FIXED PROS - Shade Selection Flashcards

1
Q

why is shade selection important?

A

aesthetics
- satisfies the patient and dentist

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2
Q

what are the 3 variables describing how light is perceived to be reflected from the tooth surface?

A

hue
value
chroma

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3
Q

what is the hue?

A

describing the most dominant shade of the tooth
A = red-yellow
B = yellow
C = grey
D = red-yellow-grey

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4
Q

what is the chroma?

A

the saturation of the colour
= the intensity of the hue

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5
Q

what is the value?

A

the lightness or darkness of the shade

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6
Q

what are the limitations of the shade guide?

A
  • 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
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7
Q

what 3 factors influence the shade decision?

A

the object
the observer
illumination

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8
Q

how can the object influence shade decision?

A

the light can be reflected, absorbed or transmitted through/off the object

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9
Q

what is the reflection called if the object surface is smooth? what’s the equation?

A

specular

angle of incidence = angle of reflection

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10
Q

what is diffusion?

A

when the surface is rough and reflected light is scattered

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11
Q

what is the illumination?

A

the standard light source defined by its specific spectral power distribution

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12
Q

what is the most important light source to use?

A

daylight = sunlight+skylight

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13
Q

what characteristics does the image have from the brain POV? (4)

A
  • invertion
  • spherical aberration - shape can be different
  • chromatic aberration - lens has to separate the colours
  • blind spots = gaps in the image field
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14
Q

describe vision in low light.

A
  • rod cells are activated
    = scotopic vision
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15
Q

what are rod cells responsible for?

A

providing a monochromatic perception
- good vision in low light

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16
Q

in low light, when is full sensitivity achieved?

A

after 30 mins

17
Q

describe vision in high light levels.

A
  • cone cells are activated
    = photopic vision
18
Q

role of cone cells.

A

provide full colour vision

19
Q

what time of day is ideal for shade selection and matching? why?

A
  • morning or start of appointment
  • because eye fatigue is minimal
20
Q

what is the ideal distance from the oral cavity for shade matching?

A

61-183cm
from 2-6 feet

21
Q

what level should the patient be sat at for shade matching?

A

same level as operators eyes

22
Q

what lighting is best for shade selection?

A

mid-day light

23
Q

what things from the environment should be avoided in order to choose shade selection?

A
  • bright-coloured surroundings
    = if the patient has bright clothing, use a mask
  • no lipstick
  • surfaces with high gloss disturbs the glare
24
Q

what colour background is ideal?

A

grey

25
Q

what should be the condition of the teeth for shade selection?

A
  • tooth and adjacent should be free of plaque, other deposits, stains
  • moist tooth, dehydration makes the tooth whiter