– The galvanic current densities between gold, amalgam and cobalt‐chromium, three different classes of dental alloys, were determined in vitro in artificial saliva kept at 35°C. The maximum current density of 200 μA/drn2was obtained between the conventional amalgam and a type III gold alloy. Galvanic currents of lesser magnitude could also be measured between amalgams high in copper and the other alloys. No measurable current densities were obtained between gold alloys and between gold and cobalt‐chromium alloy with the exception of a casting and a solder gold alloy commonly used in combination.

A key event in bone resorption is the attachment of osteoclasts on the bone surface. Accumulating data supports the notion that this interaction involves the matrix protein osteopontin on the bone surface interacting with a receptor of the integrin family (alpha v beta 3) at the osteoclast clear zone. Based on the recent observation that osteopontin phosphorylation appears to be required for this interaction, it is of considerable interest to delineate the structural requirements for osteopontin-mediated cell attachment. Although binding of isolated osteoclasts to osteopontin-coated surfaces involves the alpha v beta 3 integrin, this system suffers from considerable disadvantages to allow detailed studies in this respect. We have therefore turned to another cell system, HL-60 promyelocytic leukemia cells, to address these questions. In the presence of the phorbol ester TPA (10 nM) and 1,25-dihydroxyvitamin D3 (100 nM), 90% of the HL-60 cells became adherent within 24 hours and exhibited a macrophage-like appearance. Under these conditions, the osteopontin mRNA levels was elevated around 60-fold compared to the control, non-adherent cells. The absolute requirement of de novo osteopontin synthesis for the TPA and 1,25-vit D3-induced HL-60 cell adhesion was demonstrated by neutralisation of adhesion using an anti-osteopontin polyclonal antibody as well as following transfection of an antisense osteopontin phosphorothioate-modified oligonucleotide. Finally, inhibition of induced HL-60 cell adhesion by an RGD-containing peptide or by an antibody to the alpha v beta 3 integrin complex suggested that the cell-derived osteopontin interacts with this integrin. It is concluded that HL-60 cells induced to differentiate with the combination of TPA and 1,25-vit D3 can be utilised as a model system to delineate structural requirements involved in the interaction between osteopontin and the alpha v beta 3 integrin.

– Galvanic series for different metals in different electrolytes have been published, but never for dental alloys in artificial saline solution. The material classes studied are amalgam, gold alloy, nickel alloy, chromium cobalt casting alloy and temporary crown form. The electrogalvanic potentials were measured and determined in reference to a hydrogen electrode (H2/H+) arbitrarily defined as zero. A galvanic series of the tested materials was arranged in order of their potentials.

The influence of different stone mixing agents, impression materials and lubrication methods on the surface hardness of a stone die material has been evaluated. For one impression material the dimensional effect of the mixing agents and lubrication on the dies was also studied. The stone die material was mixed with water or a gypsum hardener and allowed to set on surfaces of glass, agar-agar, polyether, polysulfide and silicone impression materials. The lubrication methods for the stone were mineral oil, water soluble lubricant and mineral oil followed by water soluble lubricant. The surface hardness was measured according to the Brinell test. The Brinell test was chosen after a comparative study of the Brinell, Vickers and Knoop hardness test methods. The results showed that gypsum hardener was preferable to distilled water. The impression materials appear to have influence on the surface hardness of stone. The effect differed on water mixed and hardener mixed stone which emphasizes the importance of the mixing agent. All lubrication decreased the surface hardness of stone. With hardener mixed stone the combination of mineral oil followed by water soluble lubricant seemed preferable. Neither the gypsum hardener nor the lubrication influenced the dimension of the stone die material.

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