In vivo trueness of full-arch implant-supported CAD/CAM restorations and models based on conventional impressions

Objectives: To evaluate a method for in situ reference acquisition of implant positions in complete edentulous maxillae using an industrial scanner. To assess in vivo trueness of full-arch implant-supported fixed dentures (IFD) and dental models based on conventional impressions.Methods: In five subjects, scan-bodies were mounted to six maxillary implants and scanned three times using an industrial scanner (REF). Original impression-based models used to manufacture existing IFDs, (MOD1), and models fabricated from new polyether impressions, (MOD2), were scanned three times with a laboratory scanner. Scan-bodies were aligned and exported with analogue positions corresponding to implant positions. Implant analogues were mounted onto existing IFDs and scanned three times (BRIDGE). CAD files of scan-bodies with inter-aligned CAD-analogues were geometry-aligned to REF. CAD-analogues were aligned to exported files of MOD1 and MOD2, and to BRIDGE. Resulting six CAD-analogues were Globally Aligned using a consistent geometry-based alignment. Deviations were computed after a Reference Point System Alignment at the implant/ prosthetic platform for Cartesian axes and a linear Resultant.Results: REF precision was 9.3 +/- 1 mu m. In vivo trueness for Resultant was MOD1: 36 +/- 16 mu m, MOD2: 28 +/- 7 mu m and BRIDGE: 70 +/- 23 mu m, where MOD1 and MOD2 were statistically significantly different from BRIDGE. In vitro manufacturing trueness of Resultant when MOD1 acted reference for BRIDGE was: 69 +/- 22.Conclusions: This method can be applied for assessing in vivo trueness. CAD/CAM processed IFD showed de-viations twice that of impression-based models, however, errors from impressions and subsequent model scans were not additive to the entire workflow.