shade matching Flashcards
1
Q
What is part of the Munsell Color System?
A
Hue
Chroma
Value
2
Q
what is par of the CIELAB color system?
A
a*
b*
L*
3
Q
How are the Munsell and CIELAB systems similar?
A
both describe color in three dimensions
4
Q
What are chromatic characteristics?
A
Hue: color, distinguishes one color from another
Chroma: intensity (strength or weakness) of that color
A & B: color (hue) and intensity (chroma)
5
Q
What are achromatic characteristics?
A
Value: brightness, how light interacts with color. indicates the lightness or darkness of the color
L: value, not related directly to color itself. related to brightness. relative lightness or darkness
6
Q
What cause the most trouble with crowns out of Hue, CHroma, and Value?
A
Value
7
Q
As chroma decreases in the Munsell system the hue becomes ______?
A
more similar
8
Q
In what direction is chroma in the munsell color system?
A
inward and outward
9
Q
in what direction is value in the munsell color system?
A
circumferential
10
Q
In what direction is the value in the munsell color system?
A
up and down (white–> grey –> black)
- yellow, green/yellow, green, blue/green. blue
- yellow/red, red, red/purple, purple, purple blue
11
Q
What numbers does value go through?
A
1, black - 9, white
12
Q
what numbers does chroma go through>?
A
1 less intense, 12 more intense
13
Q
an increase in value is an increase in ___?
A
brightness
14
Q
what equal the hue diagram?
A
Value scale + Chroma scale
15
Q
Hue
A
- determined by wavelength of the REFLECTED and/or transmitted light OBSERVED
- shorter wavelength = violet
- longer wavelength = red
16
Q
shorter wavelengths have ______ frequency and ______ energy
A
higher, higher
17
Q
longer wavelengths have ________ frequency and ________ energy
A
lower, lower
18
Q
What is the order of the elctromagnetic spectrum?
A
gamma, xray, UV, visible, infrared, microwave, radio
19
Q
Chroma
A
Intensity of the hue
Saturation
Strength of a given hue
concentration of pigment
20
Q
T/F blue and green can reflect the same amount of light energy?
A
True
21
Q
Value
A
- adds component of light
- relative lightness or darnkess of a hue
- Brightness
- a consequence of the amount of light energy reflected or transmitted by the object
- a consequence of how transmitted or reflected light is influenced by the object
- how does the object interact with the influence light
22
Q
T/F porcelain shades with higher values are often mistaken to have a low chroma
A
True
23
Q
T/F just because something is bright (has a higher value) it does not mean that the object is more WHITE
A
True
24
Q
What are the 4 factors affecting our ability to correctly determine Shade with our eyes?
A
- influence of surrounding colors
- color adaptation by our eyes (eyes begin to fatigue, look at a pastel then go back to shade matching)
- Metamerism (how light makes us percieve the color, exact same object in two different lights looks like 2 different colors)
- Color Blindness
25
Pastel shades have ___ chroma
low
26
T/F bright white can make it difficult to shade match
True
27
What is color adaptation?
- color vision decreases rapidly as a person stares at an object
- the original color appears to become less and less saturated until it looks almost gray
- between comparisons, rest eyes by glancing at a GRAY object
28
What is metamerism?
the phenomenon of two colors that match under one set of conditions, but fail to match under a different set
29
How can metamerism occur?
reflects color that seeing or a combination of colors that make up the colors that seeing: different light spectra will act on both objects differently, resulting different appearing colors
ex. reflect yellow and absorb all other colors OR reflect orange and green and absorb all other colors
30
What type of stone demonstrates metamerism?
Alexandrite
31
How do you diminish the effect of metamerism?
by confirming shades in different lighting conditions
32
Color Blindness?
- Different types and degrees exist
- affects about 8% of the male population
- fewer females with any degree of color blindness
- Males: good idea to get a second opinion from a female
33
Opalescence
- a translucent bluish-white appearance
- characteristic of natural enamel
- most noticeable on the INCISAL EDGE of ANTERIOR TEETH
- created as light passes through and is scattered by enamel
34
T/F too much whitening can cause the patient to have blue looking teeth
True (ex. ultradent whitening)
35
5 points of Shade Matching
1. a SUBJECTIVE process b/c eye is good at discriminating relative differences. NOT a good LIGHT METER
2. beware of color adaptation by your eyes
3. confirm your choice in different lighting conditions
4. if you are male, ask for the input of a female
5. take measures not to be adversely influenced by environment
36
Shade matching environment
1. light is being reflected and scattered around the room
2. chroma is MOST IMPORTANT factor in tx room --> do NOT have munsell chroma of no more than 4 (pastels!)
