title: Precision of fit between implant impression coping and implant replica pairs for three implant systems.
abstract: BACKGROUND
  The fabrication of an accurately fitting implant-supported fixed prosthesis requires multiple steps, the first of which is assembling the impression coping on the implant. An imprecise fit of the impression coping on the implant will cause errors that will be magnified in subsequent steps of prosthesis fabrication.
  
  
  OBJECTIVE
  The purpose of this study was to characterize the 3-dimensional (3D) precision of fit between impression coping and implant replica pairs for 3 implant systems. The selected implant systems represent the 3 main joint types used in implant dentistry: external hexagonal, internal trilobe, and internal conical.
  
  
  METHODS
  Ten impression copings and 10 implant replicas from each of the 3 systems, B (Brånemark System), R (NobelReplace Select), and A (NobelActive) were paired. A standardized aluminum test body was luted to each impression coping, and the corresponding implant replica was embedded in a stone base. A coordinate measuring machine was used to quantify the maximum range of displacement in a vertical direction as a function of the tightening force applied to the guide pin. Maximum angular displacement in a horizontal plane was measured as a function of manual clockwise or counterclockwise rotation. Vertical and rotational positioning was analyzed by using 1-way analysis of variance (ANOVA). The Fisher protected least significant difference (PLSD) multiple comparisons test of the means was applied when the F-test in the ANOVA was significant (α=.05).
  
  
  RESULTS
  The mean and standard deviation for change in the vertical positioning of impression copings was 4.3 ±2.1 μm for implant system B, 2.8 ±4.2 μm for implant system R, and 20.6 ±8.8 μm for implant system A. The mean and standard deviation for rotational positioning was 3.21 ±0.98 degrees for system B, 2.58 ±1.03 degrees for system R, and 5.30 ±0.79 degrees for system A. The P-value for vertical positioning between groups A and B and between groups A and R was <.001. No significant differences were found for vertical positioning between groups B and R. The P-value for rotational positioning between groups A and B and between groups A and R was <.001. No significant differences were found for rotational positioning between groups B and R.
  
  
  CONCLUSIONS
  The results of the study confirmed that implant systems differ in precision of fit. Vertical precision between paired implant components is a function of joint type and the tightening force applied to the guide pin. The magnitude of vertical displacement with applied torque is greater for conical connections than for butt joint connections. The rotational freedom between paired components is unique to the implant system and is presumably related to the machining tolerances specified by the manufacturer.
authors: National University of Singapore, Faculty of Dentistry, Singapore.
authors: Roxanna J
authors: RJ
authors: Nicoll
authors: Albert
authors: A
authors: Sun
authors: Stephan
authors: S
authors: Haney
authors: Ilser
authors: I
authors: Turkyilmaz
mesh_terms: D000704:Analysis of Variance; D003442:Crowns; D015921:Dental Implants; D003761:Dental Impression Technique / Q000295:instrumentation; D017267:Dental Prosthesis Design / Q000592:standards; D019094:Dental Prosthesis, Implant-Supported; D006801:Humans; D017755:Prosthesis Fitting; D011786:Quality Control; D019415:Torque
chemical_list: D015921:Dental Implants