Investigations of Intraoral Scan Body Extensions. Effect of Design on the Accuracy, Usability, and Feasibility for...

To evaluate the effect of different scan body extension designs on the accuracy, usability, and feasibility of digital full-arch implant impressions in an edentulous mandibular model. Accuracy was expressed as trueness and precision, usability as scan time, and feasibility as the number of total scan failures.

An edentulous mandibular model with four implants was fabricated with minimal surface morphology. Five scan body extension configurations were tested: no extensions (control), commercially available extensions, conventional impression copings used as extensions, and two morphological 3D-printed extensions oriented between adjacent implants or toward the center of the arch. Two intraoral scanners were used. For each scanner and configuration, 30 scans were acquired. Inter-implant distances were compared against coordinate measuring machine reference values. Trueness was assessed as mean absolute deviation, precision as standard deviation, and differences were analyzed with non-parametric tests.

The highly morphological scan body extensions produced the most consistent improvements. Combined across scanners, trueness improved by 40-57 μm relative to control for the longest inter-implant span. Precision improved significantly for the center-oriented configuration. All scan body extension techniques reduced scan time by 18%-41% and reduced scan failures from 13% (control) to 3% for the morphological designs. Improvements were most pronounced for longer spans and varied between scanners.

Highly morphological 3D-printed scan body extensions significantly improved the accuracy, usability, and feasibility of complete-arch digital implant impressions compared to an unmodified control workflow. Clinical validation is required to confirm these findings for broader use.