title: The effect of Electro Discharge Machining (EDM) on the corrosion resistance of dental alloys.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the effect of Electro Discharge Machining (EDM) on the corrosion resistance of two types of dental alloys used for fabrication of implant retained superstructures.
  
  
  METHODS
  Two groups of specimens were prepared from a Co-Cr (Okta-C) and a grade II cpTi (Biotan) alloys respectively. Half of the specimens were subjected to EDM with Cu electrodes and the rest were conventionally finished (CF). The corrosion resistance of the alloys was evaluated by anodic polarization in Ringer's solution. Morphological and elemental alterations before and after corrosion testing were studied by SEM/EDX. Six regions were analyzed on each surface before and after corrosion testing and the results were statistically analyzed by paired t-test (a=0.05).
  
  
  RESULTS
  EDM demonstrated inferior corrosion resistance compared to CF surfaces, the latter being passive in a wider range of potential demonstrating higher polarization resistance and lower I(corr) values. Morphological alterations were found before and after corrosion testing for both materials tested after SEM analysis. EDX showed a significant decrease in Mo, Cr, Co, Cu (Co-Cr) and Ti, Cu (cpTi) after electrochemical testing plus an increase in C.
  
  
  CONCLUSIONS
  According to the results of this study the EDM procedure decreases the corrosion resistance of both the alloys tested, increasing thus the risk of possible adverse biological reactions.
authors.affiliation: Department of Biomaterials, School of Dentistry, University of Athens, 2 Thivon Str, Goudi 115 27, Athens, Greece.
authors.forename: Argyro
authors.initials: A
authors.lastname: Ntasi
authors.forename: Wolf Dieter
authors.initials: WD
authors.lastname: Mueller
authors.forename: George
authors.initials: G
authors.lastname: Eliades
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry; D003300:Copper; D003343:Corrosion; D003442:Crowns; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique; D003775:Dental Polishing / Q000379:methods*; D055664:Electrochemical Techniques; D004566:Electrodes; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D003734:Dental Casting Investment; D003035:Cobalt; D003300:Copper; D014025:Titanium