Effect of Total Occlusal Convergence Angle and Rounded Preparations on the Marginal and Internal Fit of Incisor Monolithic Zirconia Crowns

PURPOSE: To evaluate the marginal and internal fit of anterior monolithic zirconia crowns fabricated over preparations with different TOC angles with and without a rounded incisal design. MATERIALS AND METHODS: Crown preparations of fourteen maxillary central incisors were digitally designed and fabricated using photosensitive resin. The axial wall inclinations were -8°, -4°, 0°, 8°, 12°, 16°, 22° with and without rounded incisal corners and a 1-mm-wide chamfer-type finish line. Monolithic zirconia crowns (n=10) were milled and assessed for fit using the dual-scan technique using an intraoral scanner. The STL files were analyzed in Geomagic Control X, measuring fit at 100, 150, and 175 points on the incisal, axial and marginal areas, respectively. Data normality was tested (Shapiro-Wilk), and TOC angle groups were compared using One-way ANOVA, Levene's test, Tukey HSD, and Independent Samples T-tests (p