Effect of scanning speed, scanning pattern, and tip size on the accuracy of intraoral digital scans

Statement of problem. Currently available intraoral scanning technology makes intraoral scanning quicker and allows the use of smaller scanner tips. However, studies on the influence of scanning speed, tip size, and scanning patterns on scanning accuracy are lacking. Purpose. The purpose of this in vitro study was to evaluate the effect of scanning speed, scanning pattern, and scanner tip size on scanning trueness and precision. Material and methods. A total of 120 complete arch intraoral scans were made with an intraoral scanner (Emerald). The 3 variables were tip size (small and regular), scanning pattern (occlusal first and S-shaped), and scanning speed (slow, regular, and fast). Ten scans for each variable combination were made and exported as standard tessellation language (STL) files. A laboratory scanner (E4) was used for the reference scan. The exported images were analyzed with an image analysis software program (Geomagic Control X). Root-mean-square deviation (RMSD) values between the intraoral scans and the reference scan were calculated to assess trueness. RMSD values between each intraoral scan were calculated to assess precision. Three-way analysis of variance (ANOVA) was used to evaluate the influence of each variable, and Tukey HSD tests were used for multiple comparisons (alpha=.05). Results. For trueness evaluation, tip size was the only significant factor (P<.001). The scans made with a smaller tip showed lower trueness than the scans made with a regular tip. For precision evaluation, all 3 variables, tip size, scanning speed, and scanning pattern, had significant influence (P <=.001). The use of a small tip, fast scanning speed, and S-shaped scanning pattern made intraoral scanning less precise. Conclusions. The use of a small scanner tip negatively affected both trueness and precision. Fast scanning speed and S-shaped scanning pattern produced scans with lower precision than regular or slow scanning speed and the occlusal-first scanning pattern.