the science of color, light and shade - student copy

5/26/2018 The Science of Color, Light and Shade - Student Copy

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The Science of Color, Light

and Shade SelectionPresented byLisa Fedor James D.D.S.


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Outline

Light and Color Description of Light

Quality of light

Description of Color

Hue, Chroma, Value Munsell Color System

Factors influencing perception

The eye (rods and cones)

Deceptive color perception Color Blindness

Shade selection

Techniques for determining shade / Shade guides

Shade mapping


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Visible electromagnetic energy whose

wavelength is measured in nanometers (nm)


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Without Light Color Does Not ExistWithout Light Color Does Not Exist

A yellow object

absorbs all

lightwaves of all

colors, but

reflects yellow


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Color

Influenced by three main factors

1. Physical properties of the object

2. Assessment of the observer3. Nature of incident light

Relationship to other colored objects


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LightPart of the electromagnetic spectrum

The eye is only sensitive to the visibleportion

of the spectrum (380750nm)

Different wavelengths constitute the different

colors we perceive


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Relatively equal quantities of electromagneticenergy over the VLS

When passed through a prism we see component

colors of white light Shorter

wavelengths bend

more than longer

wavelengths

Pure White Light

380nm

750nm

+ + + + + + =


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Quality of Light / 3 Types

1. Incandescent Light

2. Fluorescent Light

3. Natural Daylight

Most dental offices are outfitted with incandescent

and fluorescent lights


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1. Incandescent Light

Emits high concentration of yellow waves

Not suitable for shade matching

Low Color Rendering Index (CRI)


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2. Fluorescent Light

Emits high concentration of blue waves

Not suitable for shade matching

CRI =(50-80)


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3. Natural Daylight

Northern daylight considered the best Closest to emitting the full spectrum of

white light

Used as the standard by which to judgeother light sources

CRI close to 100


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Color Rendering Index

CRI = (0-100)

Indicates how well a light source renders color as

compared to a standard source (N. Daylight)

Northern daylight (hence CRI) can be affected by

Time of day

Cloud cover

Humidity

Pollution


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CRI and Time of Day

Morning and evening Shorter wavelengths scatter

before penetrating atmosphere

Daylight rich in yellow/orange,

lacks blue/green

Mid-day

Hours around noon = ideal Incident daylight is most

balanced within VLS

Full spectrum of colors visible


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Color Temperature

Another light source reference standard Related to the color standard black body when

heated

Reported in degrees Kelvin (K) 1000Kred

2000Kyellow

5555Kwhite

6500Knorthern daylight 8000Kpale blue

Dependent on four factors which influence CRI


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ColorThe quality of an object or substance with

respect to light reflected by the object,usually determined visually by

measurement of hue, chroma and value


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Color

Influenced by three main factors1. Physical properties of the object

2. Assessment of the observer

3. Nature of incident light

Relationship to other colored objects


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Subtractive Color

These are the colors associated with the subtraction oflight

Used in pigments for making paints, inks, fabrics etc.

The primary subtractive colors are Red, Yellow, and Blue

The secondary subtractive colors

are Green, Purple and Orange

When subtractive primary colors

are combined they produce black


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Additive Color

These are the color obtained by emitted light

Associated with television and computer displays

The primary additive colors areRed, Blue and Green

The secondary colors are

Cyan, Yellow and Magenta

When additive primary

colors are combined they

produce white


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Complimentary Colors


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Three Attributes of Color

1. Hue

2. Chroma

3. Value


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Hue

Variety of color (red, green, yellow, etc.)

Determined by wavelength of observedlight within the VLS

Reflected wavelength determines hue


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The intensity or saturation of a hue

Low Chroma High Chroma

Chroma


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Value

The relative darkness or lightness of a color, orbrightness of an object

Range = 0-10 (0=black, 10 = white)

Amount of light energy an object reflects or

transmits

Objects of different hues / chroma can be identical

value

Restorations too high in value are easily detected

Low Value High Value


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Objects of different

chroma / hue can be identicalvalue

Value


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- Equal in Chroma / Variation in Value

- Variation in Chroma / Equal in Value

Chroma

Value


chroma can be identical value


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chroma / hue can be identical value


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Perception of Color


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Color Perception

Rods Scotopic (gray scale) vision, interpret brightness

Interpret brightness, not color

Highest concentration on

peripheral retina

Cones Photopic (color) vision

Interpret color

More active under high light

Highest concentration on central retina (macula),most color perceptive area of eye


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Color Adaptation

Color vision decreases rapidly as object is

observed

Color viewed dulls, while its compliment

increases in intensity

Fatigue

Viewing a pale blue or gray surface

between shade matching will restore color

vision


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Metamerism

Two colors that appear to be a match under agiven lighting condition but have different

spectral reflectance = metamers, the

phenomenon is metamerism.

Light Source #1Single Light Source

Light Source #2 Light Source #3


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Metamerism


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Color Blindness

Defect in color vision 8% males 0.5% females

Several variations exist

Achromat ismcomplete lack of hue sensitivity Dichromat ismsensitivity to two primary hues

Anomalous Tr ichromat ismsensitivity to all threehues, with abnormality in retinal cones affecting oneof primary pigments

Dentists shou ld have their color v is ion evaluated.

