Purpose: The aim was to evaluate the trueness and precision of four different intraoral scanners for scanning endocrown preparations with two depths (4 mm and 6 mm).

Materials and methods: Tooth preparation for an endocrown was done and scans were divided according to depth of the preparation. The tooth scans were divided into 2 groups, Group A an endocrown with 6 mm depth and a butt joint margin of 2 mm thickness all around, Group B an endocrown with 4 mm depth, then each group was divided into 4 subgroups according to the intraoral scanner used for scanning, Omnicam v. 4.4.4, Omnicam v.4.4.6, Medit i500, 3Shape Trios 3 respectively, Reference scan were obtained from InEoS X5 extraoral scanner, and 10 test scans of each cavity were made with 4 IOSs. The STL files obtained were compared to reference models (trueness) and within each test group (precision) using a 3D analysis software program (Geomagic Control X). Obtained data were analyzed with three-way ANOVA.
Results. Regarding trueness, Three-way ANOVA revealed significant differences between the different types of scanners (p < 0.001) (Omnicam 4.4.4: 56.53 ± 6.08 Omnicam 4.6.2: 47.68 ± 12.11 Medit i500: 52.07 ± 8.92 Trios 3: 38.81 ± 8.72). Preparation depth showed significant influence on the trueness (p < 0.001) (6 mm depth 55.70 ± 8.22, 4 mm depth 41.84 ± 9.46). For precision three-way ANOVA revealed significant differences between the different types of scanners (p < 0.001). Preparation depth also had significant influence on the precision (p < 0.001).