Evaluation of Passivity of Co-Cr Complete Arch Screw Retained Maxillary Prostheses Using Different Intraoral Scanners With the Aid of Auxiliary Geometric Device

To evaluate the influence of an auxiliary geometric device (AGD) on the accuracy of complete-arch digital scans in edentulous patients by measuring the passivity of fit of 3D-printed frameworks.

In this in vivo study, 7 patients were selected to receive complete arch screw-retained prostheses supported by 4 implants. Five data acquisition methods were compared: extraoral scanning of open-tray impressions (EO), intraoral scanning using Medit i600 (M) or CEREC Primescan (P), and intraoral scanning with an auxiliary geometric device using Medit (MAGD) and Primescan (PAGD). Reference models were generated using intraoral photogrammetry to assess passivity. Cobalt-Chromium frameworks were 3D printed for each group. Passivity was assessed using a modified one-screw test to measure marginal gaps (μm) by using digital imaging (in vitro) and radiographic analysis (in vivo). Data were analyzed using One-way ANOVA followed by Tukey's post-hoc tests. (α=.05 for all tests).

Significant inter-group differences were found (P=.001). Microscopic analysis showed the lowest marginal gap in the EO group (25.07±7.77 μm), followed by PAGD (33.58±5.63 μm), and MAGD (50.34±13.71 μm). Groups P (60.91±13.41 μm) and M (71.84±12.44 μm) exhibited the largest gaps and were not significantly different (P>.05). Radiographic findings were similar to microscopic. However, EO (56.92±16.62 μm) and PAGD (68.68±18.91 μm) groups were statistically comparable (P>.05).

The use of an auxiliary geometric device significantly improved the accuracy of digital scans for edentulous arches. Intraoral scanner, Primescan combined with a geometric device achieved passivity levels comparable to conventional splinted impressions.