title: The effect of metal recasting on porcelain-metal bonding: a force-to-failure study.
abstract: BACKGROUND
  Noble dental alloys are commonly remelted in the dental laboratory, but the effect of repeated casting on porcelain bond strength requires further documentation.
  
  
  OBJECTIVE
  The purpose of this study was to determine if casting up to 3 times affected metal ceramic bond strength for 3 noble alloys using methodology in ANSI/ADA Specification No. 38.
  
  
  METHODS
  Representative high-gold (Brite Gold XH), gold-palladium (W-5), and palladium-silver (IPS d.SIGN 53) alloys were cast into metal strips (25 x 3 x 0.5 mm), using torch melting. IPS InLine porcelain with overall dimensions of 8 x 3 x 1.1 mm was centrally applied on each strip. Metal ceramic specimens were also prepared after each alloy was melted a second and third time. There were 12 specimens in each of the 9 groups. Force to failure and porcelain bond compatibility index (tau(b)) were determined for each specimen, and statistical comparisons were made using the Ryan-Einot-Gabriel-Welsch multiple range test (experimental alpha=.05). Fractured specimens were examined with a scanning electron microscope.
  
  
  RESULTS
  Mean values of tau(b) for specimen groups ranged from 40.6 to 48.2 MPa, and there were no significant differences among the 3 alloys after the first casting. For the high-gold alloy, tau(b) was significantly different for the first and third castings. Increases in size and frequency of interfacial voids were observed with the SEM when all alloys were cast 2 additional times.
  
  
  CONCLUSIONS
  All 3 alloys had adequate porcelain bond strength (>25 MPa). The bond strength for the high-gold alloy was significantly greater for the third casting than for the first casting.
authors.affiliation: College of Dentistry, The Ohio State University, Columbus, Ohio, USA.
authors.forename: Ruohong
authors.initials: R
authors.lastname: Liu
authors.forename: William M
authors.initials: WM
authors.lastname: Johnston
authors.forename: Julie A
authors.initials: JA
authors.lastname: Holloway
authors.forename: William A
authors.initials: WA
authors.lastname: Brantley
authors.forename: Tridib
authors.initials: T
authors.lastname: Dasgupta
mesh_terms: D003722:Dental Alloys; D001840:Dental Bonding; D003735:Dental Casting Technique; D003799:Dental Stress Analysis; D017743:Equipment Reuse; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D010165:Palladium
chemical_list: D003722:Dental Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; C051993:palladium-silver alloy W1; D010165:Palladium