Color Measurements Harmonization Between Instruments Utilizing 45/0 Geometry: Pilot Study

Objectives: Color measuring instruments are calibrated with different standards causing discrepancies among measurements from different instruments. The aim of this pilot study was to develop Correction Factors (CF) in order to harmonize results obtained with different instruments with 45/0 optical geometry, using sets of translucent specimens made of CAD/CAM materials.
Methods: A variety of dental materials were used to create square-shaped (10×10mm, 1.0mm –thick) specimen sets A-O and I-X (15 and 10 groups of specimens, respectively; n=5 per group), with variability in shades (light, medium, dark) and translucencies (medium, high). Non-contact measurements were performed at the middle portion of specimens using two spectroradiometers with the 45/0 optical geometry: reference measurements (RM) – at coordinating center, and site measurement (SM). Upon comparison of RM and SM reflection data, CF was calculated for SM. Color differences were calculated using CIE1976 formula. Means and standard deviations were calculated. ANOVA and Fisher’s PLSD test was used to compare color differences (ΔE*) at α = 0.05.
Results: Means (sd) of color differences (ΔE*) between RM and non-corrected SM (SM_NC), RM and corrected SM (SM_CORR), and between SM_NC and SM_CORR, are presented in the table.CF enabled significant decrease of color differences between RM and SM for both A-O and I-X sets (p<0.05 and P<0.001, respectively). Fisher’s PLSD intervals at the 0.05 level of significance for comparisons of mean ΔE* values for A-O and I-X set non-corrected vs. corrected c were 0.59 and 0.37, respectively.
Conclusions: Within the limitation of this pilot study, correction of site measurements with Correction Factor significantly increased agreement between different instruments with 45°/0° optical geometry when measuring translucent dental materials.