Optical properties of currently used zirconia-based esthetic restorations fabricated with different techniques

Objective The aim was to evaluate the effects of different types of monolithic zirconia (MZ) and fabrication techniques on the optical properties of newly generated zirconia-based materials after aging. Material and Methods Sixty specimens (n = 10) were prepared. For the groups layering-veneering (LV), overpressing (OP), porcelain fused to zirconia (PFZ), and cutback (CB), 3Y-TZP, IPS e.max ZirCAD was prepared as the core material (0.5 +/- 0.01 mm). For full-contour (FC) technique, 3Y-TZP was used for MZ-LT (low translucency) and 4Y-TZP was used for MZ-MT (medium translucency). L*, a*, b*, chroma (C), and relative translucency (RTP) were measured before (L-1*, a(1)*, b(1)*, C-1, RTP1) and after (L-2*, a(2)*, b(2)*, C-2, RTP2) UV aging. Statistical analyses were performed by one-way ANOVA with Tukey's test and paired sample t tests (P = .05). Results Fabrication techniques significantly affected the L*, a*, b*, C, RTP, and Delta E-00 values (P < .01). The highest L-1* value was found in MZ-LT; followed, in order, by OP, PFZ, LV, CB, and MZ-MT. The highest b(1)* and C-1 values were found in OP, while MZ-MT had the lowest values (P < .05). FC had the highest RTP values for MZ-MT (13 +/- 0.9 RTP1; 11.2 +/- 0.9 RTP2), and the lowest RTP values were found for MZ-LT (8.5 +/- 0.9 RTP1; 8.3 +/- 1.2 RTP2) (P < .01). Aging caused significant differences in the L*, a*, b*, C, and RTP values (P < .05). The color changes were between 0.9 and 2.1 Delta E-00. Conclusions The fabrication technique significantly affected the optical properties. UV aging caused zirconia-based restorations to become darker and more yellow, red, saturated, and opaque. Clinical Implications Fabrication techniques with different zirconia structures affected the optical properties of the restoration, even when the same shades were chosen. If more translucent restorations are needed, choosing 4-YTZP with the FC technique is better than veneering with 3-YTZP. Choosing 3-YTZP with the FC technique produces more esthetic results if brighter and more opaque restorations are needed.