Study finds differences in accuracy of intra-oral scanners
SEOUL, South Korea: Even though intra-oral scanners have been around for more than three decades and their use in dental practice is increasing, few investigations have evaluated the 3D accuracy of digital implant scans. As discrepancies between implant components must be minimal, researchers from Seoul National University School of Dentistry have evaluated the trueness of ten intra-oral scanners in determining the positions of simulated implant scan bodies.
The researchers tested the null hypotheses that there would be no significant difference in 3D accuracy among the intra-oral scanners and that the scan body position would have no effect on the trueness.
They evaluated the performance of the CEREC Omnicam and CEREC Primescan (Dentsply Sirona), CS 3600 (Carestream Dental), DWIO (Dental Wings), i500 (Schütz Dental), iTero Element (Align Technology), PlanScan (Planmeca), TRIOS 2 and TRIOS 3 (3Shape), and True Definition (3M) in acquiring the accurate positions of six cylinders simulating implant scan bodies in a partially edentulous model. Digital scans from each intra-oral scanner were compared with the reference data set obtained by means of a coordinate measuring machine. Deviation from the actual positions of the six cylinders along the x, y and z axes and the overall 3D deviation of the digital scan were calculated.
Contrary to the first null hypothesis, the researchers found that the type of intra-oral scanner and the position of the simulated cylindrical scan bodies influenced the degree and direction of the deviations in accuracy. The lowest deviation was found at the cylinder next to the reference origin, while the highest deviation was observed at the contralateral side for all tested scanners. CEREC Primescan and TRIOS 3 had the highest trueness, followed by the i500, TRIOS 2 and the iTero Element—although the difference was not statistically significant. The DWIO and PlanScan showed the lowest accuracy in partially edentulous mandibular digital implant scans.
The second null hypothesis—that scan body position would have no effect on trueness—was also rejected, as digital scans deviated with distance from the reference origin. The further the scan was from the origin, the greater the deviation was. This result is in accordance with previous studies confirming the reduced trueness of digital implant scans owing to accumulation of errors during image stitching.
The research group noted that a limitation of the study was that the digital impressions were collected in an in vitro model, which may differ from in vivo scenarios in which the outcome could be influenced by factors such as patient movement and presence of soft tissue and moisture.
The study authors concluded: “It would be recommended to use an [intra-oral scanner] that is capable of producing accurate complete-arch scans, especially for fabrication of long-span prostheses or appliances.”
The study, titled “Trueness of ten intraoral scanners in determining the positions of simulated implant scan bodies”, was published on 28 January 2021 in Scientific Reports.