Comparative reproducibility analysis of 6 intraoral scanners used on complex intracoronal preparations

Although studies have reported the trueness and precision of intraoral scanners (IOSs), studies addressing the accuracy of IOSs in reproducing inlay preparations are lacking.

The purpose of this in vitro study was to compare the accuracy of representative IOSs in obtaining digital scans of inlay preparations and to evaluate whether the IOSs had sufficient depth of field to obtain accurate images of narrow and deep cavity preparations.

Digital scans of a bimaxillary typodont with cavity preparations for inlay restorations on the maxillary first premolar, first and second molar, mandibular second premolar, and first molar were obtained using 6 IOSs (CEREC Omnicam, E4D, FastScan, iTero, TRIOS, and Zfx IntraScan). Standard tessellation language (STL) data sets were analyzed using the 3-dimensional analysis software (Geomagic Verify). Color-coded maps were used to compare the magnitude and pattern of general deviation of the IOSs with those of a reference scan. Each tooth prepared for inlay restoration was digitally cut out, and the trueness and precision of each IOS were measured using the superimposition technique. Statistical analyses were conducted using statistical software (α=.05).

The trueness values were lowest with the FastScan (22.1 μm), followed by TRIOS (22.7 μm), CEREC Omnicam (23.2 μm), iTero (26.8 μm), Zfx IntraScan (36.4 μm), and E4D (46.2 μm). In general, the digital scans of more complicated cavity design showed more deviation. Color-coded maps showed positive vertical discrepancy with the E4D and negative vertical discrepancy with the Zfx IntraScan, especially on the cavity floor. Regarding precision, the highest value was observed in the E4D (37.7 μm), while the lowest value was observed with the TRIOS (7.0 μm). However, no significant difference was found between teeth with different inlay preparations. Scanning errors were more frequently seen in the cervical area.

Different IOSs and types of cavity design influenced the accuracy of the digital scans. Scans of more complex cavity geometry generally showed higher deviation. The E4D exhibited the most deviation in both trueness and precision, followed by the Zfx IntraScan. The E4D and Zfx IntraScan appeared to have less depth of field than the others to obtain digital scans for inlay preparation with different heights.