Precision and Accuracy of a Digital Impression Scanner in Full-Arch Implant Rehabilitation

To evaluate the accuracy and precision of a digital scanner used to scan four implants positioned according to an immediate loading implant protocol and to assess the accuracy of an aluminum framework fabricated from a digital impression.

Five master casts reproducing different edentulous maxillae with four tilted implants were used. Four scan bodies were screwed onto the low-profile abutments, and a digital intraoral scanner was used to perform five digital impressions of each master cast. To assess trueness, a metal framework of the best digital impression was produced with computer-aided design/computer-assisted manufacture (CAD/CAM) technology and passive fit was assessed with the Sheffield test. Gaps between the frameworks and the implant analogs were measured with a stereomicroscope. To assess precision, three-dimensional (3D) point cloud processing software was used to measure the deviations between the five digital impressions of each cast by producing a color map. The deviation values were grouped in three classes, and differences were assessed between class 2 (representing lower discrepancies) and the assembled classes 1 and 3 (representing the higher negative and positive discrepancies, respectively).

The frameworks showed a mean gap of < 30 μm (range: 2 to 47 μm). A statistically significant difference was found between the two groups by the 3D point cloud software, with higher frequencies of points in class 2 than in grouped classes 1 and 3 (P < .001).

Within the limits of this in vitro study, it appears that a digital impression may represent a reliable method for fabricating full-arch implant frameworks with good passive fit when tilted implants are present.