Purpose: To measure the variations in L*a*b* values of a group of 25 shade guides, and to assess whether shade guides are indeed interchangeable.

Methods: The L*a*b* values of individual shade tabs were measured with a LabScan XE scanning spectrocolorimeter (Hunter Associates Laboratory)with a special attachment for reproducibly positioning shade tabs. One shade guide was arbitrarily selected as a “standard”, and 25 shade guides were compared to this standard. Each shade guide (Vitapan Classical, Vident.) contained 16 shade tabs. Reproducibility of the measurements was determined by measuring and then removing each shade tab of the standard 10 times. The tabs of each of the 25 shade guides were measured five times. All measurements and calculations of DE, L*, a*, b* were performed with the Universal software V4.10. (Hunter Associates Laboratory)

Results: For the “standard “, using the minimum and maximum observations of L*,a*, and b*, for each 16 shade tabs, av DE = 0.7 (0.3) For the group of 25 shade guides, DE = 2.9 (1.3) The difference between the two means is significant at p<0.05 The largest reproducible DE observed was 6.5 for shade C1.

Conclusions: The differences observed between shade guides is larger than the variations induced by the experimental method. The DE value between shades C1 and C2 is 4.8, hence a variation of 6.5 between shade tab of the same shade is clinically significant. The practice of sending the actual shade tab to the dental laboratory appears to have merit.

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