title: Accuracy of impression techniques for an implant-supported prosthesis.
abstract: OBJECTIVE
  This in vitro study compared the dimensional accuracy of a stone index and of two impression techniques (squared impression copings and modified squared impression copings) for implant-supported prostheses.
  
  
  METHODS
  A master cast with four parallel implant-abutment analogs and a passive framework were fabricated. Vinyl polysiloxane impression material was used for all impressions with a metal stock tray. Three groups of impressions were tested (n = 5): index (I), squared (S), and modified squared (MS). The measurement method employed was just one titanium screw tightened to the framework. The measurements (60 gap values) were analyzed using software that received the images from a video camera coupled to a stereomicroscope at 3100 magnification. The results were evaluated statistically (analysis of variance, Holm-Sidak method, α = .05).
  
  
  RESULTS
  The mean abutment/framework interface gaps were: master cast = 31.63 µm; group I = 45.25 µm; group S = 96.14 µm; group MS = 51.20 µm. No significant difference was detected among the index and modified squared techniques (P = .05).
  
  
  CONCLUSIONS
  Under the limitations of this study, the techniques modified squared and index generated more accurate casts than the squared technique.
authors.affiliation: Araraquara University Center-UNIARA, Araraquara, São Paulo, Brazil. mdelacqua@ig.com.br
authors.forename: Marcelo Antonialli
authors.initials: MA
authors.lastname: Del'Acqua
authors.forename: Alejandro Muñoz
authors.initials: AM
authors.lastname: Chávez
authors.forename: Marco Antonio
authors.initials: MA
authors.lastname: Compagnoni
authors.forename: Francisco de Assis
authors.initials: Fde A
authors.lastname: Molo
mesh_terms: D002133:Calcium Sulfate / Q000737:chemistry; D000044:Dental Abutments; D015921:Dental Implants; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation / Q000592:standards*; D018772:Dental Marginal Adaptation / Q000592:standards; D003764:Dental Materials / Q000737:chemistry; D019094:Dental Prosthesis, Implant-Supported; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D012984:Software; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque; D014741:Video Recording / Q000295:instrumentation
chemical_list: D015921:Dental Implants; D003760:Dental Impression Materials; D003764:Dental Materials; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane; D014025:Titanium; D002133:Calcium Sulfate