Purpose: The aim of this study was to investigate the effect of implant subgingival depth on the trueness and precision of the 3D implant position, and the effect of digital implant impression techniques on the 3D implant position.

Materials and methods: Three resin master models were created with implant analogs submerged 3, 6, and 9 mm from the gingival margin. Four intraoral scanners (TRIOS, DWIO, Omnicam, and TruDef), one laboratory scanner (E3), and a conventional impression technique were used to take impressions of the master models, which resulted in six test models for each depth. These six impression techniques were performed six times for precision assessment. The master models were sent for high-powered micro-focused computed tomography as the gold standard control group. The scan body positions of the test models and their control models were superimposed using reverse-engineering software. The 3D distortion of the implant position in each comparison was measured by linear distortion (dx, dy, dz) and calculated as the global linear distortion (dR).

Results: The trueness of the mean dR values at the 3-mm, 6-mm, and 9-mm implant depths was 99 μm, 60.6 μm, and 107 μm, respectively. The least significant difference test of the impression system showed that all the digital impression techniques except the DWIO scanner had better trueness than the conventional impression technique. The 6-mm implant depth exhibited a significantly lower 3D distortion of the implant position than those of the 3-mm and 9-mm implant depths. The E3 scanner had the highest precision, while the conventional impression technique had the lowest precision. All the intraoral scanners except the DWIO scanner showed better precision than the conventional impression technique.

Conclusion: Most of the intraoral scanners had better trueness and precision than the conventional impression technique for up to 6 mm of implant subgingival depth.