Tooth shade and shape: making the prosthesis fit
A shade guide, daylight and sometimes an old photograph.
For a crown to disappear beside your own teeth, the laboratory has to get two things right: the shade and the shape. Both are established at the practice, not in the laboratory – which is why a lot hangs on that one appointment.
How the shade is determined
The usual tool is a shade guide: a fan of small ceramic teeth in graded brightnesses and hues. The matching one is held next to the neighbouring tooth, usually at the height of the middle of the tooth, because the neck and the incisal edge look different from the surface in between.
More elaborate practices and laboratories additionally work with a measuring device or with photographs in which the shade guide lies directly beside the tooth. For the anterior region that is a noticeable difference, because the ceramic can then be built up in layers instead of in one colour.
Why the timing counts
- Early in the appointment. Teeth dry out under the rubber dam or during a long treatment and become brighter in the process. A shade taken on a dry tooth is too bright later on.
- In daylight. The treatment light distorts. Many practices go to the window for the shade taking.
- Without strong red. Lipstick, a red top or a colourful background shift the perception measurably.
- After whitening. Anyone who wants to bleach does it beforehand and then waits one to two weeks until the shade has stabilised.
Where the shape comes from
With a single tooth the model is the neighbour on the other side – it is mirrored. If several front teeth are missing, it becomes a decision: tooth width, length, how round or angular the corners are, how the teeth stand in relation to the lip.
Old photographs in which you are laughing are helpful. They show what your teeth looked like before anything changed – often a better model than any catalogue.
When it does not fit
Before the final fitting the prosthesis is tried in. That is the moment for objections: too bright, too long, too even. A correction is then routine. Once the crown is cemented, the same change means a new fabrication – and the insurer does not pay for that a second time.
What is still possible after that and when a second opinion makes sense is described under Second opinion on dental prostheses.