Effect of substrate material and abutment geometry on the accuracy of intraoral scanning: An in vitro study.

Statement Of Problem: Digital scanning is gradually replacing conventional impression making, but consensus on how tooth preparation influences the accuracy of intraoral scanning is lacking.

Purpose: The purpose of this in vitro study was to evaluate the effect of substrate material and abutment geometry on the accuracy of digital casts obtained by intraoral scanning.

Material And Methods: The height and total occlusal convergence (TOC) angle were measured in 5 different groups that contained 5 specimens of different materials: natural tooth, cobalt chromium alloy, titanium, zirconium dioxide ceramic, and resin. The specimens were scanned with an industrial scanner to obtain reference data. Each specimen was placed in a maxillary standard dentition model that was assembled in a head simulator. Each dentition model was scanned 10 times with an intraoral scanner (IOS) under operatory lighting conditions to acquire intraoral scanning files for each specimen. All data were imported into a metrology software program and processed. A total of 10 trueness deviations, the mean superimposition results between IOS scanning data and reference data, and precision deviations, the mean superimposition results between IOS scanning data in pairs, were recorded. Two-way analysis of variance (ANOVA) and Tukey multiple comparison test were used to analyze the accuracy of intraoral scanning in relation to the height or TOC angle of the abutment (α=.05). The total means of each substrate material were compared with the Kruskal-Wallis test and Dunn test for multiple comparisons.

Results: The accuracy of scanning images was related to material and abutment geometry (P<.05). Bias was larger as abutment height increased with most substrates. Larger TOC angles increased the accuracy of the digital scans. The trueness deviation of translucent materials and the precision deviation of reflective materials were generally larger.

Conclusions: Substrate material and abutment geometry influence the accuracy of intraoral scanning. The accuracy of IOS generally tended to improve with decreasing height and increasing TOC angle and was affected by different substrates.