Principles of Color Science in Dentistry and dental ceramic restorations Flashcards
What factors are important for the appearance of teeth and restorations
Size
Shape
Interactions of illumination
What are the interactions of illumination?
Gloss
Translucency
Color
Gloss
The amount of light reflected at the surface of material; with consideration also of the dispersion or scattering of the reflected light from the specular angle of refletion
T/F - instruments are available to measure gloss
True - but most instruments do not precisely cover the entire range of possible gloss values
What are the ways to recommend gloss for clinical evaluation?
Know the shape of the illuminant
Assess the quantity of reflected light
Assess the quality of reflected light
What are the 3 levels of translucency?
Opaque
Translucent
Transparent
Opaque
Light cannot pass through the material
Material masks any underlying color
Translucent
Light, and therefore color, pass through the material, but is partly absorbed, scattered, or both
Transparent
Light and color pass through the material unaltered
Translucency of human enamel
Light tries to travel through, but the curvature of the tooth can reflect light
What are the 3 components of color observation?
Illuminant
Object
Observer
Spectrum of light
Illuminant, the object, and the light entering the eye are each spectral, comprising energy at every visible wavelength
The visible wavelengths extend from 380 nm (just above UV) to 780 nm (just below infrared)
Any light below 380 nm or 780 nm is perceived as what?
Black
Observer
Although the light entering the eye is spectral, the 3 different types of cones of the eye simplify this spectrum into 3 aspects, or 3 dimensions of color
What are the 3 dimensions of color?
Lightness/Value
Two dimensions of chromaticity (hue and chroma)
Lightness/Value
What we consider to be the ‘color’
Chroma
The spectrum that goes from gray to a more vivid color
What color change value is perceivable?
For tooth colors, the limit of perceptibility is ~2 CIELAB units
What color change value is acceptable?
In dentistry, a CIELAB color difference of less than 3-5
What are some examples of color temperature?
1,800K = Red-orange 3,000K = Yellow 5,555K = White 25,000K = Bluish-white
Rendering Index
Describes how the colors of objects under the illuminant differ from the colors of the same objects under a standard (daylight) illuminant
The closer to 100, the more the colors of objects look like they do under daylight
Metamerism
Two objects
No (or negligible) color difference under some illuminant
Color difference under other illuminant
What does scattering cause?
A change in direction of the light
Eventually the light scatters so much, the direction of the light reverses
What does absorption cause?
A lowering in the intensity of the light
Chormatic pigements have absorption which is highly dependent on wavelength
High ratio of absorption/scattering causes what?
Low lightness (dark)
Low ratio of absorption/scattering causes what?
High lightness (bright)
T/F - Absorption and scattering are each spectral
True
High absorption and/or scattering leads to what?
Low translucency (High opacity)
Low absorption AND scattering leads to what
High translucency
