title: The effect of impression technique and implant angulation on the impression accuracy of external- and internal-connection implants.
abstract: OBJECTIVE
  The purpose of this in vitro study was to investigate the effect of impression technique and implant angulation on the impression accuracy of external- and internal-connection implants using a novel experimental device.
  
  
  METHODS
  An experimental device was designed and fabricated to make in vitro impressions by means of open- and closed-tray techniques. Impressions of eight implants with two different connections (four external-hex and four internal-hex) at three angulations (0, 15, and 25 degrees) were made using a medium-consistency polyether material. Evaluation of implant impression accuracy was carried out by directly measuring the difference in coordinate values between the implant body/impression coping positioned on the base and the impression coping/laboratory analog positioned in the impression using a touch-probe coordinate measuring machine. Experimental data were analyzed by two-way analysis of variance. The significance level of all hypothesis testing procedures was set at P<.05.
  
  
  RESULTS
  The results showed that: (1) for implants with external connections, impression accuracy is not significantly affected by the impression technique, implant angulation, or their interaction; and (2) for implants with internal connections, impression accuracy is significantly affected only by implant angulation: Impression inaccuracy was greater at the 25-degree implant angulation.
  
  
  CONCLUSIONS
  Within the limitations of this in vitro study, the open- and closed-tray techniques had no effect on the accuracy of multiple implant impressions. The interaction between impression technique and implant angulation was also not significant. However, implant angulation significantly affected the impression accuracy when implants with internal connections were used.
authors.affiliation: Department of Fixed Prosthesis and Implant Prosthodontics, School of Dentistry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Pavlos
authors.initials: P
authors.lastname: Mpikos
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Kafantaris
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Tortopidis
authors.forename: Christos
authors.initials: C
authors.lastname: Galanis
authors.forename: George
authors.initials: G
authors.lastname: Kaisarlis
authors.forename: Petros
authors.initials: P
authors.lastname: Koidis
mesh_terms: D000704:Analysis of Variance; D059605:Dental Implant-Abutment Design / Q000295:instrumentation / Q000379:methods; D015921:Dental Implants; D003760:Dental Impression Materials; D003761:Dental Impression Technique / Q000295:instrumentation / Q000592:standards; D019094:Dental Prosthesis, Implant-Supported; D004867:Equipment Design; D003765:Models, Dental
chemical_list: D015921:Dental Implants; D003760:Dental Impression Materials