Influence of surface layer removal of shade guide tabs on the measured color by spectrophotometer and spectroradiometer

Objectives To determine the changes in color parameters of Vitapan 3D-Master shade guide tabs by a spectrophotometer (SP) or a spectroradiometer (SR), and by the removal of the surface layer of the tabs that was performed to make a flat measuring surface for the SP color measurement. Methods Color of the shade tabs was measured before and after removing the surface layer of the tabs using SP and SR. Correlations between the color parameters between the original (OR) and the surface layer removed (RM) tabs and between the SP and the SR measurements were determined (α = 0.05). Results Based on SP, the lightness, chroma, CIE a* and b* values measured after the surface layer removal were higher than those of the original tabs except a few cases. Based on SR, the chroma and CIE a* and b* values measured after surface layer removal were higher than those of the original tabs except a few cases; however, in case of the lightness, the changes varied by the shade designation. Type of instrument influenced the changes in color parameters based on paired t-test (p < 0.05). The color parameters of the OR and RM tabs showed correlations based on both SP and SR measurements (r = 0.952–0.997 and p < 0.01); however, color difference between the SP-RM and SR-OR tabs was in the range of 18.1–27.0 image units (mean: 23.3 ± 2.2). Conclusions When the color of tooth-shaped objects is measured with a spectrophotometer or a spectroradiometer, measurement protocols should be specified because color difference by the surface layer removal and the instrument was high.