemical, polarization, fluorescence and scanning electron microscopical, energy dispersive X-ray and chemical investigations. Routine screening of periapical lesions with polarization microscopy and identification of possible cellulose fibers with Calcofluor White is advocated. Further, attention is drawn to endodontic paper point material as an etiologic factor in postendodontic periapical inflammatory processes.

Uncoated specimen of human enamel observed in the scanning electron microscope.

A 1-mm-thick section of a human premolar was acid etched and observed uncoated in the SEM at accelerating voltages of 3, 5, 10 and 15 kV. Prisms and interprismatic substance were easily distinguishable. Low-voltage operation (3 and 5 kV) gave the best results. Specimen charging was detectable at 5 kV and caused reduced image quality at 10 and 15 kV. Application of silver paste did not reduce charging appreciably. Prolonged observation at high magnification (x 10 000) resulted in contamination of the specimen with consequent charging and reduced resolution. Dental enamel seems to be a material which is well suited when uncoated for observation in the SEM. This may be due both to the high content of the relatively heavy atom calcium, giving good secondary electron emission, and possibly to a certain degree of conductivity caused by diffusible ions.