Shade matching by eye is one of the least reproducible procedures in dentistry, and the reasons have nothing to do with the skill of the observer.
Why the eye is unreliable here
Colour perception shifts within seconds of staring at a tooth, as the retina adapts. It changes with ambient lighting, with the colour of the wall behind you, and with what the observer has been looking at previously.
It also changes across the working day with visual fatigue. The same clinician can record different shades from the same tooth at nine and at five.
The problem with shade guides
Conventional guides sample colour space unevenly, leaving regions with no close match. The tab you choose is frequently the nearest available rather than the correct one.
And a tab is a flat piece of ceramic. A tooth has depth, varying translucency and internal characterisation that no single tab represents.
What instrumentation adds
A dental spectrophotometer returns objective coordinates with far higher reproducibility, and allows the difference between the target and the finished restoration to be measured rather than debated.
Its limitation is that it reads small areas and captures translucency and internal effects poorly, which is why it supplements rather than replaces trained observation.
The protocol that works
Instrumental measurement as the objective anchor, cross-polarised photography with the shade tab in the same plane to show the ceramist the internal structure, and visual verification early in the appointment under standardised light.
Recorded before the teeth dehydrate, which lightens them by several shades within minutes of isolation.
If shade was taken at the end of a long appointment, under the operating light, on dehydrated teeth, it was recorded under the three worst conditions simultaneously.
To determine whether this procedure is indicated in your particular case, we invite you to request a clinical assessment.
