title: A comparative study of the accuracy between plastic and metal impression transfer copings for implant restorations.
abstract: OBJECTIVE
  A precise transfer of the position and orientation of the antirotational mechanism of an implant to the working cast is particularly important to achieve optimal fit of the final restoration. This study evaluated and compared the accuracy of metal and plastic impression copings for use in a full-arch mandibular edentulous simulation with four implants.
  
  
  METHODS
  Metal and plastic impression transfer copings for two implant systems, Nobel Biocare™ Replace and Straumann SynOcta®, were assessed on a laboratory model to simulate clinical practice. The accuracy of producing stone casts using these plastic and metal impression transfer copings was measured against a standard prosthetic framework consisting of a cast gold bar. A total of 20 casts from the four combinations were obtained. The fit of the framework on the cast was tested by a noncontact surface profilometer, the Proscan 3D 2000 A, using the one-screw test. The effects of implant/system and impression/coping material on gap measurements were analyzed using repeated measures ANOVA.
  
  
  RESULTS
  The findings of this in vitro study were as follows: plastic copings demonstrated significantly larger average gaps than metal for Straumann (p = 0.001). Plastic and metal copings were not significantly different for Nobel (p = 0.302). Nobel had significantly larger average gaps than Straumann for metal copings (p = 0.003). Nobel had marginally smaller average gaps than Straumann (p = 0.096) for plastic copings. The system-by-screw location interaction was significant as well (p < 0.001), indicating significant differences among the four screw locations, but the location differences were not the same for the two systems. A rank transformation of the data was necessary due to the nonnormal distribution of the gap measurements. No adjustments were made for multiple comparisons.
  
  
  CONCLUSIONS
  The metal impression copings were more accurate than plastic copings when using the Straumann system, and there was no difference between metal and plastic copings for the Nobel Replace system. The system-by-screw location was not conclusive, showing no correlation within each system.
authors: Department of Restorative Dental Sciences, Division of Prosthodontics, University of Florida College of Dentistry, Gainesville, FL 32610, USA. mfernandez@dental.ufl.edu
authors: Monica A
authors: MA
authors: Fernandez
authors: Carmen Y
authors: CY
authors: Paez de Mendoza
authors: Jeffrey A
authors: JA
authors: Platt
authors: John A
authors: JA
authors: Levon
authors: Suteera T
authors: ST
authors: Hovijitra
authors: Arthur
authors: A
authors: Nimmo
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003735:Dental Casting Technique; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation*; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D007575:Jaw, Edentulous / Q000534:rehabilitation; D008334:Mandible / Q000473:pathology; D008422:Materials Testing; D008768:Methylmethacrylates / Q000737:chemistry; D003765:Models, Dental; D010969:Plastics / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D003722:Dental Alloys; D015921:Dental Implants; D003760:Dental Impression Materials; D003764:Dental Materials; C082318:GC Pattern Resin; D006047:Gold Alloys; D008768:Methylmethacrylates; D010969:Plastics; D011145:Polyvinyls; D012833:Siloxanes; C480691:aquasil; D014025:Titanium
keywords: Implant; gap; impressions; jig; misfit; prosthetic framework; screw test