The purpose of this study was to determine the validity and accuracy of mixing opaque feldspathic dental ceramic to obtain specific shades using two methods: (1) Concentration Additivity of Optical Parameters (CALAB) and (2) Concentration Additivity of Kubelka-Munk Optical Coefficients (CAK/S). A total of 25 opaque feldspathic dental ceramic specimens were fabricated by mixing six different pure shades in different concentrations. The reflectance spectra were measured and the actual CIELAB L*, a* and b* coordinates were obtained for the 25 specimens. The CALAB and CAK/S methods were used to predict the L*, a* and b* values with reference to the concentrations of the pure shades. Correlation analysis was carried out between the actual and predicted L*, a* and b* values for both methods. The color differences (ΔE*) between actual and predicted L*, a* and b* values were also calculated and analyzed using repeated measures ANOVA. Pearson's correlation coefficients between predicted and actual values for both methods were greater than 0.98. The mean ΔE*s were 0.24 (0.11) for CALAB method and 0.21 (0.11) for the CAK/S method. The repeated measures ANOVA revealed a statistically significant difference (P=0.0213) between the mean ΔE*s from the two methods. Both methods produced mean ΔE*s between the actual and predicted methods that were below the threshold of human perceptibility. The simpler CALAB method can be used to determine the opaque ceramic mixture for specific shades with accuracy.
Bibliographical noteFunding Information:
This study was presented in part at: (1) Annual meeting of the American Association of Dental Research, Chicago, IL, March 2001, and (2) Annual meeting of the American Academy of Fixed Prosthodontics, Chicago, IL, February 2002. The work was supported in part by USPHS Research Grant from the National Institute of Dental and Craniofacial Research (DE-07155013) and National Heart, Lung, and Blood Institute (#K30 NL04162), National Institutes of Health, Bethesda, MD 20892. The authors would also like to acknowledge the assistance of D.N. Robertson, D.D.S a former research student in fabricating and measuring specimens use in the preliminary work for this study.
- Concentration additivity
- Dental materials
- Mixing formulations
- Opaque ceramic
- Optical parameters
- Paradigm shift
- Spectrophotometer measurements