11. edited from ryanef123 quizlet: 11 - Color and Shade Matching (Dr. Muftu)

What are the parameters under which we should enhance or maintain quality of life for craniofacial function?

- Esthetics

- Comfort

- Function

- Biologic health

What are the three main features in a natural tooth that must be produced in dental porcelain or an esthetic restorative material are?

- Color

- Translucency

- Texture

The mechanism of visual color perception relies on (3)

- Light source

- Object (Interaction of light and matter)

- Observer

nature of color depends on

nature of light + interaction of light and material → subjective experience/observer: human eye or instrument

What is the visible light wavelength?

around 400-700 nm (350-750)

Define the following:

• from lecture ability of a light source to reveal colors accurately compared to ideal or reference light source (i.e. N. daylight)

• measures how accurately a light source reveals the true colors of objects compared to natural sunlight, on a scale from 0–100

  • higher CRI (90+) ensures vibrant, accurate colors

  • lower CRI (<80) makes colors appear muted or distorted

Color rending index (CRI)

What is the scale for CRI?

0-100 (90 is good for us)

T/F: Lower CRI = better coloring rendering ability

FALSE

Higher CRI = better coloring rendering ability; 100 = perfect match

CRI measures for a pair of light sources can only be compared if __________

They have the same color temperature

What has the following characteristics?

• description of the warmth or coolness of light source

• Helps define whether light looks warm (yellowish), neutral, or cool (bluish)

• Related to the color standard black body radiation

• Reported in degrees Kelvin

color temperature

Color temperature is related to the color standard ___________

Black body radiation

definition: color changes with temperature, moving from red to orange, yellow, white, and finally blue-white as it gets hotter

• higher temperatures emit light at shorter wavelengths vs low-temperature objects appear red or dim, while hotter objects (like stars) appear bright white or blue-white

black body radiation

What is the color temperature for northern daylight?

6500ºK (northern daylight)

color temp of red, yellow, white, northern daylight, pale blue

• 1000K – red

• 2000K – yellow

• 5555K – white

• 6500K – northern daylight

• 8000K – pale blue

Most of the lightbulbs we see give off incandescent light. which of the following is true?

a) Emits a high concentration of yellow waves

b) Suitable for shade matching

c) High CRI

a) Emits a high concentration of yellow waves (others are opposite)

which of the following is true about fluorescent light?

a) emits a high concentration of red waves

b) suitable for shade matching

c) CRI of 50-80

c) CRI of 50-80 (high concentration of blue waves, not suitable)

What is the ideal light?

northern daylight considered best as it is closest to emitting the full spectrum of white light CRI ~100

- specifically hours around noon, where full spectrum of colors visible

what is the CRI of natural daylight?

Close to 100

Morning and evening daylight is rich in __________ and lacks _________

Yellow/orange, blue/green

Why do morning/evening daylight lack blue/green?

shorter wavelengths scatter before penetrating the atmosphere

What is the most ideal time of daylight for CRI?

Hours around noon

Why are hours around noon the most ideal time of daylight for CRI?

incident daylight most visible light spectrum, full spectrum of colors visible

Standard illuminant for dentistry, D55, is defined as what?

Washington DC, June, 12-1pm, with a slight overcast, color temp of 5,500K and CRI 90

Standard illuminant for dentistry has a color temperature of ____K and CRI of _____ (!)

5,500K and CRI 90

T/F: When light strikes an object, the color that we see is what is left of the spectrum after part of it is absorbed by the object. So for example, a red object looks red bc it reflects red more than green or blue

TRUE

when light strikes an object the reaction depends on what four things?

whether object is transparent, translucent, rough, opaque

If all the light reflects back, then it is considered:

a) opaque

b) translucent

c) transparent

a) opaque

If all the light passes through, then it is considered:

a) opaque

b) translucent

c) transparent

c) transparent

If some of the light is refracted at different angles, including bouncing back, then it is considered:

a) opaque

b) translucent

c) transparent

c) translucent

T/F: The more glass you have the more translucent the material is. The more crystals, the stronger but more opaque it is

TRUE

For each preparation, we must determine the required amount of tooth reduction and carefully select the restorative material, as translucency is also influenced by ___________

Material thickness

“view of material appearance”

gloss

• An optical property based on the interaction of light with physical characteristics of a surface

• Ability of a surface to reflect light into the specular direction

gloss

what three factors affect gloss?

• the refractive index of the material

• the angle of incident light

• the surface topography

Define the following:

- A reflection produced by a smooth surface in which parallel light rays are reflected in parallel

- Creates a shiny appearance

Specular reflection

Define the following:

- Reflection that occurs when parallel rays of light hit a rough surface and all reflect at different angles

- Creates a matte appearance

Diffuse reflection

The retina is made up of what two types of photoreceptor cells?

- Rods

- Cones

What part of the eye?

- Peak sensitivity (490- 495nm)

- black /white

Rods

What part of the eye?

- Short, 420-440 nm

- Medium, 530-540 nm

- Long, 560-580nm

- blue-, green-, red- sensitive

Cones

T/F: Rods are monochromatic, cones are trichromatic

True

A defect in color vision is more common in what gender?

males 8% (females 0.5%)

ID THE DEVICE:

• Analyze the values for red, green and blue reflected through filters that simulate sensing photoreceptor cells of the human eye

• "Reliable enough"

• The tristimulus X, Y and Z coordinates are automatically converted to L*, a*, b* value

• Less expensive

• Easy to use chairside; more practical

Colorimeters

ID the device:

• Measure and record the amount of light reflected or transmitted from the object through its wavelength

• High precision, sensitivity to measure absolute colors and are equipped with spectral distributions of various illuminants

• Complex and expensive; investigative not practical

• Hard to measure vital teeth

spectrophotometers

Color space specifies colors based on 3 color dimensions. What are they?

