Transfer Accuracy of Implant Impressions: Influencing Factors

Objective: The precise transfer of the intraoral implant position to a master cast is a prerequisite for an accurate and passive fit of the prosthetic superstructure and for long-term success. Therefore, the aim of this in-vitro study was to investigate the influence of the implant system, impression material and technique on the transfer accuracy of implant impressions. Methods: An acrylic resin model of the maxilla with a steel base plate was used as a reference. Six implants of two different implant systems (three Xive and three Ankylos implants; Dentsply Friadent) were fixed in the reference model. The pick-up and the reposition impression techniques were used to make 10 impressions with the following materials: Impregum Penta (3M ESPE), Aquasil Monophase (Dentsply DeTrey), P2 Monophase and Flexitime Monophase (both Heraeus Kulzer). Master casts were fabricated with Fuji Rock (GC-Corporation, Tokio, Japan). Measuring abutments were fixed on the implant analogs and the 3D coordinates of each implant position was recorded with a 3D coordinate measuring machine (Rapid CNC, THOME, Germany). Subsequently mean deviation (inclination, overall 3D shift in XYZ direction) was calculated in relation to the reference model. Statistical analysis was performed using ANOVA (α=0.05). Results: The impression technique had a significant influence (p0.05) on the transfer accuracy. The pick-up technique had a significant positive effect on inclination (p0.01). The implants of the Ankylos system showed a higher accuracy with regard to inclination (0.09° ± 0.018°) compared to the Xive implants (-0.15 ± 0.018°). However, the 3D shift was significantly smaller (p0.001) with Xive implants (0.10mm ± 0.06mm) compared to Ankylos implants (0.14mm ± 0.04mm). The impression material had only a minor influence on the transfer accuracy. Conclusions: Under the limits of the study it can be concluded that the pick-up technique produces more accurate casts and should therefore be favoured for daily practice. Keywords: transfer accuracy, impression technique, implant system, impression material