title: Effects of investment type and casting system on permeability and castability of CP titanium.
abstract: BACKGROUND
  Several factors, such as casting systems and investment properties, are important to obtain a sound titanium casting. Although various casting systems and investments for titanium are commercially available, their effects on CP titanium castability are not clear.
  
  
  OBJECTIVE
  The purpose of this study was to determine permeability of investments and to evaluate the effects of investment type and casting system on titanium castability.
  
  
  METHODS
  Three investments for titanium (experimental gypsum-bonded investment, Selevest CB, and Speed Titan) and 4 titanium casting systems (Cyclarc, Ti-Cascom, Vulcan T, and Ticast Super R) were used. Permeability was measured using a flow meter and argon gas at 0.1, 0.2, and 0.3 MPa. Castability was calculated as the percentage of reproduced holes compared to a perforated wax pattern. Data for castability and permeability were analyzed separately with 2-way ANOVA and the Tukey HSD test (alpha=.05).
  
  
  RESULTS
  The ANOVA for permeability and castability showed significant interaction (P<.001 and P=.004, respectively). Differences in permeability among the 3 investments increased with a higher gas pressure. Permeability of the experimental investment at each pressure level was significantly greater than that of the other investments, except for Speed Titan at 0.1 MPa (P<.05). The permeability of Selevest CB at each pressure level was significantly less than that of the other investments (P<.05). Cyclarc and Ti-Cascom specimens were not significantly different, in terms of castability, using the investments evaluated, but castability of Vulcan T and Ticast specimens varied significantly by the investment used (P<.05).
  
  
  CONCLUSIONS
  Within the limitations of this study, investment type, pressure level, and their combinations influenced permeability. Castability of titanium was influenced by investment type, casting system, and their combinations. The investment with the highest permeability did not demonstrate the best result for castability.
authors.affiliation: Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan.
authors.forename: Fazal
authors.initials: F
authors.lastname: Reza
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Takahashi
authors.forename: Naohiko
authors.initials: N
authors.lastname: Iwasaki
authors.forename: Yukimichi
authors.initials: Y
authors.lastname: Tamaki
mesh_terms: D000704:Analysis of Variance; D003734:Dental Casting Investment / Q000737:chemistry / Q000145:classification*; D003735:Dental Casting Technique; D003760:Dental Impression Materials / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design / Q000379:methods*; D006801:Humans; D008669:Metallurgy; D010539:Permeability; D018709:Statistics, Nonparametric; D014025:Titanium / Q000737:chemistry*
chemical_list: D003734:Dental Casting Investment; D003760:Dental Impression Materials; D003764:Dental Materials; D014025:Titanium