Color compatibility between two shade guides

Objectives: To develop an accurate conversion chart between VITA classical A1-D4 (VC) and VITA Linearguide 3D-Master (LG) shade guides (VITA Zahnfabrik), and to evaluate color compatibility through determining the first, second and third best match from one shade guide to another.
Methods: Spectral reflection values for each VC and LG shade tab (n=3) were collected using spectroradiometer (PR-670, PhotoResearch), using D65, 2°. Color compatibility between VC and LG was evaluated through coverage error (DE*_COV), and calculated as mean of best matches (SDE*_MIN/n, smallest DE* values) of one shade guide to another. Lower coverage error corresponded to better match. In addition to DE*_COV (the best match), the second and third best matches of one shade guide to another were determined. Means and standard deviations were calculated and data were analyzed by analysis of variance with Tukey-Kramer multiple comparison test (a=0.05).
Results: The DE*_COV (s.d.) of VC to LG was 3.3 (2.5), while the means of the second and third best matches were 4.2(2.5) and 5.6(3.2). The means (s.d.) of the first, second and third best matches of LG to VC were 1.7(0.8), 2.8(0.6) and 3.2(0.5), respectively. Tukey-Kramer intervals for comparisons among two shade guides and best matches was 0.8 and 1.0, respectively, revealing significantly better coverage of VC with LG than vice versa (p<0.001). There were significant differences between the first and third (p<0.001), and second and third best match (p<0.05).
Conclusions: Color compatibility of VITA Linearguide 3D-Master to VITA classical A1-D4 was significantly better than vice versa. The coverage error of LG to VC was below the 2.7 threshold.