Marginal Fit and Fracture Resistance of Vertical Versus Horizontal Margins in Monolithic Zirconia Crowns.

Objective: The use of vertical margin design in all-ceramic restoration has generated inquiries regarding its clinical efficacy under diverse dynamic oral conditions. This research aims to assess the marginal fit and fracture resistance of monolithic zirconia crowns featuring vertical margin design as opposed to those with conventional horizontal margin design.

Materials And Methods: Two metal dies were employed to generate replicated resin dies mimicking mandibular first molar preparation. The metal dies were precision-engineered with two margin designs: vertical margin design presenting a shoulderless configuration (Featheredge) and horizontal margin design (Radial Shoulder). Forty zirconia crowns were produced on the replicated resin dies using two varieties of monolithic zirconia, with twenty crowns in each category: pre-shaded and multilayered zirconia. Both sets were further subdivided into two groups based on the finish line configuration utilized (n = 10). The vertical marginal gap of the zirconia crowns was gauged before and after thermocycling (5-55oC/5000 cycles), followed by loading the crowns until fracture occurred. Statistical analysis was performed using one-way analysis of variance (ANOVA), accompanied by Bonferroni's post hoc test and independent t-test for pairwise comparisons.

Results: The Shoulder subgroup of BruxZir exhibited the highest mean marginal gap value (120.06 ± 10.15 µ), while the Featheredge subgroup of BruxZir displayed the lowest value (49.72 ± 6.53 µ). Among the BruxZir group, the Featheredge subgroup showcased the highest mean fracture resistance value (4251.57 ± 279.90 N), whereas the Shoulder subgroup recorded the lowest value (1721.60 ± 225.16 N).

Conclusion: Monolithic zirconia crowns with vertical margin design (Featheredge) demonstrated statistically enhanced performance compared to conventional horizontal margin design, as evidenced by lower marginal gap values and increased fracture resistance tolerance.