Shade: more is lost communicating it to the laboratory than in taking it

Shade matching is the first thing the patient judges and the last thing time is invested in. Taking the shade averages under a minute, and the information sent to the laboratory is often a single code.

The first problem concerns viewing conditions. Ideal light has a colour temperature around 5500 Kelvin and a colour rendering index above 90; operatory lights are cooler and distort perception, particularly of warm tones.

Retinal fatigue is documented and rapid: after five to seven seconds of fixation, perception shifts. Shade taking should be done in short intervals, looking away at a neutral surface between comparisons.

The neutral grey on which to rest the eye is not a theoretical nicety: without it, one tends to choose progressively more saturated shades because sensitivity to the complementary colour declines.

Timing matters. The shade should be taken at the start of the appointment, before rubber dam or dehydration from prolonged opening lightens the tooth. A dehydrated tooth can appear up to two shades lighter, and the colour returns after some hours.

This produces the most frustrating case: a crown that matches perfectly at delivery and is obviously too light three days later. The crown has not changed; the tooth has rehydrated.

Shade guides have structural limits. The classical VITA distribution does not cover colour space evenly, and some regions — particularly light, low-chroma tones — are poorly represented.

Arrangement ordered by value, as in the 3D-Master guide, makes selection more systematic: value first, then chroma, then hue. It is a sequence that reduces error because it follows the order in which the eye discriminates.

Value is the most important parameter and the one most often wrong. A crown with correct hue but wrong value is immediately obvious; one with correct value and slight hue difference goes unnoticed.

A practical method for assessing it is to squint: colour perception is reduced and the difference in brightness remains, becoming immediately apparent.

Communication to the laboratory is, however, where most information is lost. A single code describes a uniform colour, whereas a natural tooth has different value at the cervical, body and incisal regions, areas of translucency and often characterisations.

A photograph with the shade tab framed beside the tooth resolves much of the problem: it supplies a known reference allowing the technician to correct the image's colour cast. A photograph without a reference is worth less than a code, because on-screen colour depends on lighting and monitor.

In summary: take the shade at the start before dehydration, assess value first, rest the eye on neutral grey, and always send a photograph with the tab alongside. The extra time is two minutes, and it reduces remakes more than any material.