title: Multitechnique characterization of CPTi surfaces after electro discharge machining (EDM).
abstract: OBJECTIVE
  The aim of this study was to comparatively assess the surface roughness parameters, the hardness, and the elemental and molecular alterations induced on CPTi surfaces after conventional finishing and finishing with electro discharge machining (EDM).
  
  
  METHODS
  A completed cast model of an arch that received four implants was used for the preparation of two grade II CPTi castings. One framework was conventionally finished (CF), whereas the other was subjected to EDM finishing. The surface morphology was imaged employing SEM. 3D surface parameters (S a, S q, S z, S ds, S dr, and S ci) were calculated by optical profilometry. The elemental composition of the treated surfaces was determined by energy dispersive X-ray analysis, whereas the elemental and chemical states of the outmost layer were investigated by X-ray photoelectron spectrometry. Surface hardness was also tested with a Knoop indenter. The results of surface roughness parameters, elemental analysis, and hardness were compared using unpaired t test (a = 0.05).
  
  
  RESULTS
  The EDM group demonstrated a rougher surface, with a significant uptake of C and Cu. The CF surface mainly consisted of TiO2. On EDM surface though, Ti was probed in different chemicals states (TiO2, Ti2O3, TiC and metallic Ti) and Cu was traced as Cu2O and CuO. Hardness after EDM was almost ten times higher than CF.
  
  
  CONCLUSIONS
  EDM significantly affected surface roughness, chemical state, and hardness properties of grade II CPTi castings in comparison with CF.
  
  
  CONCLUSIONS
  The morphological and elemental alterations of EDM-treated CPTi surfaces may strongly contribute to the reduced corrosion resistance documented for this procedure. The degradation of electrochemical properties may have further biological implications through ionic release in the oral environment.
authors.affiliation: Department of Biomaterials, School of Dentistry, University of Athens, Thivon 2, Goudi, 11527, Athens, Greece, szinelis@dent.uoa.gr.
authors.forename: Spiros
authors.initials: S
authors.lastname: Zinelis
authors.forename: Youssef S
authors.initials: YS
authors.lastname: Al Jabbari
authors.forename: Andrew
authors.initials: A
authors.lastname: Thomas
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.forename: George
authors.initials: G
authors.lastname: Eliades
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment; D003775:Dental Polishing / Q000379:methods; D055664:Electrochemical Techniques / Q000379:methods*; D006245:Hardness Tests; D006801:Humans; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D056951:Photoelectron Spectroscopy; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D003734:Dental Casting Investment; D014025:Titanium