Impact of a novel tooth-shaped auxiliary device on the scanning accuracy of complete-arch implant impressions

This in vitro study aimed to evaluate the impact of a novel Tooth-Shaped Auxiliary Device (TSAD) on the scanning accuracy (trueness and precision) of complete-arch implant impressions, in comparison to conventional splinted impressions (CI) and standard intraoral scans (IOS). A mandibular edentulous master model with six implants was used as the reference. Three impression methods were tested ( n = 10 per group): CI, IOS, and IOS with the TSAD. The TSAD, featuring a biomimetic occlusal geometry, was digitally designed and 3D-printed to attach to scan bodies. Scans were performed using a 3Shape TRIOS 3 scanner across three implant configurations (BCDE, BCDEF, and ABCDEF). The resulting Standard Tessellation Language (STL) files and the reference scan were used to calculate trueness and precision using best-fit alignment and mean linear deviation between implants. Statistical analysis was performed using two-way ANOVA with Bonferroni correction for post-hoc comparisons, and simple effects analyses for significant interactions. The effect of TSAD on scanning accuracy varied by implant configuration. In the BCDE and BCDEF configurations, no statistically significant differences in trueness or precision were observed between TSAD and CI (trueness: P = 1.000 and P = 0.883; precision: P = 0.662 and P = 0.368, respectively). In the ABCDEF configuration, TSAD demonstrated significantly better trueness and precision than both CI and IOS (all P < 0.001 for trueness; precision: P = 0.024 vs. CI, P = 0.003 vs. IOS). The precision of TSAD remained stable across the three implant configurations ( P = 0.435), whereas the trueness and precision of IOS varied significantly across configurations (both P < 0.001). Under in vitro conditions, TSAD demonstrated accuracy similar to CI in partial-arch configurations and significantly better accuracy than both CI and IOS in the full-arch configuration. Further studies are needed to validate its performance under clinical conditions.