Endocrown and intraoral scanning: a segmented analysis of mesh trueness from six scanners

To evaluate the trueness of digital scans of endocrown preparations with different preparation designs and across different preparation areas, using six different devices. Secondarily, to evaluate the mesh vertex density-trueness relationship.

Two teeth from a maxillary typodont were prepared for endocrown with and without ferrule. Then, reference scans from each tooth were obtained by an industrial scanner. Experimental meshes were captured by the same operator with six different intraoral scanners (n = 10) following a standardized scanning pattern. The reference meshes were segmented into areas (margin, axials, and pulpal walls) and compared with the experimental meshes by using Geomagic Control X software. A descriptive analysis of the mesh data was also conducted (Meshmixer). Trueness (root mean square values) was evaluated using two-way ANOVA with Tukey's post hoc test. Spearman correlation was applied to explore the relationship between vertex density and RMS. The significance level was set at α = 0.05.

Trueness of digital scans varied according to the presence of a ferrule and the region of preparation. The margin in the preparation with ferrule was the region with lowest trueness compared to non-ferrule preparations across all scanners (p < 0.0001). This difference was not observed in the internal walls, which showed the lowest discrepancies overall (0.013-0.025 mm). Digital scans of the pulpal wall from Primescan, IS 3700, and TRIOS 3 had discrepancy values close to the internal walls. In contrast, Omnicam, Dexis 3800, and Medit showed greater discrepancy at the pulpal wall in ferrule preparations. No correlation was observed between vertex density and trueness.

Trueness of digital scans is reduced at the margin of endocrown preparation with ferrule compared to non-ferrule preparation. Internal walls had the lowest discrepancies, with minimal variation across preparation types and regions. Pulpal wall trueness varied depending on the scanner. Vertex density did not correlate with trueness.

The preparation design strongly influences the trueness of intraoral scanners. Clinicians should recognize that such preparation design inherently reduces trueness and adjust scanning parameters accordingly. Moreover, mesh density solely is not a reliable indicator of scanning trueness in the topography evaluated.