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Three types of amalgam, one conventional, ANA 68, and two with high copper content, Dispersalloy (dispersed type) and ANA 2000 (single composition type), were investigated. The amalgams were immersed for periods of 7 wk at a time, up to 35 wk, in 23 ml (37 degrees C) of 0.9% NaCl aqueous solutions and in 0.9% NaCl solution buffered with NaH2PO4 (8.8 mM) and Na2HPO4 (1.2 mM). The amalgam specimens were embedded in epoxy resin. The surface area of amalgam exposed to the solutions was 0.2 cm2 for each specimen. Every 7 wk the corrosion potential was measured, the amalgam specimens lightly brushed with a soft toothbrush, and the solutions renewed. After 14-21 wk and 35 wk the currents during anodic polarization sweeps over the amalgams were recorded. The corrosion potential for the high-Cu amalgams was somewhat more positive (noble) in the phosphate buffered solution than in the non-buffered solution during the 35 wk of corrosion. The phosphate buffer reduced the reactivity of the amalgams during anodic polarization. Corrosion made the amalgams more passive during the anodic polarization. However, all the elements leached from the amalgams into the solutions throughout the entire experiment.

One conventional amalgam and two amalgams with a high copper content were stored in 0.9% NaCl solution buffered with phosphate to pH 6. In one experimental series the amalgams were placed in contact with a gold alloy. Every 7 weeks the solutions were changed and analyzed with regard to elements released from the amalgams. The microstructure of the specimens was studied in a scanning electron microscope before immersion and after 7 and 35 weeks in the solution. All the amalgams corroded along the grain boundaries in the gamma 1 phase. Corrosion was greatest in the gamma 2 phase of ANA 68, in the eta phase of ANA 2000 and in the reaction zone (eta + gamma 1) surrounding the Ag-Cu-eutectic particles of Dispersalloy. The microstructure of the corroded amalgams showed similarities to amalgams corroded in vivo. The change in microstructure observed in cross-sections of the corroded specimens was related to the amounts of corrosion products released into the saline solution.

A collaborative study was conducted to compare a proposed LST-MUG method with the AOAC official method for Escherichia coli detection. E. coli produces an enzyme, beta-glucuronidase, which cleaves the substrate, 4-methyl-umbelliferyl-beta-D-glucuronide (MUG), to yield a fluorescent end product. Incorporation of the MUG substrate into lauryl tryptose broth (LST) enables a rapid quantitative method for screening E. coli, which is detected by fluorescence of the medium under longwave UV light. In this collaborative study, 5 food samples, 2 frozen (entree sauce/gravy and dairy topping) and 3 chilled (hamburger, pork sausage, and cheese), were tested for E. coli detection by 17 collaborating laboratories. Results indicate that the LST-MUG method is equal to or better than the current AOAC method for detecting E. coli. The LST-MUG method has been adopted official first action.

A new rapid slide agglutination test (Amniostat-FLM/AFLM) for amniotic fluid phosphatidylglycerol has been developed. One hundred ninety-three samples of amniotic fluid were tested for lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol by thin-layer chromatography and fluorescence polarization and compared with the AFLM. All four tests agreed in 123/193 cases. Phosphatidylglycerol and AFLM were concordant in 176/193 cases. From these samples, data were available on 105 neonates, of whom 74 were delivered within 72 hours of amniocentesis. All positive AFLM tests were associated with absence of hyaline membrane disease, of 22 negative tests, eight babies had hyaline membrane disease. Thus, preliminarily, it appears that this is a useful, rapid test for assessing fetal lung maturity, which like other tests is reliable when indicating maturity but has a high incidence of falsely immature results.

Amalgam specimens were immersed for 30 days in 1) water, 2) 0.9% NaCl in water, 3) 0.9% NaCl and 10 mM phosphate buffer in water, and 4) 0.9% NaCl, 7.7 mM phosphate, and 6.1 mM citric acid in water. The solutions were stored in stoppered glass tubes. Hg-drops were immersed in solutions 1, 2, and 3. The concentration of mercury vapor in the air above the solutions was measured once a day. After 30 days the amounts of Cu, Zn, Hg, and Ag in the solutions were analyzed by atomic absorption spectrophotometry. The results showed that 0.9% NaCl alone or in combination with the additives increased the amounts of elements released into the solutions. The concentration of Hg0 in the glass tubes increased with the amount of Hg in the solutions, with the exception of solution No. 3, from which significantly less Hg0 evaporated. The results indicate that the composition of the saliva, oral hygiene and dietary factors may be determinants of Hg0 emission from amalgams in the oral cavity.

This study investigated the occurrence of corrosion associated with the use of metallic implants to stabilize jaw fractures. Three different types of plates, Co-Cr and Ni-Cr alloys and Titanium, were connected in vivo to the mandibular bone surface of monkeys (Cercopithecus aethiops). The animals were killed after 3 and 6 months. The mucous membrane and bone tissue were analysed for concentrations of Co, Cr, Ni, Mo, Al, and Ti by atomic absorption spectrophometry and a radiochemical neutron activation technique. With the exception of Ti, higher concentrations of all the above elements were found in the tissue near the implants when compared with contralateral controls. However, no signs of corrosion, macroscopic or microscopic, were observed on the surface of the implants.