(1) Background: This systematic review intends to answer the following Patient–Intervention–Comparison–Outcome (PICO) question: Do digital impression systems generate significant errors during scanning in extensive implant restorative treatments? (2) Methods: Following the PRISMA protocol and according to predefined inclusion criteria, two trained investigators searched for relevant articles in the PubMed database and related sources using a standard keyword sequence. The investigators were responsible for selecting studies and performing quality analysis. (3) Results: From 78 titles, only 9 studies were selected. An analysis of registration distortion variations was conducted for each potential influencing factor in terms of accuracy: interimplant distance, implant angulation, scanner type, and scanning body type. The results showed repeatable differences in accuracy between types of scanning technologies and techniques, and a positive correlation between interimplant distance and the amplitude of deviations detected in comparative analysis, with the highest error levels in total edentulous arch recording. There was no consensus on the error level owing to implant angulation, and statistically significant differences were found between the types of scan bodies used. (4) Conclusions: Digital impression systems generate significant errors during scanning in extensive implant restorative treatments, influenced by scanning technology, interimplant distance, and scanning body type.