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Objectives:The study was conducted to compare the optical parameters of VM7 ® M-shade base dentin ceramics (VITA, Germany) for all ceramic restorations to the chemical composition across the 3D-MASTER ® shade system. Methods:Three disc samples, 13 mm diameter and 1.4 mm thickness, were produced for each M-shade following the manufacturer's instructions. Each disc was ground and polished to a thickness of 1.0 mm. Spectral light transmittance and reflectance data were recorded in the visible spectrum under the standard illuminant D65 and 2° observer at 10 nm intervals by using a computer-controlled spectrophotometer. Opacity, translucency and opalescence parameters were determined for each sample.Results: 1) Spectral transmittance and reflectance in the short-wavelength range systematically decreased with increasing chroma number (M1, M2, M3) when compared within the same value (lightness) group.2) Spectral transmittance and reflectance decreased systematically across the whole visible spectrum with increasing value group number when compared within the same chroma group. Significance: Systematic variations in optical properties of VM7 ® M-shade base dentin ceramics were observed throughout the 3D-MASTER ® shade system and were suggested to be caused by the fine structure of the sample which can interfere with shorter wavelengths in the visible spectrum.