Influence of the scanning path on the accuracy of intraoral scanners in the implanted edentulous patient: an in vitro study

Aim: The aim of the present in vitro study was to investigate the influence of scan paths on the accuracy (trueness and precision) of intraoral scanning of an implant impression on an edentulous patient.
Materials and methods: An epoxy resin maxillary cast was made with six bone level implants (NobelParallel Conical Connection RP). The implants were placed at the sites of the central incisors, canines, and first molars. The transgingival component (multi-unit) was screwed onto the implants. The scanbodies (Elos Accurate IO 2C-A) were then screwed onto the multi-units. The cast was run through a coordinate measurement machine to obtain a control model. Then, five different scanning paths were applied by a single operator: the zigzag technique (ZZT); the zigzag technique with palatal (ZZTP); the wrap technique (WT); the wrap technique with palatal (WTP); and the big zigzag technique (BZZT). Finally, each scan was compared with the control model. Results were assessed by one-way ANOVA and linear mixed effects models with a significance level of P 0.05.
Results: The results showed that scan paths ZZT and ZZTP had significantly lower absolute positioning errors and root mean square errors than the other techniques (P 0.0001). For distances between consecutive implant axes and for absolute vertical errors, their superiority was borderline (P 0.10). Overall, techniques ZZT and ZZTP were equally performant and proved to be the most accurate scan paths.
Conclusions: The present in vitro experimental study demonstrates that the scan path can have an influence on the accuracy of the optical impression for full-arch rehabilitations on implants.