Background <p>There is a lack of comprehensive comparative data assessing the accuracy of multiple intraoral scanners (IOSs) across both partially and completely edentulous cases, particularly in the presence of variable implant positions. The aim of this study was to assess the effect of IOSs and implant positions in 4-unit and All-on-4 restorations on the trueness and precision of digital impressions.</p> Methods <p>Two maxillary resin models were fabricated: a partially edentulous arch planned for a 4-unit fixed dental prosthesis (FDP) with implants at the canine and first molar sites, and a completely edentulous arch for an All-on-4 FDP. Each model was scanned (<i>n</i> = 10 each) using five IOSs: Omnicam AF, CS 3800, Trios 3&#xa0;A, Medit i500, and Primescan AC. Scan data were analyzed using Geomagic Control X to assess trueness and precision. Statistical analysis was performed using three-way ANOVA, followed by two-way ANOVA and post hoc testing (<i>p</i> &lt; 0.05).</p> Results <p>Regarding trueness in the 4-unit FDP group, CS3800 exhibited the highest RMS in anterior and posterior implants. In the All-on-4 group, Trios and Medit i500 showed the lowest RMS in anterior implants, and Medit i500 showed the lowest RMS in posterior implants. CS3800 showed the highest RMS in both the implant positions. Regarding precision in the 4-unit FDP group, Trios and Primescan achieved the lowest RMS. CS3800 and Medit i500 showed the highest RMS in posterior implants. In All-on-4, Omnicam showed the least RMS in anterior implants, while Primescan the least in posterior implants. All scanners showed less precision in posterior implants in both models.</p> Conclusions <p>Under controlled in vitro conditions, differences in trueness and precision were observed among intraoral scanners, depending on implant position and restoration type. In All-on-4 restorations, Medit i500 showed the highest trueness. Whereas, in 4-unit FDPs, Trios 3 and Primescan exhibited the highest precision. Anterior and posterior implant positions exhibited varying levels of trueness and precision deviation across scanners.</p> Clinical significance <p>Intraoral scanner accuracy is influenced by implant position and prosthesis configuration, with posterior implant positions generally exhibiting reduced precision under in vitro conditions. These findings represent statistically significant differences observed within an experimental model and do not establish scanner ranking, clinical acceptability thresholds, or in vivo scanner suitability.</p> Graphical Abstract <p></p>