title: Stress-relieving and porcelain firing cycle influence on marginal fit of commercially pure titanium and titanium-aluminum-vanadium copings.
abstract: OBJECTIVE
  This study evaluated: (1) the marginal fit of copings fabricated from commercially pure titanium (cp Ti) and titanium-aluminum-vanadium alloy (Ti-6Al-4V) after each firing cycle for a recommended porcelain; and (2) the effectiveness of a stress-relieving treatment on the fit. The results were compared with copings made with Pd-Ag alloy submitted to the recommended porcelain firing protocol.
  
  
  METHODS
  Bovine teeth were machined for metal-ceramic crowns and die casts were obtained for waxing patterns. The firing cycle of titanium porcelain was performed on cp Ti and Ti-6Al-4V copings obtained using the Rematitan System. A stress-relieving treatment (cp Ti treated and Ti-6Al-4V treated groups) was performed on original invested castings at the first porcelain firing temperature (800 degrees C). Fit (microm) was measured in the 'as cast' condition and after each porcelain firing cycle with a traveling microscope. The values were compared using the analysis of variance and Tukey's test (P<0.05), the Pd-Ag group was compared to titanium groups using Dunnett's test (P<0.05).
  
  
  RESULTS
  The marginal fit values in the as-cast condition (initial) were 84.43 microm for Ti-6Al-4V not treated, 76.35 microm for Ti-6Al-4V treated, 86.09 microm for cp Ti not treated, 97.66 microm for cp Ti treated and 58.11 microm for Pd-Ag group. The Ti-6Al-4V, cp Ti, and Pd-Ag groups exhibit significant differences in marginal fit values when the as-cast condition (initial) was compared with those after the recommended porcelain firing protocol (by Tukey's test at 5% probability level). No significant differences were observed between stress-relieving treated and not treated groups.Significance. The firing cycles used for porcelain build-up may worsen the fit of titanium copings to values that suggest no inferences to the detriment of clinical applications.
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dentistry School, Campinas State University, Rua Campos Salles 2006/92 CEP, Piracicaba, SP 13416 310, Brazil.
authors.forename: Johnson Campideli
authors.initials: JC
authors.lastname: Fonseca
authors.forename: Guilherme Elias Pessanha
authors.initials: GE
authors.lastname: Henriques
authors.forename: Lourenço Correr
authors.initials: LC
authors.lastname: Sobrinho
authors.forename: Mário Fernando
authors.initials: MF
authors.lastname: de Góes
mesh_terms: D000497:Alloys; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D003442:Crowns; D003735:Dental Casting Technique; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D016876:Metal Ceramic Alloys; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D014025:Titanium
chemical_list: D000497:Alloys; D016876:Metal Ceramic Alloys; C031462:titanium alloy (TiAl6V4); D014025:Titanium