Development of a customized whiteness index for dentistry based on CIELAB color space.

Objectives: To develop a customized CIELAB-based whiteness index for dentistry that accurately correlates to perception of tooth whiteness.

Methods: Four psychophysical experiments (PE1-4) were conducted by three panels of observers (OP1-3) under diffuse/0° observation/measuring conditions and under typical clinical viewing conditions. Nine whiteness indices (WI, Z%, WIC, WIO, W31, W64, W, WLAB, W*), two yellowness indices (YID1925, YIE313) and tint of white in the CIELAB color system (T) were compared with regard to their ability to measure the perceived whiteness of human teeth. Determination coefficient (R(2)) and '% wrong decision' (%WD) method were used as direct measures of the quality of the indices for whiteness perception in dentistry.

Results: CIELAB-based whiteness index (WID=0.511L* -2.324a* -1.100b*) was developed through optimization from the data obtained in PE1. The proposed WID performed better than all the CIELAB and CIE1931 XYZ-based indices under laboratory and clinical conditions (only WIO was comparable to WID in PE2 and PE4).

Conclusion: The validation experiments under laboratory and typical clinical conditions revealed that the proposed index WID outperformed previous indices, being the only CIELAB-based index developed for evaluation of whiteness in dentistry.