How the shade of a crown or filling is decided: reading a shade guide, how lighting distorts colour and the mistakes made during selection.
Tooth shade is chosen by holding sample teeth from a guide next to your own. Colour, though, is not a single value: it has brightness, saturation and hue, plus translucency and surface texture. Two samples with the same letter can still differ in one of those, which is why shade selection is a systematic reading rather than a quick glance.
The components of shade
- Brightness, where mismatches are noticed most
- Saturation, usually higher near the neck of the tooth
- Hue, leaning yellow or grey
- Translucency at the incisal edge
- Surface texture, which makes the same shade look different
Why lighting matters
The same tooth looks different in daylight, under an operating light and under warm household bulbs. Because of this effect, shade is taken under neutral balanced light, with the operating lamp turned away, ideally near a window in the middle of the day.
Practical rules
Shade is taken before the teeth dry out, since a dry surface temporarily looks lighter. Comparisons are kept short, bright lipstick and strong clothing colours are covered with a neutral drape, and the neck, body and edge of the tooth may be recorded separately.
Order of treatment
If you plan both whitening and restorations, whitening comes first and the shade settles before anything is made, because whitening does not lighten ceramic or composite. Reverse the order and the new work will end up darker than its neighbours.
Composite versus ceramic
Composite is layered directly and adjusted at the chair, though margins can stain over time, so polish quality matters in bonding work. Ceramic shade is fired in and stays more stable, and with a zirconia crown the opacity of the framework also affects the final tone. At the try in stage, colour can still be adjusted before final cementation.
Digital shade measurement
Some clinics add a digital device or a photograph taken in a standardised light box. A device is not affected by tired eyes or ambient light, so it gives a repeatable value, but transitions, translucency and surface texture are still judged by eye. When the reading and the clinical impression disagree, the try in decides. If photographs are sent to the laboratory, the shade tab should appear next to the tooth as a reference.
How shade changes over time
- Natural teeth darken slightly with age while restorations hold their colour
- Coffee, tea, red wine and smoking accelerate surface staining
- Composite surfaces dull over time and benefit from repolishing
- Gum recession can expose a colour difference at the neck of a crown
- Whitening is not permanent and needs reviewing at intervals
