Ips e max cad ht block

The translucency of the ceramics was determined on double-sided mirror-glass polished specimens (n=10, thickness of 0.5 mm) using a spectrophotometer (SpectroShadeTM MICRO, MHT Optic Research, Niederhasli, Switzerland). Lithium-disilicate glass-ceramic (LS2) specimens (n=7, thickness of 0.5 mm) were prepared from an IPS e.max CAD HT block (Ivoclar Vivadent, Schaan, Liechtenstein; "HT" = high translucency) as a translucency reference control. The spectrometer was used to record the CIELAB coordinates (L*, a* and b*) of each ceramic disk positioned on a black and white background. A thin layer of vaseline was put in between specimen and background for better optical contact. The translucency parameter (TP) was calculated according to:
where the subscripts B and W refer to the color coordinates over a black and white background, respectively [20] (link).

The translucency of the ceramics was measured on a double-sided mirror-polished plate specimens (n = 7, thickness = 0.5 mm) using a spectrophotometer (SpectroShadeTM MICRO, MHT Optic Research, Niederhasli, Switzerland) before and after 60 h of hydrothermal aging. Lithium-(di)silicate glassceramic (LS2) samples (n = 7, thickness = 0.5 mm) were fabricated from IPS e.max CAD HT block (Ivoclar Vivadent, Schaan, Liechtenstein; "HT" = high translucency) as translucency reference control. The spectrometer was used to record the CIELAB coordinates (L*, a* and b*) from the specimens positioned on a black and white background. A thin layer of vaseline was put in-between specimen and background for better optical contact. The translucency parameter (TP) was calculated according to:
with subscripts B and W representing the coordinates over a black and white background, respectively.
The spectral reflectance (Y), obtained from the L* values, over black and white backgrounds were additionally used to calculate the contrast ratio (CR) following equation [26] (link):
CR linearly correlates with TP [27] (link). A high TP represents high translucency and low CR, and vice versa.
More specifically, CR is 0.0 for a transparent material and 1 for a completely opaque material.