Colour Management

Question 1

What is the colour of the shortest and longest wavelengths of visible light

Answer 1

Shortest = violet
Longest = red

Question 2

What are the primary colours whose wavelengths are detected by cells in the retina

Answer 2

• Blue - short
• Green - medium
• Red - long

Question 3

By what attributes can a colour be defined

Answer 3

• Hue
• Value
• Chroma
• (Translucency?)

Question 4

What is the Hue of a colour

Answer 4

• ## This is the quality by which it is possible to distinguish one colour family from another

Question 5

What is the value of a colour

Answer 5

• An achromatic measure of the lightness or darkness of a particular colour, ranging from pure black to pure white
• Most important factor in colour determination

Question 6

What does it mean if a colour has a high or low shade

Answer 6

High value - light shade

Low value - dark shade

Question 7

What is the chroma of a colour

Answer 7

• This is the degree of strength or saturation of a colour of particular hue
• Describe the intensity or vividness of a colour

Question 8

What happens to light in translucent objects

Answer 8

• The light is permitted to pass through the object but is dispersed rather than absorbed or reflected

Question 9

AY BAWS CAN I HABE DE NOTE PLZ

Answer 9

Translucency is susceptible to changes with age

Question 10

What is the value contrast effect

Answer 10

Basically says that the relative lightness of an object is affected by the lightness of the contrasting background or surrounding i.e. looks lighter as background becomes darker

Question 11

What is the hue contrast effect

Answer 11

• When viewed against different background colours the teeth/object appears to take on the hue of the background’s complementary colour

Question 12

What is metamerism

Answer 12

This is the phenomenon where 2 objects can look the same colour under certain lighting conditions and different under other due to differing spectral analysis curves?

Question 13

What is opalescence

Answer 13

• Light scattering phenomenon caused by the presence of fine particles (opalisers)

Question 14

What is fluorescence

Answer 14

• Emission of visible light by an object when exposed to UV light

Question 15

AY BAWS CAN I HABE DE NOTE PLZ

Answer 15

Teeth exhibit a degree of fluorescence, opalescence and translucency

Question 16

How can maxillary anterior teeth differ in colour to mandibular anterior teeth

Answer 16

Maxillary anteriors can appear slightly more yellow than mandibular anteriors

Question 17

How can maxillary incisors differ in colour to lateral incisors and canines

Answer 17

Higher in value (lighter shade)

Question 18

How can the teeth of females differ to that of males

Answer 18

Slightly lighter (higher value) and less yellow than males

Question 19

What happens to the colour of teeth with age

Answer 19

• Teeth tend to become darker and more yellow

Question 20

What differences in colour can occur at the incised edge

Answer 20

• Often more translucent

- More affected by its background

Question 21

What differences in colour can affect the cervical region of teeth

Answer 21

• Colour is modified at the cervical region by the scattered light from the gingiva and is generally more saturated than incisal

Question 22

What can drying teeth do to the colour of them

Answer 22

• Make them look whiter

Question 23

What can be use to measure/compare tooth colours

Answer 23

Subjectively = shade guides
Objectively = spectrophotometers, colourimeters

Question 24

What 3 types of shade guide are there

Answer 24

• Vita Lumin
• Ivoclar chronoscope
• Vitapan 3D master system

Question 25

Give a brief description of the vita lumin shade guide and what aspect of colour it is based on

Answer 25

Based on hue with sub-classes of varying value and chroma

A = reddish-brown
B = orange-yellow
C = greenish-grey
D = reddish grey

Question 26

Give a brief description of the Ivoclar shade guide and what aspect of colour it is based on

Answer 26

Based on hue with sub classes of varying value and chroma

1 series = cream
2 series = orange
3 series = light brown
4 series = grey
5 series = dark brown

Question 27

Give a brief description of the vitapan 3D master system shade guide and what aspect of colour it is based on

Answer 27

Based on a simple but methodical approach based on 3 dimensions of colour, emphasising value as the most important dimension in colour matching

Question 28

What are some of the shortcomings of shade guides

Answer 28

• Restricted and inadequate range of shades
• Made from thick layers of high fusing porcelain and doesn’t allow for variations in thickness
• No surface texture or other characteristics
• Ceramic material used is different to restorative material so has different optical properties

Question 29

What should be done to make sure that the shade selection isn’t altered by external factors

Answer 29

• Select shade prior to tooth prep to remove factors like tooth drying
• Work under controlled lighting - natural light
• Remove brightly coloured make up

Question 30

How should you set out the vita shade tags

Answer 30

In order of decreasing value and not of hue

Question 31

What attributes of colour should be chosen in what order in the shade matching process

Answer 31

Value and then dominant chroma and hue

Question 32

What are the advantages of technology based shade matching

Answer 32

• No influence of surroundings
• No influence of lighting
• Reproducible results
• Improved communication between dentist and lab
• Integration with available hardware (digital camera, printer) and image enhancing software