FIXED PROS - Shade Selection Flashcards
why is shade selection important?
aesthetics
- satisfies the patient and dentist
what are the 3 variables describing how light is perceived to be reflected from the tooth surface?
hue
value
chroma
what is the hue?
describing the most dominant shade of the tooth
A = red-yellow
B = yellow
C = grey
D = red-yellow-grey
what is the chroma?
the saturation of the colour
= the intensity of the hue
what is the value?
the lightness or darkness of the shade
what are the limitations of the shade guide?
- colours differ for each company
- guide is not universal for all restorations
- must use the same shade guide used by the lab - for crowns, dentures
what 3 factors influence the shade decision?
the object
the observer
illumination
how can the object influence shade decision?
the light can be reflected, absorbed or transmitted through/off the object
what is the reflection called if the object surface is smooth? what’s the equation?
specular
angle of incidence = angle of reflection
what is diffusion?
when the surface is rough and reflected light is scattered
what is the illumination?
the standard light source defined by its specific spectral power distribution
what is the most important light source to use?
daylight = sunlight+skylight
what characteristics does the image have from the brain POV? (4)
- invertion
- spherical aberration - shape can be different
- chromatic aberration - lens has to separate the colours
- blind spots = gaps in the image field
describe vision in low light.
- rod cells are activated
= scotopic vision
what are rod cells responsible for?
providing a monochromatic perception
- good vision in low light