Digital microscopic evaluation of vertical marginal discrepancies of CAD/CAM fabricated zirconia cores

Objective: The aim of this in vitro research study was to evaluate the vertical marginal discrepancies of zirconia (Zr) cores fabricated by five different computer-aided design and manufacturing (CAD/CAM) systems using a digital microscope. Materials and methods: A total of 60 specimens were prepared and randomly divided into five groups (n = 12 each) using the following systems: Ceramill Motion 2 (CM, Amanngirrbach, Germany); Weiland (WI, Ivoclar Vivadent, USA); Cerec (CS, Sirona Dental, USA); Zirkonzahn (ZZ, Gmbh Bruneck, Italy) and Cad4dent (CD, Canada). The specimens were numbered and the vertical marginal discrepancies were evaluated with a digital microscope at 50x magnification. Results: A one-way analysis of variance showed a statistically significant difference (p = 0.002) between the groups. The CM group exhibited the lowest values for the marginal gaps (31.30 +/- 15.12 mu m), while the ZZ group exhibited the highest values for the marginal gaps (44.83 +/- 28.76 mu m) compared to other groups. A post hoc Tukey's test for - multiple comparisons between the experimental groups showed a statistically significant difference (p < 0.05) between the group CM and group CD with group ZZ. The rest of the groups showed no significant differences between them. Variations in the values were observed for the four sites measured with the highest and the least mean marginal gap value of 43.19 +/- 23.84 mu m and 32.49 +/- 12.21 mu m for buccal and lingual sites, respectively. Conclusion: Variations existed in the marginal discrepancy values for the CAD/CAM systems investigated in the study. Vertical marginal discrepancy values observed for various systems investigated in the study were well within the clinically acceptable range.