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

Abstract

To compare the marginal accuracy of zirconia crowns fabricated by different workflows (conventional and digital) and designs (monolithic and veneered). 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). The most superior vertical marginal accuracy was observed for IOS-V (mean= 22.5μm; SD = 6.7μm), followed by IMP-V (mean= 23.9μm; SD = 7.8μm), IOS-M (mean = 28.7μm; SD = 10.3μm), and IMP-M (mean = 39.8μm; SD = 22.0μm), respectively (p < 0.001). The IOS-M had the greatest mean horizontal discrepancies (mean = 23.9μm; SD = 4.3μm) followed by IMP-M (mean = 21.3μm; SD = 5.7μm), IMP-V (mean = 19.2μm; SD = 5.3μm) and IOS-V (mean = 17.6μm; SD = 5.7μm) (p < 0.001). 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.