2- Color and Shade Matching (Dr. Muftu)

- Esthetics

- Comfort

- Function

- Biologic health

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

- Color

- Translucency

- Texture

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

- Light source

- Object (Interaction of light and matter)

- Observer

The mechanism of visual color perception relies on (3)

around 400-700 nm

What is the visible light wavelength?

Color rending index (CRI)

Define the following:

Ability of a light source to reveal colors accurately compared to ideal or reference light source (i.e. N. daylight)

0-100

What is the scale for CRI?

FALSE

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

T/F: Lower CRI = better coloring rendering ability

They have the same color temperature

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

color temperature

What has the following characteristics?

- Refers to appearance of light emitted by a 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

Black body radiation

Color temperature is related to the color standard ___________

6500ºK (northern daylight)

What is the color temperature for northern daylight?

Incandescent light

What type of light?

- Emits a high concentration of yellow waves

- Not suitable for shade matching

- Low CRI

Fluorescent light

What type of light?

- Emits a high concentration of blue waves

- Not suitable for shade matching

- CRI of 50-80

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

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

What is the ideal light?

Close to 100

what is the CRI of natural daylight?

Yellow/orange, blue/green

Morning and evening daylight is rich in __________ and lacks _________

shorter wavelengths scatter before penetrating the atmosphere

Why do morning/evening daylight lack blue/green?

Hours around noon

What is the most ideal time of daylight for CRI?

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

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

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

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

5,500K and CRI 90

Standard illumniant for dentistry has a color temperature of ____K and CRI of _____

TRUE

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

a) opaque

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

a) opaque

b) translucent

c) transparent

c) transparent

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

a) opaque

b) translucent

c) transparent

b) translucent

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

a) opaque

b) translucent

c) transparent

TRUE

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

Material thickness

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

Specular reflection

Define the following:

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

- Creates a shiny appearance

Diffuse 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

Gloss

Define the following:

- "A view of material appearance"

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

- Ability of a surface to reflect light in a specular direction

Gloss

All of the following are factors that affect _____:

- Refractive index of material

- Angle of incident light

- Surface topography

- Rods

- Cones

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

Rods

What part of the eye?

- Peak sensitivity (490- 495nm)

- black /white

Cones

What part of the eye?

- Short, 420-440 nm

- Medium, 530-540 nm

- Long, 560-580nm

- blue-, green-, red- sensitive

True

T/F: Rods are monochromatic, cones are trichromatic

males 8% (females 0.5%)

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

Colorimeters

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

spectrophotometers

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

- Hard to measure vital teeth

- Hue

- Value

- Chroma

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

Munsell color system

(CIE 1976 color space)

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

hue

Define the following:

- Variety of color

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

There are a total of 10 hue gradations

In the munsell system, how many hues are there?

hue

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

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

chroma

Define the following:

Intensity or saturation of a hue

Less

low chroma = more or less color?

a) Very intense color

A high chroma is...

a) Very intense color

b) Very pale color

FALSE

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

value

What has the following characteristics?

- Relative darkness/lightness of a color aka brightness of object

- Amount of light energy an object reflect or transmits

value

What has the following characteristics?

- Amount of light energy an object reflects/transmits

- Objects of different hues/chroma can be identical value

Ranges from 5.5-8.5

What is the value for natural teeth?

true

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

TRUE

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

lightness

CIE color space expresses what with L*?

black

L* = zero, what color?

white

L* = 100, what color?

redness

CIE color space expresses what with positive a*?

greenness

CIE color space expresses what with negative a*?

-90 to 70 Δa*

a* has what numerical range?

yellowness

CIE color space expresses what with positive b*?

blueness

CIE color space expresses what with negative b*?

-80 to 100 Δb*

b* has what numerical range?

color difference

This is the equation for what?

b. does NOT consider color modifiers

Which of the following is false regarding shortcomings of CIE?

a. mathematically accurate but not practical for dentistry

b. considers color modifiers

c. does not consider optical phenomena

Fluorescence

Define the following:

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

FALSE - should say VITAL

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

b) dentin

The fluorescent effect of teeth come from __________

a) enamel

b) dentin

c) pulp

Dentin

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

b) the more dentin fluoresces, the lower the chroma

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

TRUE

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

Check optical interaction with black light

How do you check for fluorescence of teeth or restorations?

Opalescence

Define the following:

Property of transparent or translucent materials which gives those materials a milky appearance, with iridescent reflections that resemble opal stone

a) enamel

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

a) enamel

b) dentin

c) pulp

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

- this is why the enamel can be viewed as having a blue-ish white color

which of the following statements is true?

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

blue ish white

incisal enamel can be viewed as having a ____ color

counter opalescence

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

Metamerism

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 _________

intrinsic and extrinsic colorimetric effects

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

reflection, absorption

Intrinsic colorimetric effects is associated with ___________ and ___________ of light

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

What are extrinsic colorimetric effects associated with?

Bluish

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

b) dentin

Tooth color is mainly determined by the color of __________

a) enamel

b) dentin

c) pulp

70% light

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

not much more than 30%

Dentin transmits _____% light through a 1mm thick section

True

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

Yellow

Maxillary anterior teeth are slightly more ________ than mandibular anterior teeth

all of the above are true

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

Shade selection

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

Vita

What is the shade guide we use at tufts?

C, B, A, D

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

hue-oriented

Is this hue-oriented or value-oriented?

value-oriented

Is this hue-oriented or value-oriented?

value-oriented

What type of shade guide is recommended: Hue-oriented or value-oriented?

A) Beginning of appointment

When should the shade comparisons be performed?

A) Beginning of appointment

B) End of appointment

C) Immediately after prep is done

d - evaluate shade under multiple lights

principles of shade selection include all the following except:

a) teeth must be clean

b) remove bright colors from FOV

c) view pt at eye level

d) evaluate shade under the brightest light

e) make shade comparisons at the beginning of appt

f) shade comparisons should be made quickly to avoid eye fatigue

g) select before dehydration (before prep and rubber dam placement)

25-35cm

What is the ideal distance for shade selection?

Commercial Shade Guides

What has the following characteristics?

- Most convenient and common method of making shade selections

- Guides consist of shade tabs

- - Metal backing

- - Opaque porcelain

- Neck, body, and incisal color

- Select tab with the most natural intraoral appearance

Whitish-yellowish and slightly reddish, and light

Teeth are predominantly what colors?

Extended range shade guides

What has the following characteristics?

- Most shade guides do not cover all the colors in the natural dentition

- Some porcelain systems extend the typical range

- - Bleached shades

- - Dentin shades

- - Custom shade guides

Material specific shade guides

What has the following characteristics?

i.e. for e.max (lithium disilicate)

- High translucency

- Low translucency

- Medium translucency

- Medium opacity