Influence of arch form on the accuracy of digital workflow in all-on-four implant rehabilitation cases (an in vitro study)

BACKGROUND: Variations in arch form may influence the accuracy of digital impressions for implant-retained fixed dental prostheses. Differences in arch width, curvature, and span length can affect scanning continuity and data stitching, potentially impacting trueness and precision during full-arch acquisition. However, the extent to which arch form and scanning strategy interact to influence digital impression accuracy remains unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of arch form on the accuracy of the digital work flow of implant-retained fixed dental prostheses. METHODS: Three maxillary edentulous full-arch models with different forms-ovoid (O), tapered (T), and square (S)-were 3D printed. Four implants were placed in each model and loaded with scan bodies. Reference scans were obtained using a high-precision laboratory scanner. Each model was scanned with a Medit i700 intraoral scanner (IOS) using three scanning strategies Linear (L), S-curve (S), and Wave (W). Each strategy was performed 10 times per model, generating 90 STL files. Trueness and precision were evaluated using Geomagic Control X software and statistically analyzed (α = 0.05). RESULTS: Arch form significantly influenced trueness (p < 0.001), with the tapered arch demonstrating the highest trueness, followed by square and ovoid forms. Precision was significantly affected by arch form (p < 0.001) and scanning strategy (p = 0.006). The wave strategy showed significantly greater precision than the other strategies. No significant interaction was found between arch form and scanning strategy (p = 0.769). CONCLUSION: Within the limitations of this in vitro study, Arch morphology and scanning strategy significantly impact both the trueness and precision of full-arch implant scans. While tapered arches demonstrated statistically highest trueness and precision and the wave scanning strategy maximized precision, all tested combinations remained safely within the clinically acceptable threshold for passive prosthetic fit.