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Fixed Prosthodontics > Midterm - Spring > Flashcards

Midterm - Spring Flashcards

1
Q

What are the two main types of color systems?

A

Munsell and CIELAB.
Munsell has Hue (actual color), Chroma (intensity of the color), and Value (the brightness, has more to do with how light interacts with it, the amount of light or dark in it)
CIELAB consists of a, b, and L* (achromatic characteristics while the other two are chromatic)
- Both of these describe color in three dimensions.

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2
Q

What is Hue determined by?

A

By the wavelength of the reflected and/or transmitted light observed
- Longer wavelength = red range
- Shorter wavelength = violet range
ROYGBIV
-Red has longer wavelength, lower frequency, lower energy
-Violet has shorter wavelength, higher frequency, higher energy

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3
Q

What is chroma?

A

It is the intensity of the hue, the amount of saturation, the strength of a given hue, the concentration of pigment

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4
Q

What is value?

A

Adds component of light, relative lightness or darkness of a hue. The brightness. It is a consequence of the amount of light energy reflected or transmitted by the object. It is a consequence of how transmitted or reflected light is influenced by the object.

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5
Q

If two objects have identical hue and chroma, but different values, the one with the higher value will appear lighter or darker?

A

Lighter

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6
Q

Porcelain shades with higher values are often mistaken to have a high or low chroma?

A

Low chroma

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7
Q

A common problem in metal-ceramic restorations is a value that is too high or too low?

A

Too high. The hue and chroma may be accurate, but if the opaque layer of porcelain reflects too much light, the tooth appears “bright.” The value is too high.

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8
Q

In the CIELAB system, what do a, b, and L* correspond to?

A

a* and b* define a hue and a chroma. L* corresponds to the value.

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9
Q

What are the four main factors that affect our ability to correctly determine shade with our eyes?

A
  1. The influence of surrounding colors (-Assistant clothes that have a lower chroma, in the pastel range, are more relaxing and will help shade matching instead of hurting. The extremes are what you want to avoid)
  2. Color adaption by our eyes
  3. Metamerism (-This is how light can make the same object look a different color)
  4. Color blindness
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10
Q

What are the characteristics of color adaptation?

A
  1. Color vision decreases rapidly as a person stares at an object
  2. The original color appears to become less and less saturated until it looks almost gray
  3. Between comparisons, rest eyes by glancing at a gray object
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11
Q

What is the definition of metamerism?

A

The phenomenon of two colors that match under one set of conditions, but fail to match under a different set

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12
Q

What are the two different ways that yellow can be yellow?

A
  1. By reflecting yellow and absorbing all other colors

2. By reflecting orange and green (which when combined make yellow) and absorbing all other colors

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13
Q

How can a clinical diminish the effect of metamerism?

A

By confirming shades in different lighting conditions

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14
Q

What are the characteristics of color blindness?

A

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

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15
Q

What is opalescence?

A

A translucent bluish-white appearance
Characteristic of natural enamel
Most noticeable on the incisal edges of anterior teeth
Created as light passes through and is scattered by enamel

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16
Q

Shade matching is entirely a subjective process. True or False?

A

True

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17
Q

The human eye is a good light meter. True or False?

A

False, but the human eye is good at discriminating relative differences

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18
Q

Which is the most important factor in the treatment room, hue, chroma, or value?

A

Chroma. You don’t want a Munsell chroma of more than 4 (pastels) in room, clothing, patient napkin, etc. No complimentary, bright colors near mouth

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19
Q

What does the ceiling mostly do to light and color and what should the value be in a treatment room ceiling?

A

Ceiling is mostly a reflector and should have a high value of 9 or more

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20
Q

When complimentary colors are in close proximity to a color, it will make the chroma seem higher or lower?

A

Higher

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21
Q

What are the different hues that teeth contain?

A

Yellow, orange, red, and blue

22
Q

What are the primary colors? Secondary colors?

A

Red, yellow, and blue.

Orange, purple, and green.

23
Q

What are the complimentary color matches?

A

Red and Green
Orange and Blue
Yellow and Purple

24
Q

What lipstick colors could interfere the most with your shade matching?

A

Purple, blue, green, orange

25
Q

It is best to have patient remove lipstick when shade matching. True or False?

A

True

26
Q

What is considered to be the true color temperature as perceived by humans?

A

D65.

2500 Kelvin = D25, 5500 Kelvin = D55

27
Q

What color temperature range is best for shade matching?

A

D50 to D65

28
Q

What is the color rendering index (CRI)?

A

It is a 1 to 100 scale that measures how well a particular light source renders color

29
Q

What CRI is best for shade matching?

A

CRI 91 - 98

30
Q

What is the true goal of shade matching?

A

To end up close enough that the human eye cannot differentiate between the two. We will never get it exactly.

31
Q

What do the letters and numbers stand for with the VITA classical shade guide?

A

Each letter is a different hue and each number is a different chroma

32
Q

When you look at two different tabs and squint, the one that disappears last is the higher or lower value?

A

Higher

33
Q

What are the keys to using VITA classical shade guide to determine value?

A

■ Use shade guide with shades arranged by value.
■ Observe from a distance.
■ View by squinting eyes to block out excessive light. Photopic to Scotopic vision…
■ The object that disappears from sight first is the object with the lower value.
■ Choose the shade tab that fades from sight at the same time that the tooth fades from sight as you are squinting.
■ Now, compare the value of this shade tab to the value of the shade tab selected for hue and chroma.
■ If the value determination shade tab has a 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.
■ If the value determination shade tab has a higher value (lighter) than the shade tab selected by hue and chroma, you should choose a different shade with higher value because you cannot add value by staining.

