Trueness of Intraoral Scanners for Edentulous Mandibular Arches With and Without Landmarks

The purpose of this in vitro study was to evaluate the trueness of three intraoral scanners (IOS) and to assess the impact of geometrical landmarks on the digitization of edentulous mandibular complete-arch casts using a standardized scanning protocol.

A 3D-printed edentulous mandibular cast with five cylindrical landmarks was scanned using three IOS systems (Medit i700, Primescan AC and Trios 5) under two conditions: with and without geometrical landmarks (GL/NG). Each scanner performed 15 scans per condition. A coordinate measuring machine (CMM) provided reference values for cross-arch and inter-cylindrical distances. STL files were analyzed in GOM Inspect to calculate trueness and precision. Statistical evaluation included Shapiro-Wilk tests and paired t-tests ( = 0.05).

Only the Medit i700 scanner showed significantly improved trueness with geometrical landmarks for both cross-arch (P = 0.0011) and inter-cylindrical (P = 0.0060) measurements. Primescan AC and Trios 5 scanners showed no significant differences between GL and NG conditions (P > 0.05). Visual analyses supported these findings, with Medit i700 benefiting from landmarks, while Primescan AC and Trios 5 maintained high trueness regardless of scanning strategy.

The addition of geometrical landmarks improved scan trueness significantly for the Medit i700 scanner but had no measurable effect on Primescan AC or Trios 5. These findings suggest that the influence of auxiliary landmarks is scanner-dependent and should be considered when optimizing scanning protocols for edentulous arches.