Evaluation of the Milling Accuracy of Zirconia-Reinforced Lithium Silicate Crowns Fabricated Using the Dental Medical Device System: A Three-Dimensional Analysis

This study aimed to analyze the milling accuracy of lithium disilicate and zirconia-reinforced silicate crown fabricated using chairside computer-aided design/manufacturing (CAD/CAM) system. Mandibular left first premolar was selected for abutment. A master model was obtained for digital impression using an intraoral scanner, and crowns were designed using a CAD software design program. Amber Mill (AM), IPS e max CAD (IPS), and CELTRA DUO (CEL) were used in the CAD/CAM system, and a total 45 crowns (15 crowns each for AM, IPS, and CEL) was fabricated. Milling accuracy was analyzed with respect to trueness, measured by superimposing CAD design data and scan data through a three-dimensional program to compare the outer and inner surfaces and internal and external parts, thereby acquiring both quantitative and qualitative data. Data were analyzed using the non-parametric test and Kruskal-Wallis H test. In addition, the Mann-Whitney U test was used by applying the level of significance (0.05/3 = 0.016) adjusted by post-analysis Bonferroni correction. All the measured parts of the lithium disilicate and zirconia-reinforced silicate crowns showed statistically significant differences (p < 0.05). The lithium disilicate (AM and IPS) materials showed superior milling accuracy than the zirconia-reinforced lithium silicate (CEL) materials.