title: An alternative section method for casting and posterior laser welding of metallic frameworks for an implant-supported prosthesis.
abstract: OBJECTIVE
  The aim of this study was to compare the accuracy of fit of three types of implant-supported frameworks cast in Ni-Cr alloy: specifically, a framework cast as one piece compared to frameworks cast separately in sections to the transverse or the diagonal axis, and later laser welded.
  
  
  METHODS
  Three sets of similar implant-supported frameworks were constructed. The first group of six 3-unit implant-supported frameworks were cast as one piece, the second group of six were sectioned in the transverse axis of the pontic region prior to casting, and the last group of six were sectioned in the diagonal axis of the pontic region prior to casting. The sectioned frameworks were positioned in the matrix (10 N.cm torque) and laser welded. To evaluate passive fit, readings were made with an optical microscope with both screws tightened and with only one-screw tightened. Data were submitted to ANOVA and Tukey-Kramer's test (p < 0.05).
  
  
  RESULTS
  When both screws were tightened, no differences were found between the three groups (p > 0.05). In the single-screw-tightened test, with readings made opposite to the tightened side, the group cast as one piece (57.02 +/- 33.48 mum) was significantly different (p < 0.05) from the group sectioned diagonally (18.92 +/- 4.75 microm) but no different (p > 0.05) from the group transversally sectioned (31.42 +/- 20.68 microm). On the tightened side, no significant differences were found between the groups (p > 0.05).
  
  
  CONCLUSIONS
  Results of this study showed that casting diagonally sectioned frameworks lowers misfit levels of prosthetic implant-supported frameworks and also improves the levels of passivity to the same frameworks when compared to structures cast as one piece.
authors.affiliation: University of São Paulo, Dental School of Ribeirão Preto, Department of Dental Materials and Prosthodontics, Sao Paulo, Brazil.
authors.forename: Fábio Afrânio
authors.initials: FA
authors.lastname: de Aguiar
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Tiossi
authors.forename: Renata Cristina Silveira
authors.initials: RC
authors.lastname: Rodrigues
authors.forename: Maria de Gloria Chiarello
authors.initials: Mde G
authors.lastname: Mattos
authors.forename: Ricardo Faria
authors.initials: RF
authors.lastname: Ribeiro
mesh_terms: D001641:Bicuspid; D002858:Chromium Alloys / Q000737:chemistry*; D000044:Dental Abutments; D003735:Dental Casting Technique; D019094:Dental Prosthesis, Implant-Supported; D012994:Dental Soldering / Q000379:methods; D003779:Denture Design; D003781:Denture Retention; D003830:Denture, Partial, Fixed; D006801:Humans; D007834:Lasers; D008422:Materials Testing; D008963:Molar; D013499:Surface Properties; D019415:Torque
chemical_list: D002858:Chromium Alloys