title: Comparative study of two commercially pure titanium casting methods.
abstract: The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior.
  
  
  OBJECTIVE
  This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure.
  
  
  METHODS
  72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05).
  
  
  RESULTS
  Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted.
  
  
  CONCLUSIONS
  Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.
authors.affiliation: Department of Dental Materials and Prosthodontics, Ribeirão Preto Dental School, University of São Paulo, Ribeirão Preto, SP, Brazil. renata@forp.usp.br
authors.forename: Renata Cristina Silveira
authors.initials: RC
authors.lastname: Rodrigues
authors.forename: Adriana Claudia Lapria
authors.initials: AC
authors.lastname: Faria
authors.forename: Iara Augusta
authors.initials: IA
authors.lastname: Orsi
authors.forename: Maria da Gloria Chiarello de
authors.initials: Mda G
authors.lastname: Mattos
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Macedo
authors.forename: Ricardo Faria
authors.initials: RF
authors.lastname: Ribeiro
mesh_terms: D002858:Chromium Alloys / Q000737:chemistry*; D003734:Dental Casting Investment; D003735:Dental Casting Technique; D016734:Dental Clasps; D003781:Denture Retention; D003832:Denture, Partial, Removable; D008422:Materials Testing; D016062:Porosity; D011312:Pressure; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*; D014618:Vacuum
chemical_list: D002858:Chromium Alloys; D003734:Dental Casting Investment; D014025:Titanium