The marginal and internal discrepancy of zirconia coping milled by two computer-aided design-computer-aided manufacturing systems

Aims: This study aimed to evaluate the marginal and internal discrepancy of the zirconia coping fabricated by two dental computer-aided design-computer-aided manufacturing (CAD-CAM) systems. Settings and Design: In vitro comparative study. Materials and Methods: Twenty zirconia crowns fabricated from inCoris ZI by Cerec InLab CAD-CAM system (Dentsply Sirona Inc, USA) and Ceramill ZI by Ceramill CAD-CAM system (Amann Girrbach, Austria) were measured the discrepancy at six locations using silicone replica technique. Absolute marginal discrepancy (AMD) and marginal gap (MG) represent the marginal discrepancy, and the other four locations at chamfer area, axial wall, cusp tip, and occlusal adaptation represent the internal discrepancy. The gap was measured using an optical light microscope at ×50 magnification. Statistical Analysis Used: The data were analyzed using two-way ANOVA and Game-Howell post hoc test. Results: The statistical analysis showed that the accuracy of zirconia coping depends on CAD-CAM system and the location of measurement. Cerec InLab showed the marginal discrepancy of the coping 119.5 ± 44.8 μm at MG position and 125.3 ± 36.6 μm at AMD position, which was statistically larger than Ceramill system did at 53.0 ± 12.1 μm and 67.2 ± 19.1 μm. On the other hand, the discrepancy in other positions showed no statistical difference between the two CAD-CAM systems. Conclusions: The accuracy of zirconia coping was significant affected by CAD-CAM system and the location of measurement.