Accuracy of digital impressions of multiple dental implants: an invitro study.

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Studies demonstrated that the accuracy of intra-oral scanners can be compared with conventional impressions for most indications. However, little is known about their applicability to take impressions of multiple implants. The aim of this study was to evaluate the accuracy of four intra-oral scanners when applied for implant impressions in the edentulous jaw. An acrylic mandibular cast containing six external connection implants (region 36, 34, 32, 42, 44 and 46) with PEEK scanbodies was scanned using four intra-oral scanners: the Lava C.O.S. and the 3M True Definition, Cerec Omnicam and 3Shape Trios. Each model was scanned 10 times with every intra-oral scanner. As a reference, a highly accurate laboratory scanner (104i, Imetric, Courgenay, Switzerland) was used. The scans were imported into metrology software (Geomagic Qualify 12) for analyses. Accuracy was measured in terms of trueness (comparing test and reference) and precision (determining the deviation between different test scans). Mann-Whitney U-test and Wilcoxon signed rank test were used to detect statistically significant differences in trueness and precision respectively. The mean trueness was 0.112mm for Lava COS, 0.035mm for 3M TrueDef, 0.028mm for Trios and 0.061mm for Cerec Omnicam. There was no statistically significant difference between 3M TrueDef and Trios (P=0.262). Cerec Omnicam was less accurate than 3M TrueDef (P=0.013) and Trios (P=0.005), but more accurate compared to Lava COS (P=0.007). Lava COS was also less accurate compared to 3M TrueDef (P=0.005) and Trios (P=0.005). The mean precision was 0.066mm for Lava COS, 0.030mm for 3M TrueDef, 0.033mm for Trios and 0.059mm for Cerec Omnicam. There was no statistically significant difference between 3M TrueDef and Trios (P=0.119). Cerec Omnicam was less accurate compared to 3M TrueDef (P<0.001) and Trios (P<0.001), but no difference was found with Lava COS (P=0.169). Lava COS was also less accurate compared to 3M TrueDef (P<0.001) and Trios (P<0.001). Based on the findings of this invitro study, the 3M True Definition and Trios scanner demonstrated the highest accuracy. The Lava COS was found not suitable for taking implant impressions for a cross-arch bridge in the edentulous jaw.