Marginal Accuracy of Monolithic and Veneered Zirconia Crowns Fabricated by Conventional and Digital Workflows.

PURPOSE: To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered). MATERIALS AND METHODS: A prepared maxillary first molar was used for the study. Four workflow combinations were evaluated: (1) intraoral scanning and monolithic zirconia (IOS-M), (2) intraoral scanning and veneered zirconia (IOS-V), (3) conventional impression and monolithic zirconia (IMP-M), and (4) conventional impression and veneered zirconia (IMP-V). All of the specimens had similar designs. The veneered groups had a buccal cutback for esthetic veneer application. A total of 10 crowns were produced in each workflow. The vertical and horizontal marginal accuracies were measured with a traveling microscope. Depending on the normality of the data, one-way analysis of variance test or Kruskal-Wallis test were applied to evaluate the differences among the groups (α = 0.05). RESULTS: The most superior vertical marginal accuracy was observed for IOS-V (mean = 22.5 µm; SD = 6.7 µm), followed by IMP-V (mean = 23.9 µm; SD = 7.8 µm), IOS-M (mean = 28.7 µm; SD = 10.3 µm), and IMP-M (mean = 39.8 µm; SD = 22.0 µm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9 µm; SD = 4.3 µm) followed by IMP-M (mean = 21.3 µm; SD = 5.7 µm), IMP-V (mean = 19.2 µm; SD = 5.3 µm) and IOS-V (mean = 17.6 µm; SD = 5.7 µm) (p < 0.001). CONCLUSIONS: Monolithic zirconia crowns fabricated digitally had superior marginal accuracy than monolithic zirconia crowns fabricated conventionally. Esthetic buccal veneering of predominantly monolithic zirconia copings improved the vertical and horizontal marginal accuracies.