FIXED PROS - Shade Selection

Question 1

why is shade selection important?

Answer 1

aesthetics
- satisfies the patient and dentist

Question 2

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

Answer 2

hue
value
chroma

Question 3

what is the hue?

Answer 3

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

Question 4

what is the chroma?

Answer 4

the saturation of the colour
= the intensity of the hue

Question 5

what is the value?

Answer 5

the lightness or darkness of the shade

Question 6

what are the limitations of the shade guide?

Answer 6

• 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

Question 7

what 3 factors influence the shade decision?

Answer 7

the object
the observer
illumination

Question 8

how can the object influence shade decision?

Answer 8

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

Question 9

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

Answer 9

specular

angle of incidence = angle of reflection

Question 10

what is diffusion?

Answer 10

when the surface is rough and reflected light is scattered

Question 11

what is the illumination?

Answer 11

the standard light source defined by its specific spectral power distribution

Question 12

what is the most important light source to use?

Answer 12

daylight = sunlight+skylight

Question 13

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

Answer 13

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

Question 14

describe vision in low light.

Answer 14

• rod cells are activated
  = scotopic vision

Question 15

what are rod cells responsible for?

Answer 15

providing a monochromatic perception
- good vision in low light

Question 16

in low light, when is full sensitivity achieved?

Answer 16

after 30 mins

Question 17

describe vision in high light levels.

Answer 17

• cone cells are activated
  = photopic vision

Question 18

role of cone cells.

Answer 18

provide full colour vision

Question 19

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

Answer 19

• morning or start of appointment
• because eye fatigue is minimal

Question 20

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

Answer 20

61-183cm
from 2-6 feet

Question 21

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

Answer 21

same level as operators eyes

Question 22

what lighting is best for shade selection?

Answer 22

mid-day light

Question 23

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

Answer 23

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

Question 24

what colour background is ideal?

Answer 24

grey

Question 25

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

Answer 25

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