3. ceiling is mostly a reflector and should have a high VALUE (9 or more)
4. clothing for dr, assistant and patient should be munsell chroma of 4 or less (pastel range)
5. patient napkin have munsell chroma of 4 or less
6. no bright, complimentary colors near mouth
7. lighting
37
Why don't want complimentary colors near each other?
in close proximity will make the chroma seem HIGHER
38
What are complimentary colors?
colors on opposite sides of the color wheel
39
```
Lipstick colors to avoid?
Yellow
Orange
Red
Blue
```
Purple
Blue
Green
Orange
40
Should a patient leave on lipstick for shade matching?
NO
41
What is light temperature measured in?
degree K
42
what is considered to be the true color temperature as perceived by humans?
D65 (6500 K)
43
What temperature range is best for shade matching?
D50-D65
44
What is the color rendering index? CRI
measures how well a particular light source renders color on scale of 1-100
45
What is the best CRI for shade matching?
CRI 91-98
46
T/F it is possible to get color replication EXACTLY?
F
47
What is the goal of color replication process?
to end up close enough that the human eye cannot differentiate between the two
48
What are the 2 phases in the color replication process?
Shade matching phase
| Shade duplication phase
49
What are the steps in the shade matching phase?
1. tooth/restoration
| 2. visual shade selection OR instrumental analysis
50
What are the steps in shade duplication phase?
1. corresponding porcelain OR porcelain mixing
1. surface characterization
2. porcelain crown
51
What are the two guides used for Shade Matching?
1. VITA Classical Shade Guide
| 2. VITA 3D-Master Shade Guide
52
Which shade guide is more accurate?
3D shades
53
What are 3 types of 3D master shade guide?
1. linearguide
2. bleachedguide
3. toothguide with bleached shades
54
How is the VITA classical shade guide organized?
```
into hues by letter and chroma by numbers
A- Red/brown 1-5
B- Red/yellow 1-4
C. Grey 1-4
D. Red/grey 1-3
```
OR can be organized by value *lightness
55
Using VITA classical for selecting VALUE
1. use the shade guide with shades arranged by VALUE
2. observe from distance
3. view by squinting eyes to block out excessive light (photopic and scotopic vision)
4. the object that disappears from sight FIRST is the object with the LOWER VALUE
5. choose the shade tab that fades from sight at the same time that the tooth fades from sight as you are squinting --> GIVES YOU CORRECT VALUE!
6. compare value of this shade tab to value of shade tab for hue/chroma
7. if value determination shade tab has LOWER VALUE (darker) than the shade tab selected by hue and chroma, the lab may have to decrease the value of the chosen shade (by hue and chroma) by either internal or external staining
8. if value determination shade tab has a HIGHER value (lighter) than the shade tab selected by the hue and chroma, you should choose a different shade with high value because YOU CANNOT ADD VALUE BY STAINING!
56
T/F it is harder to increase the value and brighten the tooth
True
57
In what order do you select shade in VITA classical?
1. hue 2. chroma 3. value
58
In what order do you select shade in VITA master 3d?
1. value 2. chroma 3. Hue
59
What is a benefit to VITA master SD?
more shades
60
What are other ways to match shade?
1. individuall diagram on a tooth (9 main sections)
2. hold incisal edge to incisal edge to show shade guide- hold two closest shades and photograph to send to the lab
3. custom shade tabs
4. stump preps
61
For Critical Shades...
1. clean teeth
2. shade matching at beg. of the visit! (a desiccated tooth increases its value!)
3. wet both surfaces of tooth and shade tab to remove surface texture differences
4. use cheek retractors for unobstructed view of area
5. to help find hue, cervical area of unrestored canine has the HIGHEST CHROMA of the dominant hue
6. shade should be observed in multiple ambient conditions on more than one occasion
7. use color corrected lights in treatment rooms where shades are most commonly taken
62
how far away should shade comparisons be taken?
distance of 10-12 inches
63
Why should hue and chroma be viewed directly?
because cones are more concentrated in center of eye
64
Why should Value be view peripherally while squinting?
because rods are more concentrated on periphery of retina and squinting diminishes input from cones
65
Why are first impressions usually most correct ones?
cones begin to fatigue in 5-7 seconds
66
How can the operator rest their eyes and avoid retinal cone fatigue?
between comparisons, glance at a gray object
67
T/F utilize one set of eye, especially male
FALSE, use MULTIPLE sets of eyes and especially females!
68
who is a key person to involve?
Ceramist
69
T/F photography can assist in getting critical shades?
True
70
What can be mapped on the tooth to aid in critical shades?
map the polychromatic nature of the tooth/teeth: cracks, hypo-calcification areas, translucencies etc.
71
What is shade duplicating?
1. complex
2. art
3. science
4. internal shading
5. external shading
6. translucencies
7. opacities
8. job for great ceramists! aka ANDY!
