Translucency Evaluation of Monolithic Zirconia Prostheses Made by Gel-Deposition Method

Objectives: The purpose of this study was to evaluate the optical translucency of one kind of monolithic zirconia specimens indicated for dental veneers or crowns fabricated by three-dimensional (3D) gel-deposition method (Self-Glazed Zirconia, SGZ, Erran Tech), and to compare them with the conventional blank-milled zirconia specimens and the lithium disilicate glass ceramics, which were made by computer-aided design and computer-aided manufacturing (CAD/CAM) dry-milling process (Zenostar, WZ, Wieland Dental) and heat-pressing method (IPS E.max Press, LD, Ivoclar Vivadent AG), respectively.
Methods: Forty A2-color ceramic specimens in a size of 14×14×0.6mm were fabricated and were divided into five groups (n=8): (1) SGZ with high translucency (group SGZ-HT); (2) SGZ with low translucency (group SGZ-LT); (3) conventional blank-milled zirconia (group WZ); (4) LD with high translucency (group LD-HT); (5) LD with low translucency (group LD-LT). A spectrophotometer (X-rite color i7600, Gretag Macbeth) was used to measure the percentage of total transmittance of light (T_t%) within the wavelength range of 360-780nm and the CIELAB coordinates of specimens placed on white and black backgrounds, and the translucency parameter values (TP) were calculated. Data were statistically analyzed using one-way ANOVA and Bonferroni test (α=0.05).
Results: Both the T_t% and TP values showed the tendency of the group LD-HT> group SGZ-HT> group LD-LT> group SGZ-LT> group CZ (P<0.05). The average T_t% ranged from 29.8% to 50.2%, the TP values ranged from 15.2 to 25.7 (P<0.05). No significant differences were found in the T_t% and the TP values between the group SGZ-HT and the group LD-LT (P>0.05).
Conclusions: The self-glazed monolithic zirconia specimens fabricated by a novel 3D additive gel-deposition process showed better translucency than the conventional CAD/CAM dry-milled monolithic zirconia specimens. The self-glazed monolithic zirconia prostheses with high translucency might offer similar esthetic appearances to the lithium disilicate glass ceramics with low translucency.