colour matching

Question 1

Which 3 things may influence colour perception?

Answer 1

1. light source
2. object
3. observer

Question 2

Hue

Answer 2

• the change in colour
• colour identified by a specific wavelength
  the rainbow

Question 3

Value

Answer 3

• lightness from white to black
• high value = white
• low value = black
• different values in between = grey

Question 4

Chroma

Answer 4

• the strength/purity of the colour
• change in colour from grey to a pure colour

Question 5

Colour Difference

Answer 5

• measures the difference between 2 points in the colour space.
• allows machines to differentiate between 2 colours and give a value.
• 1 and below - hard for people to distinguish between.
• 3.7 and above - noticeable difference.

Question 6

Factors impacting the colour of the final restoration:

Answer 6

1. light
2. layers
3. technician
4. observer
5. shade guide
6. porcelain
7. preparation
8. restoration type

Question 7

Problems from objects which alter colour perception.

Answer 7

• different colours across the whole surface
• dry vs wet
• size; makes it difficult due to eye fatigue
• curvature; difficult to match due to reflection and highlights

Question 8

On shade guides, what do the A, B, C and D groups represent?

Answer 8

different hues

Question 9

As the number increases from A1-4, what does this represent?

Answer 9

The chroma increases and value decreases.

Question 10

Guidelines for Colour Matching

Answer 10

1. make the shade selection at the beginning of the appointment (before crown prep and imps)
2. look at a neutral background
3. use different light sources (surgery light, daylight etc)
4. If tooth shade is difficult, take a photo, call a technician or if available, use shade matching instrument.

Question 11

Name 3 colour marching instruments.

Answer 11

1. spectrophotometers
2. colorimeters
3. intraoral matching instruments