Accuracy of traditional open-tray impression, stereophotogrammetry, and intraoral scanning with prefabricated aids for implant-supported complete arch prostheses with different implant distributions: An in vitro study

Statement of problem. Conventional impression techniques for complete arch implant-supported fixed dental prostheses (CIFDPs) are technique sensitive. Stereophotogrammetry (SPG) and intraoral scanning (IOS) may offer alternatives to conventional impression making. Purpose. The purpose of this in vitro study was to assess the accuracy and passive fit of IOS with prefabricated aids, SPG, and open tray impression (OI) for CIFDPs with different implant distributions. Material and methods. Three definitive casts with 4 parallel implants (4-PARA), 4 inclined implants (4-INCL), and 6 parallel implants (6-PARA) were fabricated. Three recording techniques were tested: IOS with prefabricated aids, SPG, and OI. The best and the worst scans were selected to fabricate 18 milled aluminum alloy frameworks. The trueness and precision of distance deviation (triangle td and triangle pd), angular deviation (triangle t theta and triangle p theta), root mean square errors (triangle tRMS for triangle pRMS), and passive fit score of frameworks were recorded. Two-way ANOVA was applied. Results. SPG showed the best trueness and precision (95%CI of triangle td/t theta/triangle tRMS, 31 to 39 mu m, 0.22 to 0.28 degrees, 20 to 23 mu m; 95%CI of triangle pd/p theta/triangle pRMS, 9 to 11 mu m, 0.06 to 0.08 degrees, 8 to 10 mu m), followed by OI (61 to 83 mu m, 0.33 to 0.48 degrees, 28 to 48 mu m; 66 to 81 mu m, 0.29 to 0.38 degrees, 32 to 41 mu m) and IOS (143 to 193 mu m, 0.37 to 0.50 degrees, 81 to 96 mu m; 89 to 111 mu m, 0.27 to 0.31 degrees, 51 to 62 mu m). Tilted implants were associated with increased distance deviation. Increased implant number was associated with improved recording precision. The passive fit of frameworks was negatively correlated with the RMS error, and the correlation coefficient was -0.65 (P=.003). Conclusions. SPG had the best accuracy. Implant distributions affected implant precision. The RMS error can be used to evaluate the passive fit of frameworks.