Zonal coulometric analysis of the corrosion resistance of dental alloys

OBJECTIVES

The corrosion resistance of a series of 51 dental alloys and pure metals was evaluated by coulometric analysis.

METHODS

The method consisted of dividing the anodic polarization curves into three separate zones: zone I, from the open-circuit potential (after 24 h immersion) up to +300 mV (SCE): zone II, from 300 mV to 700 mV (SCE): zone III, +700 mV to 1000 mV (SCE). The surfaces below the curves are integrated for each zone and the results expressed in millicoulombs (mC).

RESULTS AND CONCLUSIONS

Although the intensity of degradation in the mouth may vary from patients to patient, we think that a potential danger may occur in zones I and II in particular. Coulometric analysis reveals that: (i) the alloys for the porcelain-fused-to metal (PFM) technique have a better corrosion resistance (2.58 mC on average for the sum of the three zones, against 283.7 mC for conventional alloys): (ii) the elements Cu, Ag and Ni reduce the corrosion resistance of gold-based alloys: (iii) within the same class, single-phase alloys resist better than two-phase alloys.