Evaluation of the optical properties of monolithic zirconia of different thickness and translusency with different abutment types

The aim of the study was to evaluate the optical properties of the new generation highly translucent featured 3Y-TZP and 4Y-TZP monolithic zirconia (MZ) veneers with different thicknesses and different abutment types. In the present study; A1 shade MZ blocks (IPS e-max ZirCAD, Ivoclar Vivadent) with two different translucencies (MT, LT) were used. 80 specimens (n=10); with 0.5 mm, 1 mm, 1.5 mm, 2 mm thickness were obtained using a cutter device (Microcut 125 Low Speed Precision Cutting Metkon, Turkey). Veneer groups: LT, MTS (MT Cervical), MTM (MT Medial), MTI (MT Insical); and abutment groups: Zirconia, Hybrid, Titanium, Blue Anodized Titanium (AT), Light Yellow AT, Yellow AT and Pink AT were performed. The first color values L0*, a0* and b0* of the samples and L1*, a1* and b1* values with the abutments were determined by a colorimeter (ShadeEye NCC, Shofu, Japan). The color differences (∆E00*) between the two measurements were calculated according to the CIEDE2000 formula. Statistical analyzes were performed with Three-Way Anova and Fisher's LSD Test (P ˂0.05). Evaluating the results; significant differences were revealed in L1*, a1*, b1* and ∆E00* values according to different zirconia thicknesses, veneer material and abutment type (p <0.001). L1* values exhibited significant differences (p<0.001)in LT veneer groups than other veneers. The highest L1* and b1* values were observed in 0.5 mm Group Z-LT. The lowest ∆E00* values were detected in Group Z-LT in 0.5, 1, 1.5, 2 mm thickness as 3.32, 2.33, 1.66, 1.69 respectively. The highest ∆E00* values were determined in Group M-MTS in 0.5, 1, 2 mm thickness as 17.99, 11.96, 8.48 respectively and Group P-MTS as 9.78 ∆E00* in 1.5 mm thickness. 'Clinically acceptable' color change were obtained only with 1.5 and 2 mm thick of Group Z-LT. Using a low translucency LT veneer material at a thickness of at least 1.5 mm does not cause an 'acceptable color change' in the color of the restoration. Clinicians should keep in mind both translucency and thickness of veneer material and also abutment type if the color modification of the restoration is needed. Keywords: Monolithic zirconia, abutment, color, translucency