[Zirconia and removable partial dentures]

The present paper deals with the double crown technique in removable prosthodontics. New ceramic materials like zirconia are increasingly used in combination with CAD/CAM technologies for framework fabrication of fixed prosthesis, tooth- or implant-supported. However, zirconia is also a newly accepted material in removable prosthodontics. It replaces gold alloys for the fabrication of primary telescopic crowns. The Galvanoforming technology is preferably used to fabricate the secondary crowns. The combination of both techniques and materials results in a prosthetic reconstruction of high quality, optimum fit and good biocompatibility.

A comparison between the chemical behaviour of lead-gold and lead-bismuth eutectics towards 316L stainless steel

Lead-gold eutectic (LGE) has been recently proposed as an alternative target material for high power spallation sources. In order to compare the corrosive properties of LGE to the better-studied eutectic of lead-bismuth (LBE), an isothermal twin-loop made of SS 316L was built and operated at the Institute of Physics of the University of Latvia. We have measured the concentration of steel alloying elements dissolved in both alloys at the end of two test campaigns via ICP-OES. In case of LGE, a pronounced concentration increase of Fe, Ni, Mn and Cr is found in the liquid metal, which is significantly higher compared to LBE. Similar results were obtained during complementary investigations on material samples exposed to both alloys in this twin-loop at 400 ◦C and 450 ◦C. These findings indicate that in contact with LGE, SS 316L steel suffers from substantial chemical attack. Detailed investigations using structure materials other than SS 316L have to be undertaken before qualifying LGE as a serious alternative to LBE.