Influence of Different Intraoral-scan-bodies on the Implant Transfer Accuracy

Objectives: Numerous studies demonstrated that different factors may influence the accuracy of intraoral scans (ISc). The scanning path, the software version, a lack of calibration, different users and the intraoral scanner (IOS) itself were identified as potentially influential. However, studies of the influence of intraoral scan bodies (ISBs) on the transfer accuracy are rare. Therefore, the present study investigated the transfer accuracy (trueness and precision) of three different ISBs using an intraoral scanner compared with a conventional impression.

Methods: A model of a partially edentulous upper jaw with a reference cube served as an implant master model (IMM) simulating a patient situation. The model was digitized using X-ray computed tomography to determine the implant-abutment-interface-points (IAIPs). Three different ISBs (nt-trading(NT)/Kulzer(KU)/Medentika(MED)) were investigated. Digital impressions were taken using a Trios-3 IOS (3Shape; n=10), conventional implant impressions were taken for comparison (Impregum; n=10). The conventional models were digitized and all models (digital and conventional) were superimposed using a coordinate system with the reference file to determine the three-dimensional deviations in between the IAIPs. Results for the accuracy were analyzed using a two-factorial mixed ANOVA (SPSS-25).
Results: The deviations in between the IAIPs ranged from 11±4 μm (conventional) to 17±4 μm (NT). Pairwise comparisons showed significant differences between all digital and conventional impression series. With the conventional impressions, the accuracy were not affected to the respective implant positions. However, there were significant differences in between the individual positions of the implants in the digital impressions. Longer scanning paths resulted in higher deviations of the implant positions in digital impressions.
Conclusions: Overall, all ISBs examined are suitable for the transfer of implant position onto the digital model. If the scanning path remains within a quadrant, digital and conventional techniques showed comparable transfer accuracy.