Corrosion and metallurgical study of some porcelain fused to metal alloys

In order to evaluate the corrosion behavior of some dental alloys to be applied as base-metal for PFM, electrochemical technique and metallurgical investigation were used. Potentiodynamic and potentiostatic tests were carried out under deaerated and aerated conditions in 1 percent NaCl solution. The results have shown that Ni-Cr alloy has a superior corrosion resistance under deaerated conditions, whereas Co-Cr alloy has a stronger tendency to passivation under aerated conditions. Fe-Cr alloy has demonstrated a poor performance. The results were analyzed on compositional and microstructural bases

Effect of reporcelainization on the bond strength between non-precious alloys and porcelain

Porcelain fracture over non-precious crown copings is a common clinical disaster. It occurs always during cementation procedure or short after cementation and cause a great problem for the clinician. Repairing of fractured porcelain takes place if the fracture happens after cementation in the patient mouth. If the fracture happens during check up for cementation, the clinician immediately sends the fractured crown or bridge to the laboratory for correction. The correction by the laboratory is done through reapplication of porcelain on the fractured area and firing it again [reporcelainization]. The laboratory may sandblast the bare area before reapplication of porcelain, or not, exposing the restoration to the effect of the multiple firings. This problem is of great importance since till now there is lack of literature that investigates this point, especially the relationship between reapplication of porcelain on metal surface after porcelain failure and the new bond strength between the reapplied porcelain and metal