Shade Basics Series – Metamerism
Mitch Bourgeois, CDT
Mitch Bourgeois, CDT, explains the phenomenon of metamerism and its effect on shade matching.
Welcome to the O’Brien Shade Basics. What is the most difficult tooth in the mouth to shade match correctly? Well, that may be the wrong question. Does that question imply something that we may not be able to achieve? Without a doubt, the hardest tooth in the mouth to accurately match is a single central and part of the challenge is the expectation to match it. In most cases, the better vocabulary to use would be to speak of shade blending.
So, what do I mean? “Metamerism” the matching of apparent color of objects with different spectral power distributions. Or, another way of saying it, when objects of different material or composition look the same under one light source but different under another.
This is the challenge of what we commonly refer to as shade matching. A shade is taken in an office under one lighting condition, the restoration is perhaps created under a different lighting condition, and the patient sees their restoration under an endless array of lighting conditions.
And under every different light source, a restoration will look slightly different; sometimes better, sometimes worse. Because the dental ceramic and the natural teeth are made of different stuff, they will not react the same under every type of light. What may match perfectly under one lighting condition, may look completely different under another.
So, what we really strive for is the best compromise under the most common conditions and realistic expectations under the most difficult of situations; the single central. Taking a shade under full-spectrum 5,500K color-corrected lighting will give the most reliable blend under most lighting conditions. And, obviously, success increases dramatically when teeth are done in pairs; 8 and 9, 7 and 10 or when multiple restorations are done. But when that single is done, especially in the anterior, the target is more accurately communicated as shade blending rather than matching. Because of metamerism, color perception will change under differing conditions.
A perfect “match” is wonderful when it happens, but that match will look different in a differently lighted environment. Our goal then should be expressed as a restoration that harmonizes with of the rest of the dentition, and under the most lighting conditions. Until next time, I’m Mitch, for O’Brien Dental Lab.