Trueness of Complete-Arch Implant Scans: Influence of Scanning Technique, Intraoral Scanner, and Implant Position (Part I: Linear and Angular Deviations)

<i>Background and Objectives</i>: This study aimed to investigate the effect of the intraoral scanner, scanning technique, and implant position on the trueness measured by linear and angular deviations. <i>Materials and Methods</i>: An edentulous maxillary model with four implants was scanned using four intraoral scanners (Trios 5, Trios 3, Primescan, Medit i700) and four scanning techniques (unmodified, composite, eugenol, dental floss). Each intraoral scanner-scanning technique combination was repeated ten times, producing 160 test datasets. Master reference files were generated with a laboratory scanner. Linear and angular deviations were calculated after superimposing each test scan with its master file. A three-way ANOVA followed by Tukey's HSD test was used to determine statistical differences. Significance was set at <i>p</i> < 0.05. <i>Results</i>: Significant effects of intraoral scanner, scanning technique, and implant position were found for both linear and angular deviations (<i>p</i> < 0.001). Trios 5 showed the highest linear deviation values, although these remained within clinically acceptable limits, while Primescan showed the lowest. Dental floss produced the highest linear and angular deviations, whereas eugenol demonstrated the lowest. Medit i700 demonstrated the lowest angular deviation. <i>Conclusions</i>: All intraoral scanners showed deviations within clinically acceptable thresholds, although Trios 5 showed the highest linear deviation. Among scanning techniques, dental floss resulted in the highest linear and angular deviations. Deviations were lower between adjacent implants and higher across 1-3, 1-4, and 2-4.