34
Q

If you are going to err with value, should you err lighter or darker?

A

Err lighter with a higher value, because it will be easier for the lab to bring it down, make it darker, and get it close. You cannot add value by staining.

35
Q

What are the main summary points for shade matching?

A

■ Teeth to be matched should be clean.
■ Shade matching should be accomplished at the beginning of the visit. A desiccated tooth increases its value.
■ If the tooth and shade tab have differing surface textures, wetting the surface of both helps to remove the differences.
■ Cheek retractors are helpful to create an unobstructed view of the area.
■ As a help in determining hue, remember that the cervical area of the unrestored canine has the highest chroma of the dominant hue.
■ Shade should be observed in multiple ambient conditions. And, on more than one occasion.
■ Use color corrected lights in treatment rooms where shades are most commonly taken.
■ View shade comparisons at a distance of about 10” to 12
■ View directly for hue and chroma selection
Cones are more concentrated in center of retina.
■ View peripherally while squinting for value selection.
Rods are more concentrated on periphery of retina.
Squinting diminishes input from cones.
■ First impression is usually the most correct one (Cones begin to fatigue within 5 – 7 seconds.)
■ Between comparisons, glancing at a gray object rests the operator’s eyes and helps avoid retinal cone fatigue.
■ Utilize multiple sets of eyes, especially female eyes.
■ Get your ceramist involved.
■ Utilize photography
■ Map the polychromatic nature of the tooth/teeth. (cracks, hypo-calcification areas, translucencies, etc…)

36
Q

Where in the eye are cones and rods more concentrated?

A

Cones are in center of retina and rods are on periphery of retina. So view directly for hue and chroma, and view peripherally while squinting for value selection. Squinting diminishes input from cones.

37
Q

What is scotopic vision?

A

Scotopic vision is the vision of the eye under low light conditions. In the human eye, cone cells are nonfunctional in low light – scotopic vision is produced exclusively through rod cells which are most sensitive to wavelengths of light around 498 nm (green-blue) and are insensitive to wavelengths longer than about 640 nm (red).

38
Q

What is photopic vision?

A

Photopic vision is the vision of the eye under well-lit conditions. In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher visual acuity and temporal resolution than available with scotopic vision.

39
Q

What are the indications for veneers?

A
  • Minor morphological changes
  • Moderate morphological changes
  • Moderate shade changes (not minor, do bleaching first)
40
Q

What are contraindications for veneers?

A
  • Insufficient tooth structure
  • Insufficient enamel for bonding
    (All enamel is best, three enamel surface is good, and TWO enamel surface is the absolute minimum for maxillary anteriors, but try and avoid, and if you do, do full coverage jacket, and he says that THREE CAVOSURFACE MARGINS WITH ENAMEL is the minimum for everything else
  • Poor oral hygiene
  • Uncontrolled periodontal disease
  • Uncontrolled caries
  • Parafunctional habits
41
Q

What are the downsides to “no prep” veneers?

A

Not sure where it goes because there is no prep. Bulky and difficult to clean gingival margin, over contoured toward labial. Patient’s lip feels tight, enlarges teeth, can retrude or distalize mandible and create TMJ problems.

42
Q

What are the main types of veneer preparations?

A
  1. No prep veneers
  2. Light preparation (most common)
  3. Heavy preparation (wrap around, reverse 3/4 crown)
    - -You save the lingual surface of the tooth. For lower incisors, he hates full coverage crowns. He would do this on lower incisors.
43
Q

What are the different margin finishes for veneers?

A 
Facial only
- Butt margin (anterior only)
- Chamfer margin 
- Feathered margin (posterior only)
Facial + incisal
- Lingual butt margin
- Lingual chamfer margin
Lingual veneer
44
Q

Why would you ever do a lingual veneer?

A

To recreate cuspid guidance

45
Q

What are the indications for a light preparation for a veneer?

A
  • Minor Morphological Changes
  • Moderate Morphological Changes
  • Moderate Shade Changes
  • Four Incisal Designs
    Facial Butt Margin
    Facial Chamfered Margin
    Lingual Butt Margin
    Lingual Chamfered Margin
46
Q

What type of margin finish would you not want to do on the mandibular incisors?

A

-You don’t want to do a facial butt margin on the mandibular incisors because that is where the incisors occlude

47
Q

What are the indications for a heavy preparation for a veneer?

A 
More Significant Morphological Changes
More Significant Shade Changes
Deeper Chamfer and Complete Interproximal & Incisal Preparation
Two Incisal Designs
- Lingual Butt Margin
- Lingual Chamfered Margin
Consider Full-Coverage
48
Q

What are the main materials for veneers?

A

Feldspathic porcelain and lithium disilicate

49
Q

What are the three requirements for veneers to be placed over existing restorations?

A
  1. In excellent condition
  2. Small in size
  3. Not discolored
    Can be put over class I, II (caution), III, IV, and V
50
Q

What are the measurements of the 6878K-018 diamond and the 5856-016 diamond at the tip, at the shank, and overall length?

A

018
Tip = 1.2 mm
Shank = 1.9 mm
Length = 8.0 mm in length

016
Tip = 1.0 mm
Half-way = 1.25 mm
Shank = 1.5 mm

51
Q

If an exact match cannot be selected, a shade tab with the lower chroma and highest value should be selected, because extrinsic characterization can be used to increase chroma and reduce the value. True or False?

A

True

Fixed Prosthodontics (8 decks)

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