Comparison of impression techniques used to obtain digital models for CAD/CAM post and core

The objective of this study was to compare the accuracy of 2 root canal impression techniques used to obtain digital models for post and core restorations in a computer-aided design/computer-aided manufacturing process. Cone beam computed tomography and segmentation software were used to calculate the post space (PS) volume of a decoronated, endodontically treated bovine tooth. Measurements were performed 10 times to obtain a mean reference value that served as the control. A benchtop dental scanner was used to scan 10 impressions made with polyvinyl siloxane (PVS) and 10 made with chemically activated acrylic resin (CAAR) to obtain 3-dimensional digital models, whose volumes were measured with mesh processing software. The 1-sample t test was used to compare the mean volume of each test impression group with the control PS volume (trueness), and the t test for independent samples was used to compare the test groups with each other (precision). The dispersion, variance, and standard deviation were analyzed (α = 0.05). The mean (SD) control PS volume was 84.11 (0.15) mm³, while the volume of the CAAR group was 78.70 (2.33) mm³, and the volume of the PVS group was 86.20 (2.08) mm³. The difference between the PS volume and the volume of each test group was statistically significant (CAAR, P < 0.001; PVS, P = 0.011), and the volumes of the test groups were significantly different from each other (P < 0.001). The variance was 5.42 mm³ in the CAAR group and 4.32 mm³ in the PVS group. While both materials showed some distortion, the results suggest that the PVS technique generates more accurate digital models than the CAAR technique, with values that more closely approach the reference PS volume and exhibit less variation in successive measurements.