Effects of dipping time on color parameters, elemental composition and resin cement bonding of monolithic zirconia

This study evaluated the effects of different dipping times on the color parameters, elemental composition, and resin cement bonding of monolithic zirconia.

Uncolored monolithic zirconia blocks (InCoris TZI) were sectioned into 6 × 6 × 2 mm specimens (N = 44) and divided by dipping time in a coloring solution (InCoris TZI Coloring Liquids): control (C), 2 minutes (D-2), 5 minutes (D-5), and 10 minutes (D-10)(n = 10). Color measurements were performed using a dental spectrophotometer, and color differences (ΔE₀₀) were computed using the CIEDE2000 formula. For shear bond (SBS) testing, specimens were embedded, air-abraded, primed, and bonded to resin cement cylinders (diameter: 2 mm, height: 2 mm). SBS testing was performed (0.5 mm/min.). Data were statistically assayed (SPSS 26; One-way ANOVA, Tukey post-hoc tests; P = .05). Failure modes were classified under an optical microscope. Elemental and structural analyses were performed using SEM-EDS and XRD.

Prolonged dipping time influenced color parameters, resulting in increased ΔE₀₀, a*, and b* values, and decreased L* values. A significant difference in ΔE₀₀ was found between D-2 and D-10 groups(P < .05). For SBS test, D-5 group (21.76 ± 6.01 MPa) exhibited significantly higher values than C group (15.38 ± 5.77 MPa) (P < .05). SEM-EDS analysis revealed increased Er concentration and decreased Zr concentration with prolonged dipping times. Corresponding oxide-related peaks were detected by XRD.

Different dipping times significantly affected both color parameters and resin cement bond strength of monolithic zirconia. A 5-minute dipping protocol provided a favorable balance between color change and shear bond strength to resin cement.