Accuracy of New-Generation Intraoral Scanners in Digitizing All-on-Four Implant Models with Varying Posterior Implant Angulations: An In Vitro Trueness and Precision Evaluation

Background: The increasing adoption of digital workflows in implant dentistry necessitates rigorous assessment of intraoral scanning, particularly for complex full-arch rehabilitations like All-on-Four prostheses, where posterior implant angulation may impact the accuracy of optical data acquisition. Objectives: This in vitro study aimed to assess the accuracy of digital intraoral scanners in scanning All-on-Four implant models with different posterior implant angulations. Methods: Two epoxy resin All-on-Four implant models were fabricated with two posterior implant angulations (30-degree and 45-degree). Both models were digitized to obtain control datasets using a Smart Optics reference scanner (REF). Four intraoral scanners were comparatively assessed: Cerec Omnicam AC (OMN), Trios 4 (TRI), Cerec Primescan AC (PRI), and Medit i700 (MED), with nine scans per each scanner (n = 9). All STL files were exported and analyzed using Geomagic Control X with root mean square (RMS) values computed for trueness and precision assessments. Results: The comparison between IOS types in terms of trueness revealed that with 30° angulation, the MED group showed the statistically significant least deviation (p = 402). With 45° angulation, both PRI and OMN scanners showed the statistically significant highest deviation values (p = 0.047 and 0.007, respectively). MED again showed the statistically significant least deviation (p = 402). For precision evaluation in 30° angulation models, PRI and OMN scanners showed the statistically significant least deviation values (p = 402 and <0.001, respectively). While, in 45° angulation models, no statistically significant inter-scanner differences were observed. Conclusions: While MED, PRI, and OMN scanners demonstrated clinical validity for 30° angled posterior implants, only the MED system achieved sufficient accuracy for 45° tilt. These findings emphasize the critical relationship between scanner selection and extreme implant angulations in full-arch digital workflows.