X-Rite has provided the "Vita Classic Tab" database for measuring Vita Classical shade tabs. Other Shade-X databases (Vita 3D Master, Chromascop, Empress CAD, etc...) have been optomized to read human teeth only and cannot be used to read shade tabs. The only shade tab that can be read by Shade-X is the Vita Classical shade guide.
There are some added considerations when measuring a Vita Classical shade guide:
While shade guides appear visually to be very consistent from guide to guide, there are deifferences that can be best detected by a sophisticated color measurement device such as X-Rite's Shade-X or ShadeVision. In fact, Shade-X users can use their instrument to check their shade guide for consistency over time or from batch to batch. Shade-X is designed to read human teeth and deliver a quick and accurate shade assignment to the user. Measuring a new Vita Classic tab can restore the user's confidence that the instrument is measuring properly but the real proof is a visual acceptance of the human tooth shade assignment. Shade-X should not be evaluated on its ability to read a particular shade guide tab that might or might not be an accurate sample.
Additional information on this can be accessed in the Additional Information at the bottom of this window entitled: "Shade-X Best Practices".