Effect of cement-space thickness on the marginal fitness of all zirconium oxide crowns—An in vitro study

Aim: To estimate the influence of cement-space thickness on the vertical marginal fitness of full zirconia crowns. Materials and Methods: A total of 24 newly extracted sound human maxillary first premolars were mounted and thereafter prepared to receive fully contoured zirconia crowns. Teeth were scanned via Chairside Economical Restoration of Esthetic Ceramic (CEREC) digital intraoral scanner (Omnicam, Sirona, Germany). Afterward, teeth were randomly assorted into three groups (depending on the cement-space thickness parameter of their corresponding designed crowns): group A = 80 μm, group B = 100 μm, and group C = 120 μm. Zirconia crowns were assembled using In-Lab MCX5 milling machine (Sirona). The cementation procedure was undergone using RelyX Unicem self-adhesive luting cement (3M, ESPE, Germany). The marginal discrepancy was measured at 16 points/tooth utilizing a digital microscope (85× magnification). Data were statistically analyzed utilizing one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) test (P = 0.05). Results: The analysis revealed that the cement-space thickness parameter had a highly significant effect on the marginal gap values in all groups. The lowest mean of marginal gap values was noted for group C (120 μm). Conclusion: Increasing cement-space thickness from 80 μm to 100 and 120 μm might be favorable for a better adaptation of monolithic zirconia crowns.