Introduction
Optical properties decide how natural a restoration looks. They result from how a material interacts with light, and how the eye and brain perceive it. Visible light has wavelengths of 380 to 760 nm, and white light contains all of them.
Color
Color depends on how a material absorbs and reflects light. An object that absorbs all light looks black, and one that reflects all of it looks white. Selective reflection of some wavelengths gives chromatic colors.
In the Munsell system, colors sit in a sphere. Hue runs around it, chroma grows from the center outward, and value rises from black at the bottom to white at the top. Natural teeth occupy a small area of red-yellow hues, with high value and low chroma.
Matching tooth color
Shade is matched by eye with shade guides, or objectively with a dental spectrophotometer, which uses its own constant light.
Pitfalls in shade matching
- Metamerism: two colors match under one light but not under another. Match in daylight, ideally between 10:00 and 16:00, and check under different lights.
- Colored surroundings: clothes and walls change the reflected light, so surgery walls should be white or gray.
- Color fatigue: looking too long dulls the eyes. Work quickly, and rest your eyes on something green or blue.