shade selection

Question 1

what is the definition of colour

Answer 1

a sensation of light induced in the eye by EM waves of certain frequency

Question 2

what is the frequency of colour

Answer 2

380-780nm

Question 3

what is needed to make colour

Answer 3

1. Sample
   
   2. Light source
      Light sensor + image projector

Question 4

what do we need in the context of dentistry to make light

Answer 4

1. Object
   
   2. Illuminant
      Observer

Question 5

what can happen to light when it strikes an object

Answer 5

reflected
absorbed
transmitted

Question 6

when does the angle of incidence and the angle of reflection equal

Answer 6

if the surface is smooth

Question 7

what is seen if the angle of incidence and the angle of reflection is the same

Answer 7

specular reflection

Question 8

what can happen if the surface is slightly rough

Answer 8

diffusion of light

Question 9

what do natural teeth show when they are wet

Answer 9

specular reflection

Question 10

what type of light shall we use to correctly shade match

Answer 10

clinic light as natural daylight changes in the day

Question 11

what are the two types of vision

Answer 11

scotopic vision

photopic vision

Question 12

what is scotopic vision

Answer 12

Only rod cells are sensitive at low light levels
Light/dark perception / monochromatic
Full sensitivity after 30 mins

Question 13

what is photopic vision

Answer 13

Cone cells sensitive

Full colour range

Question 14

how does chromatic adaption occur

Answer 14

Caused by the response of the eye changing with time

Several minutes are required for the cone cells to become stable

Question 15

what shade guide to dentists use

Answer 15

VITA shade guide

Question 16

how is the vita shade guide used

Answer 16

Which is split into 4 groups:
A - brown shades A1-->A4 increasing the depth of colour 
B - yellow group
C - grey group 
D - reddish hue

Question 17

how do dentists use the shade guide

Answer 17

1, first decide what group the tooth is in
2. then check with the other teeth
be mindful of retinal fatigue

Question 18

what is retinal fatigue

Answer 18

hard to identify colours after a while so we can fix this by looking at a neutral colour for a little while eg blue beds

Question 19

what are the disadvantages of the vita shade guide

Answer 19

The tooth doesn’t have a uniform colour from the cervical to the incisal edge
So not the perfect solution

Question 20

what equipment can we use to get a more accurate colour guide

Answer 20

Spectrophotometer
Enabled an image to be built up
And a weather map can be build up of different colours