Comparison of an indirect impression scanning system and two direct intraoral scanning systems in vivo

This in vivo study aimed to compare the marginal discrepancies of zirconia copings manufactured on the basis of two direct intraoral scanning systems and the indirect digitization of a conventional impression.

A total of 63 teeth in 23 patients were prepared to receive full-coverage crowns. Subsequently, these teeth were intraorally scanned using CEREC AC Omnicam and Cara TRIOS and a conventional impression was taken with the scannable PVS Flexitime Fast & Scan. The conventional impression was then extraorally digitized using a D700 laboratory scanner. The zirconia copings were manufactured on the basis of the resulting datasets. Silicone replicas of the copings were produced and sectioned for the measurement of the marginal discrepancy under a digital microscope.

The statistical analysis showed no significant differences between the two intraoral scanners, the CEREC AC Omnicam (86.09 μm ± 61.46 μm) and the Cara TRIOS (88.95 μm ± 54.46 μm). However, the discrepancies of the zirconia copings obtained from the laboratory scans of conventional impressions (143.29 μm ± 100.71 μm) showed significant differences. Both intraoral scanners achieved a marginal discrepancy below 100 μm, whereas the laboratory scan exhibited considerably higher values.

The intraoral scanners tested allow for the production of single-tooth-restorations with an adequate marginal fit, whereas the production of restorations on the basis of the scan of a conventional impression led to vast marginal gaps.

The method of digitizing a conventional impression using a laboratory scanner seemed to have reached its limits in the clinical environment.