If any defic iency is detected, a dentist shou ld seek

assistance when select ing too th shades.


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Shade Selection

Subjective evaluation with considerable

variation

Subtle variations can exist without causing

disharmony in smile

Restoration contour

Value of restoration

Process improved by applying principles of

light and color


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Principles of Shade Selection

1. Teeth to be matched must be clean2. Remove bright colors from field of view

- makeup / tinted eye glasses

- bright gloves

- neutral operatory walls

3. View patient at eye level

4. Evaluate shade under multiple light sources

5. Make shade comparisons at beginning ofappointment

6. Shade comparisons should be made quickly to

avoid eye fatigue


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Commercial Shade Guides

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


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Commercial Shade Guides

Vita Classic

Vitapan 3DMaster

Extended Range Shade Guides


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Vita Classic Shade Guide

A B C D

Very popular shade guide

Tabs of similar hue are clustered into letter

groups

A (red-yellow) B (yellow)

C (grey)

D (red-yellow-gray)

Chroma is designated

with numerical values

A3 = hue of red-yellow, chroma of 3

Grey


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Red/Yellow Yellow GreyGrey

Red/Yellow


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Vita Classic Shade Guide

Manufacturer recommended sequence forshade matching

1. Hue Selection

2. Chroma Selection

3. Value Selection

4. Final Check / Revision


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Vita ClassicStep 1

(Hue Selection)

Four categories representing hue A, yellow-red

B, yellow

C, gray D, red-yellow-gray

Operator should select hue closest to that ofnatural tooth

Use area of tooth highest in chroma for hueselection Difficult to select hue for teeth low in chroma


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Vita ClassicStep 2

(Chroma Selection)

Hue selection has been made (B)

Chroma is selected from gradations within

the B tabs B1, B2, B3, B4

Several comparisons should be made

Avoid retinal fatigue

Rest eyes between comparisons (blue-gray)


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Vita ClassicStep 3

(Value Selection)

Use of second, value ordered shade guide isrecommended

Value oriented shade guide B1, A1, B2, D2, A2, C1, C2, D4, A3,

D3, B3, A3.5, B4, C3, A4, C4,

Value best determined by squinting with

comparisons made at arms length Decreases light

Diminishes cone sensitivity, increases rod sensitivity

Tooth fading first has a lower value

C S


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Vita ClassicStep 4

(Final Check / Revision)

Potential Problem

Following value selection, tabs selected for

hue and chroma may not coincide with shade

tab selected for value

Vi Cl i S 4


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Vita ClassicStep 4

(Final Check / Revision)

Possible Findings / Solutions

Value of shade tab < natural teeth

Select new shade tab with higher value

Cannot increase value of restoration with extrinsicstaining

Will only increase opacity, light transmisison

Value of shade tab > natural teeth

Select new shade tab with lower value

(or)

Bridge difference with intrinsic or extrinsic staining

VITAPAN 3D MASTER Sh d


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VITAPAN 3D-MASTER Shade

Guide


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Vita-3DStep 1

Determine the lightnesslevel (value)

Hold shade guide to

patients mouth at armslength

Start with darkest group

moving right to left

Select Value group

1, 2, 3, 4, or 5


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Vita-3DStep 2

Select the chroma

From your selected Valuegroup, remove the middle

tab (M) and spread thesamples out like a fan

Select one of the three

shade samples todetermine chroma


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Vita-3DStep 3

Determine the hue

Check whether the

natural tooth is more

yellowish or more

reddish than the

shade sampleselected


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Vita-3DStep 4

For more precise shade, intermediate

levels for hue, value, and chroma can be

given

2.5M2 = value between 2M2 and 3m2

3M1.5 = chroma between 3M1 and 3M2

3M2 / 3L2.5 = hue between 3M2 and 3L2.5


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Vita-3DValue Modification


levels for value, chroma, and hue can be

given

2.5M2 = valuebetween 2M2and 3M2


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Vita-3DChroma Modification


levels for value, chroma and hue can be

given

3M1.5= chromabetween 3M1and 3M2


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Vita-3DHue Modification


levels for value, chroma and hue can be

given

3M2 / 3L2.5= huebetween 3M2and 3L2.5

2.5

Intermediate values should be noted on the

laboratory communication form


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Extended Range Shade Guides

Most shade guides do not cover all thecolors in the natural dentition

Some porcelain systems extend the typical

range Bleached shades

Dentin shades

Custom shade guides


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Shade Mapping

Recommended even when good custom shadematch exists

Tooth is divided into Three regions

Nine segments

Each region is matched independently

Further characterizations are sketched

on diagram, may include Craze lines

Hypocalcifications

Proximal discolorations

Translucency


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Summary An understanding of the science of color and color perception is

crucial to the success in the ever expanding field of estheticrestorative dentistry.

Although limitations in materials and techniques may make a perfect

color match impossible, a harmonious color match impossible, a

harmonious restoration can almost be achieved.

Shade selection should be approached in a methodical and

organized manner.

This will enable the practitioner to make the best choice and

communicate it accurately to the laboratory.


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Thank You

the science of color, light and shade - student copy

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