How do you go about matching a tooth's shade?

The patient shown in the picture has his two central incisors crowned. His shade was fairly easy to match but some are not. Most dentists use dental shade guides to help them choose a shade or shades for a tooth. For most posterior teeth the process that is fairly simple. When choosing a shade, I hold a shade guide adjacent to the tooth in question and look at it briefly, then I choose an alternative shade and look briefly at them next to the tooth.

When evaluating shade buttons the dentist should look at the shade for no more than a second or two at a time. If the shade guide is held against the tooth for longer it starts looking better since our eyes accommodate and we can no longer adequately judge whether the guide used is the correct for a patients tooth. In general I can choose a shade after looking at two or three alternative choices. I also let my patient view my shade button 'challenges' while I'm doing them.

For a shade to look acceptable it must not only match the hue and chroma (color) of the tooth but should be close in value( brightness). If I want to judge the value of a shade I sometimes squint while looking at it, since this essentially eliminates the color component of the shade but still allows me to perceive the black and white portion of the shade( the value).

For anterior teeth the process of picking a shade (or shades) can sometimes be extremely tricky. For tricky shades a dentist or dentist can draw out a shade map on his lab Rx that shows the different sections of the tooth surface and indicate what shades he sees in different zones of the the tooth surface. Also for tricky anterior teeth I often send photographs of the tooth or even send the patient to the laboratory for their shade selection. Sometimes after a crown try in, if I feel it is necessary my patient is sent to the laboratory either custom staining of their crown or so that the ceramicist can view how the crown looks in the mouth and have a better idea of what changes need to be made. For some single anterior teeth being made for discriminating patients or dentists, a ceramicist may even have to make remake the crown several times, before a satisfactory version is fabricated.