- Hue

- Value

- Chroma

What color system do we use to communicate and compare color?

Munsell color system

(CIE 1976 color space)

Define the following:

- Variety of color

hue

In the munsell system, how many hues are there?

• 5 principal: Red, Yellow, Green, Blue, Purple

• 5 intermediate

• each of these are then broken into 10 substeps totaling 100 hues, each given integer values

What has the following characteristics according to the munsell color theory?

- Determined by reflected wavelength of observed light within the visual light spectrum (VLS)

hue

Define the following:

Intensity or saturation of a hue (how red is the red)

chroma

low chroma = more or less color?

Less

A high chroma is...

a) Very intense color

b) Very pale color

a) Very intense color

T/F objects of different chroma and value can be of identical hue

FALSE

What has the following characteristics?

• Relative darkness/lightness of a color aka brightness of object; sum of light that returns from target tooth to the eyes)

• Amount of light energy an object reflect or transmits

value

Objects of different hues/chroma can be identical (BLANK)

value

What is the value for natural teeth?

Ranges from 5.5-8.5

T/F: Restorations too high in value are easily detected

true

black vs white value

T/F: Objects of different chroma and hue can be of identical value

TRUE

CIE color space expresses what with L*?

lightness

L* = zero, what color?

black

L* = 100, what color?

white

CIE color space expresses what with positive a*?

redness

CIE color space expresses what with negative a*?

greenness

a* has what numerical range?

-90 to 70 Δa*

CIE color space expresses what with positive b*?

yellowness

CIE color space expresses what with negative b*?

blueness

b* has what numerical range?

-80 to 100 Δb*

This is the equation for what?

color difference

Which of the following is true regarding shortcomings of CIE?

a. mathematically accurate but not practical for dentistry

b. considers color modifiers

c. does not consider optical phenomena

b. does not consider color modifiers

Define the following:

Absorption of light by a material and the spontaneous emission of light in a longer wavelength

Fluorescence

fluorescent substances absorb the UV light and then re-emit it almost instantaneously

true

what makes an object appear to glow (fluorescence)

some E lost in process of absorbing UV light so the emitted light has a longer wavelength then the absorbed radiation which make the light visible and therefore material ‘glows’

T/F: Non-vital teeth look brighter and alive because higher amount of organic material is present

False, *vital

When natural teeth are exposed to ultraviolet (UV) light, fluorescence is observed, with an emission spectrum band ranging from white to intense blue light with a wavelength shorter than 400nm

true

The fluorescent effect of teeth come from __________

a) enamel

b) dentin

c) pulp

b) dentin

______ contains a greater amount of UV photosensitive organic pigment than enamel and is 3x more fluorescent

Dentin

Which of the following is true?

a) the more dentin fluoresces, the higher the chroma

b) the more dentin fluoresces, the lower the chroma

c) the more dentin fluoresces, the higher the value

d) the more dentin fluoresces, the lower the value

b) the more dentin fluoresces, the lower the chroma

T/F: Ceramics that lack a fluorescent agent appear as missing teeth when viewed in the dark

TRUE

How do you check for fluorescence of teeth or restorations?

Check optical interaction with black light

Define the following:

Property of transparent or translucent materials which gives those materials a milky appearance, with iridescent reflections that resemble opal stone; material one color when light reflected and other color when light transmitted

Opalescence

the opalescence of teeth can be attributed to which layer of the tooth?

a) enamel

b) dentin

c) pulp

a) enamel

which of the following statements is true: reason why enamel seems blue-ish white

a) enamel acts as a filter & selectively forwards long waves, and reflects short waves

b) enamel acts as a filter & selectively forwards short waves, and reflects long waves

c) enamel does not forward/reflect waves, dentin does

a) enamel selectively forwards long waves, and reflects short waves

incisal enamel can be viewed as having a ____ color

blue ish white

dentin will reflect long waves too, giving enamel an orange glaze. what is this effect known as?

counter opalescence

Define the following:

The color of a pair of specimens having different spectral reflectance functions matches under one set of illuminant and observer conditions but mismatches under another set of conditions

Metamerism

Two colors that appear to be a match under a given lighting condition but have different spectral reflectance = metamers. The phenomenon is _________

Metamerism

the color of a tooth is determined by a combination of __________ and __________ effects

intrinsic and extrinsic colorimetric effects

Intrinsic colorimetric effects is associated with ___________ (2)

reflection and absorption of light

extrinsic colorimetric effects is associated with _____________

coloring materials interacting with enamel, such as coffee, tea, tobacco

Enamel plays a minor role scattering at wavelengths at the _________ range

Bluish

Tooth color is mainly determined by the color of __________

a) enamel

b) dentin

c) pulp

b) dentin

Enamel transmits about ______% light through a 1mm thick section

70% light

Dentin transmits _____% light through a 1mm thick section

not much more than 30%

T/F: Color transitions from cervical to incisal, mesial to distal, labial to lingual. they vary in thickness of enamel/dentin and in translucency/opacity of enamel/dentin

True

Maxillary anterior teeth are slightly more ________ than mandibular anterior teeth

Yellow

All of the following are true except?

a) Maxillary central incisors are higher in value than maxillary lateral incisors and canines

b) No significant difference between color of male and female teeth

c) With age, teeth have lower value (darker) and get more yellow - decreased E and increased D

all of the above are true

__________ is a subjective evaluation with considerable variation. Subtle variations can exist without causing disharmony in smile

Shade selection

What is the shade guide we use at tufts?

Vita

What is the order of recommended sequence for the Vita classical shade guide?

A) Value selection

B) Chroma selection

C) Hue selection

D) Final Check/Revision

C, B, A, D

Is this hue-oriented or value-oriented?

hue-oriented