The reference mesh matters: a role in defining accuracy of intraoral scanners

Objectives: This in vitro study aimed to evaluate how the choice of reference mesh influences the assessment of trueness for IOS devices. Methods: Four IOSs (Primescan, IS 3800, Trios 3, and i600) were used to scan a typodont maxillary cast with a prepared right first molar for endocrown restoration (n = 10 per scanner). Two distinct reference meshes were employed: a laboratory dental scanner (RC1) and a metrological-grade scanner (RC2). Experimental and reference meshes were superimposed using metrology software (Geomagic Control X) to calculate root mean square (RMS) deviations, which were used to assess trueness. Data were analyzed using two-way ANOVA and Tukey's post hoc test (α = 0.05). Results: Trueness varied significantly according to the reference mesh and the preparation region. Significantly lower trueness at the marginal region was observed across all scanners when RC2 was compared with RC1. Additionally, greater discrepancies were observed in the pulpal region for RC2 in Primescan, IS 3800, and i600 (P < 0.0001). Conclusions: The selection of the scanner for obtaining the reference mesh substantially influences the trueness assessment of IOSs. Consequently, IOS performance may be misrepresented if the reference mesh characteristics are not considered. Standardized protocols for reference meshes are essential for reliable and comparable digital dentistry studies. Clinical significance: The selection of reference scanners may affect the true outcomes of intraoral scanner accuracy assessments. Selection of scans obtained with adequate parameters and standardized reference protocols are essential to enhance the reliability of trueness and precision assessments, thereby improving the predictability and clinical outcomes of digitally fabricated restorations.