The accuracy of stereophotogrammetric, intraoral scanning, and conventional open-tray impression techniques for complete arch fixed implant-supported prostheses: An in vitro study

This study compares the accuracy (trueness and precision) of stereophotogrammetric (SPG), intraoral scanning (IOS), and conventional (CI) techniques for complete-arch fixed implant-supported prostheses with three different distal implant angulations. Three edentulous mandibular acrylic master casts were fabricated. Four dental implants were placed on each casts, two at the lateral incisor areas and two at the second premolar areas. Casts varied in the angulations of the two distal implants: Model 1, four straight multi-unit abutments (MUAs); Model 2, two straight and two 17° angled MUAs; and Model 3, two straight and two 30° angled MUAs . Three impression techniques were compared: splinted open-tray CI using vinyl polysiloxane (light body and putty), IOS, and SPG. Each impression technique was performed five times resulting in standard tessellation language (STL) files. The superimposition process was performed by aligning reference and test files via best-fit algorithms. Trueness and precision were evaluated by calculating root mean square (RMS) three-dimensional (3D) deviation and cumulative angular deviation of CI, IOS and SPG impression techniques. For trueness, CI demonstrated significantly higher 3D deviation than IOS and SPG across all models (p < 0.001) . CI, Model 1 exhibited significantly lower 3D deviation compared to Model 2 (p < 0.01) and Model 3 (p < 0.001). Additionally, CI showed greater cumulative angular deviation in Model 1 compared to IOS (p = 0.04) . For precision, no significant differences were found in the 3D deviation and cumulative angular deviation among the models and techniques. For Trueness, the CI technique exhibited greater 3D deviation than IOS and SPG across all models (p < 0.001) . Precision showed no significant differences among techniques. These findings indicate that IOS and SPG demonstrate superior accuracy to CI across all models. The accuracy of implant impressions is crucial for ensuring a passive fit in complete-arch implant-supported prostheses. This in vitro study demonstrates that the IOS and SPG techniques provide higher trueness compared to the splinted open-tray CI technique, particularly in cases involving angled MUAs. These findings reinforce the reliability of digital scanning techniques as viable alternatives to the CI technique for implant impressions, offering improved accuracy.