Spectrophotometric evaluation of color match of three different porcelain systems for all-ceramic zirconia-based restorations

Purpose: To determine by a spectrophotometric analysis the variations in color between the intended and the fabricated shades of three different porcelain systems when applied in a standardized thickness on a zirconia core. Methods: Three porcelain systems for zirconia based restorations, Ivoclar IPS e.max Ceram, VITA VM9, and Creation Zi-F were tested. Nine disc-shaped (15 mm diameter, 0.5 mm thickness) specimens of VITA YZ zirconia core per group were made comprising a total of 27 discs. Three different shades (A2, A3, A4) of the Vitapan Classical shade guide were investigated. The porcelain veneer total thickness was set at 1.0 mm in all groups. The porcelain stratification was made by applying calibrated layers of porcelain. Thicknesses of single porcelain layers were calculated from drawings retrieved from the manufacturers' instructions. Color parameters (L*, a*, b*) of veneered specimens were measured by a clinical spectrophotometer. Color differences (AE) were calculated using a color difference formula. Two-way ANOVA and Tukey's test were used to analyze the data. Results: The mean color differences for the three ceramic systems, Ivoclar IPS e.max Ceram, VITA VM9 and Creation Zi-F were respectively 4.1, 2.7 and 3.2, regardless of the shades. VITA VM9 resulted in the best average shade matching among the porcelain systems, even if results with shade A3 were considerably worse than shades with A2 and A4 (P< 0.05). Color matching appeared not to be shade dependent (P> 0.05) among the tested shades.