Accuracy of two best-fit alignment strategies with different reference areas for wear measurement with an intraoral scanner: An in vitro study.

Abstract

The aim of this in vitro study was to assess and compare the accuracy of 2 best-fit alignment strategies with different reference areas for wear measurement with an intraoral scanner. 8 anatomic-contour zirconia crowns were fabricated and scanned twice with an intraoral scanner. One of the scan data (Data Trueness) was duplicated and wear facets were simulated (Data Wear). The other scan data (Data Baseline) was aligned to Data Wear by 2 best-fit alignment strategies with different reference areas (the occlusal surface with no signs of wear and the axial surface), and 3D deviation analysis was performed to detect the wear loss. The 3D deviation between Data Trueness and Data Wear was calculated as the truth-value for accuracy evaluation. Color-difference map showed Group Occlusal had a similar wear-facet distribution to Group Trueness, while Group Axial showed an obvious tilting position and the obtained height loss values were larger and with large standard deviations. Both Group Occlusal and Group Axial showed significant differences from Group Trueness in maximum height loss and mean height loss(P<.05), while no significant difference in mean distance(P>.05). Paired t test showed significant differences between Group Occlusal and Group Axial in maximum height loss and mean height loss(P<.05), while no significant difference in mean distance (P>.05). Best-fit alignment with the occlusal reference area produces a better alignment result than that with the axial reference area. Wear measurement with an intraoral scanner is potential but prone to overestimate the height loss.