Influence of coloring techniques and cement opacity on the optical properties of high translucent monolithic zirconia

Abstract

Background: With the improvement of CAD/CAM technology and translucency of zirconia material, the full contour zirconia crown was introduced to offer dentists a metal free, high strength, and acceptable esthetic prosthesis option. In addition, it is claimed that it is possible to make a full contour high translucent zirconia crown close to natural tooth color by using coloring liquid. However, there is little information in the literature regarding the effect of coloring techniques and cement color on the optical properties of high translucent zirconia. Objective :1) To evaluate the effect of the coloring liquid technique on the resulting optical properties of a monolithic high translucent zirconia 2) To evaluate the cumulative effect of the cement color on the resulting optical properties of a monolithic high translucent zirconia. Alternative hypothesis: There is a significant difference in optical properties between the high translucent monolithic zirconia ceramics with different color staining technique. In addition, the use of shaded resin cement has an effect on the final optical properties of high translucent monolithic zirconia ceramics. Materials and methods: 35 specimens of high translucent zirconia (11mm x11mm) with thickness 1mm was divided into 5 groups according coloring technique, as follows: no color, submerge, two layers of painting, four layers of painting, and six layers of painting. All specimens were measured for the Δ E, transparent parameter (TP), and opalescence parameter(OP) by spectrophotometer (CM-2600D) after firing. Forty-two specimens of high translucent zirconia (11mm x11mm) with thickness 1mm were divided into three groups according to cement color, as follows: clear, opaque, and A2. After firing and cementing with ND4 resin Block. The Δ E, TP and OP will be measured by spectrophotometer. Statistics: The data were analyzed with significant level set at 0.05 one way ANOVA followed by pair-wise group comparisons using Fisher’s Protected Least Significant Differences. Result: 1) The shade of cement significantly affected the mean value of ΔE of E-max CAD and BruxZir high translucent zirconia restoration. Using opaque cement combined with E-max CAD resulted in color difference that was above the clinically perceptible level (ΔE> 3.7). 2) With more layers of staining liquid application, the ΔE and value decreased. The six-layered group showed lowest mean delta ΔE value of 22 (0.78). ΔE was significantly different among groups (p<0.0001). The submerged group showed higher ΔE than the all painting groups. Conclusions: Based on the results of the study, the colors of BruxZir high translucent zirconia and E-max CAD restorations were affected by the shade of cement, whereas white opaque resin cement resulted in BruxZir high translucent zirconia more yellowish. The results of the study demonstrated that the staining technique has an influence on value and final color of Lava-Plus high translucent. Therefore, it is recommended to consider staining technique as one of the influential factors on the final color of zirconia crowns.