Fracture resistance and marginal fit of the zirconia crowns with varied occlusal thickness

PURPOSE: The present study aimed to evaluate the clinical applicability of monolithic zirconia (MZ) crowns of different thickness via determination of fracture resistance and marginal fit. MATERIALS AND METHODS: MZ crowns with 0.5, 0.8, 1.0, and 1.5 mm thickness and porcelain fused to metal (PFM) crowns were prepared, ten crowns in each group. Marginal gaps of the crowns were measured. All crowns were aged with thermal cycling (5 – 55℃/10000 cycle) and chewing simulator (50 N/1 Hz/lateral movement: 2 mm, mouth opening: 2 mm/240000 cycles). After aging, fracture resistance of crowns was determined. Statistical analysis was performed with one-way ANOVA and Tukey's HDS post hoc test. RESULTS: Fracture loads were higher in the PFM and 1 mm MZ crowns compared to 0.5 mm and 0.8 mm crowns. 1.5 mm MZ crowns were not broken even with the highest force applied (10 kN). All marginal gap values were below 86 µm even in the PFM crowns, and PFM crowns had a higher marginal gap than the MZ crowns. CONCLUSION: The monolithic zirconia exhibited high fracture resistance and good marginal fit even with the 0.5 mm thickness, which might be used with reduced occlusal thickness and be beneficial in challengingly narrow interocclusal space.