Abstract:

Objective

To investigate the influence of recasting on the electrochemical corrosion properties of the Ni-Cr alloy for porcelain-fused-to-metal restoration in artificial saliva.

Methods

Five groups of cylindrical specimens ［（Φ=（4.02 ± 0.04）mm，l=（8.00 ± 0.07）mm］were made by casting Ni-Cr alloys for porcelain-fused-to-metal restoration successively for 1， 2，3， 4 and 5 times （Generation Ⅰ-Ⅴ）， respectively. One undersurface of the specimen was polished using standard metallurgical procedures with wet aluminum oxide papers， the other undersurface was welded with copper wires. The specimens were embeded with polymethyl methacrylate with the testing surfaces exposed. The electrochemical corrosion behavior of the recasted Ni-Cr alloys was studied by potentiodynamic polarization in artificial saliva ［t=（37.0 ±1.0）℃，pH=7.4±0.1］ according to ISO 10271（2001） to measure the corrosion potential （Ecorr），breakdown potential （Ep）， polarization resistance （Rp） and self-corrosion current density（Icorr）.The surface characteristics of the specimens were observed after test by scanning electron microscope. The experimental data were analysed by One-way ANOVA and Dunnett-t test.

Results

It was found that varieties of five generations of specimen in Ecorr， Ep， Rp， Icorr have no statistical significant differences （P ＞0.05）. Dunnett-t test demonstrated that there were no differences except that Ep of Ⅱwas greater than Ⅰ （P=0.23）. Pitting corrosion on the alloy surface showed no differences among the five groups.

Conclusion

Ni-Cr casting alloy for porcelain-fused-to-metal restoration can be reused after five times remelting in term of electrochemical corrosion.

Key words: Recasting, Ni-Cr casting alloy, Electrochemical corrosion