title: Treatment of multiple ceramic alloys before recasting.
abstract: BACKGROUND
  Dental laboratories often reuse dental casting alloys by recasting them, but the processing methods before recasting require further research.
  
  
  OBJECTIVE
  The purpose of the study was to determine the treatment methods to remove the surface contamination of the previously melted alloys before recasting.
  
  
  METHODS
  Cobalt-chromium (Co-Cr), commercially pure titanium (CP Ti), palladium-copper-gallium (Pd-Cu-Ga), and gold-platinum (Au-Pt) ceramic alloys were investigated in the present study. Field emission scanning electron microscopy, energy-dispersive x-ray spectroscopy (EDAX), and x-ray photoelectron spectroscopy (XPS) were used to evaluate the changes in the surface structures and compositions of Co-Cr, CP Ti, Pd-Cu-Ga, and Au-Pt ceramic alloys after airborne-particle abrasion and immersion in various chemical solutions for different time periods. The data obtained by EDAX and XPS were statistically analyzed by Kruskal-Wallis and Nemenyi tests (α=.05).
  
  
  RESULTS
  By using appropriate mechanical and chemical treatment procedures, the contamination content of previously cast ceramic alloys was found to be below the detection limits of EDAX and XPS. The statistical results showed that, compared to the control group (new alloys after polishing), the impurity element was not detected after being treated with these methods, which was not statistically different to control group.
  
  
  CONCLUSIONS
  The surface contamination of ceramic alloys was effectively removed by using certain mechanical and/or chemical treatment methods. Within the limitations of the present study, the most appropriate ways to treat ceramic alloys before recasting were as follows: (1) for Co-Cr ceramic alloys: Al2O3 airborne-particle abrasion and immersion in aqua regia for 15 min; (2) for CP Ti ceramic alloys: Al2O3 airborne-particle abrasion and immersion in 65% HNO3 and 40% HF 1:7 (V/V) for 60 min; (3) for Pd-Cu-Ga ceramic alloys: glass bead airborne-particle abrasion and immersion in 40% HF solution for 30 min; and (4) for Au-Pt ceramic alloys: glass bead airborne-particle abrasion.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Fujian Medical University, Fuzhou, Fujian, China.
authors.forename: Honglei
authors.initials: H
authors.lastname: Lin
authors.forename: Hai
authors.initials: H
authors.lastname: Zhang
authors.forename: Xiurong
authors.initials: X
authors.lastname: Li
authors.forename: Hui
authors.initials: H
authors.lastname: Cheng
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry*; D003734:Dental Casting Investment / Q000737:chemistry*; D003735:Dental Casting Technique; D045662:Dental Etching / Q000379:methods; D003764:Dental Materials / Q000737:chemistry; D004577:Electron Probe Microanalysis; D004866:Equipment Contamination; D017743:Equipment Reuse; D005708:Gallium / Q000737:chemistry; D005898:Glass / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D006851:Hydrochloric Acid / Q000737:chemistry; D006858:Hydrofluoric Acid / Q000737:chemistry; D007101:Immersion; D008855:Microscopy, Electron, Scanning; D017942:Nitric Acid / Q000737:chemistry; D010165:Palladium / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D002858:Chromium Alloys; D003722:Dental Alloys; D003734:Dental Casting Investment; D003764:Dental Materials; D006047:Gold Alloys; D017942:Nitric Acid; D010984:Platinum; D010165:Palladium; D003300:Copper; D005708:Gallium; D014025:Titanium; D000537:Aluminum Oxide; D006851:Hydrochloric Acid; D006858:Hydrofluoric Acid; C022102:aqua regia