الفهرس 
ACKNOWLEDGMENTOnly 14 pages are availabe for public view
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Abstract
This in vitro study evaluated the biaxial flexural strength and optical behavior (translucency and shade accuracy) of CAD/CAM multichromatic ultra-translucent zirconia and compared it with multichromatic high translucency Lithium Disilicate glass-ceramic.
Fourty ceramic specimens were fabricated from the two materials & were divided into two main groups; group I: CAD/CAM multichromatic ultra-translucent Zirconia (UTML KATANA Zirconia) and group II: Pressable multichromatic high translucent Lithium Disilicate glass-ceramic (e.max press multi). Each group was then subdivided into two subgroups; subgroup A: disc specimens (12mm diameter×1.5mm thickness) were fabricated (n=10) and thermocycled (500 cycles, 5°/55°C, 15 sec dwell time).Then, biaxial flexural strength (Ball on ring test) was measured in MPa. Subgroup B: rectangular specimens (12mm length × 10mm width × 1.5mm thickness) were fabricated (n=10). Color parameters were evaluated according to the color system CIE L*a*b*, three times for each quarter of the specimens corresponding to the four zones of multilayered specimens on both black and white backgrounds using Spectrophotometer VITA Easyshade@ Advance. Translucency was evaluated with translucency parameter (TP). Then, the twenty rectangular specimens were cemented to composite specimens (simulating dentin of natural teeth) by translucent resin cement to evaluate shade accuracy. Color parameters for each specimen were measured post cementation three times on each quarter corresponding to the four zones of multilayered specimens. Then, they were compared to color parameters of shade A2 vitapan classical shade guide and ΔE was calculated.
UTML KATANA zirconia group showed higher statistically significant biaxial flexural strength values than IPS e.max Press Multi group. However, IPS e.max Press Multi group showed higher statistically significant translucency and shade accuracy than UTML KATANA zirconia group.
In conclusion, Monolithic zirconia materials showed statistically significant superior biaxial flexural strength values than the lithium disilicate glass ceramics. Multi-coloured zirconia block showed four layers with different light transmittance capabilities. It might therefore be useful for enhancing the aesthetic appearance of full-contour zirconia restorations made from this material. UTML katana zirconia was significantly less translucent and less shade accurate than lithium disilicate glass ceramics.