The Science of Color, Light and Shade Selection

Presented by

Lisa Fedor James D.D.S.

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

Visible electromagnetic energy whose wavelength is measured in nanometers (nm)

Without Light Color Does Not ExistWithout Light Color Does Not Exist

A yellow object absorbs all lightwaves of all colors, but reflects yellow

ColorInfluenced by three main factors

1. Physical properties of the object

2. Assessment of the observer

3. Nature of incident light

– Relationship to other colored objects

Light•Part of the electromagnetic spectrum

•The eye is only sensitive to the visible portion

of the spectrum (380 – 750nm)

•Different wavelengths constitute the different

colors we perceive

• Relatively equal quantities of electromagnetic energy 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

+ + + + + + =

Quality of Light / 3 Types

1. Incandescent Light

2. Fluorescent Light

3. Natural Daylight

Most dental offices are outfitted with incandescent

and fluorescent lights

1. Incandescent Light

• Emits high concentration of yellow waves

• Not suitable for shade matching

• Low Color Rendering Index (CRI)

2. Fluorescent Light

• Emits high concentration of blue waves

• Not suitable for shade matching

• CRI =(50-80)

3. Natural Daylight• Northern daylight considered the best

• Closest to emitting the full spectrum of white light

• Used as the standard by which to judge other light sources

• CRI close to 100

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

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

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

heated• Reported in degrees Kelvin (°K)

– 1000K – red– 2000K – yellow– 5555K – white– 6500K – northern daylight– 8000K – pale blue

• Dependent on four factors which influence CRI

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

ColorInfluenced by three main factors

1. Physical properties of the object

2. Assessment of the observer

3. Nature of incident light

– Relationship to other colored objects

Subtractive Color• These are the colors associated with the subtraction of

light

• 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

Additive Color• These are the color obtained by emitted light

• Associated with television and computer displays

• The primary additive colors are Red, Blue and Green

• The secondary colors are Cyan, Yellow and Magenta

• When additive primary

colors are combined they

produce white

Complimentary Colors

Three Attributes of Color

1. Hue

2. Chroma

3. Value

Hue

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

• Determined by wavelength of observed light within the VLS

• Reflected wavelength determines hue

The intensity or saturation of a hue

Low Chroma High Chroma

Chroma

Value• The relative darkness or lightness of a color, or

brightness 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

Objects of different

chroma / hue can be identical value

- Equal in Chroma / Variation in Value

- Variation in Chroma / Equal in Value

Ch

rom

a

Value

Objects of different chroma can be identical value

Objects of different chroma / hue can be identical value

Perception of Color

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

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

Metamerism

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

spectral reflectance = metamers, the phenomenon is metamerism.

Light Source #1Single Light Source

Light Source #2 Light Source #3

Metamerism

Color Blindness• Defect in color vision

– 8% males– 0.5% females

• Several variations exist– Achromatism – complete lack of hue sensitivity– Dichromatism – sensitivity to two primary hues– Anomalous Trichromatism – sensitivity to all three

hues, with abnormality in retinal cones affecting one of primary pigments

Dentists should have their color vision evaluated. If any deficiency is detected, a dentist should seek

assistance when selecting tooth shades.

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

Principles of Shade Selection1. Teeth to be matched must be clean

2. 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 of appointment

6. Shade comparisons should be made quickly to avoid eye fatigue

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

Commercial Shade Guides

• Vita Classic

• Vitapan 3D –Master

• Extended Range Shade Guides

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

Red/Yellow Yellow GreyGrey

Red/Yellow

Vita Classic Shade Guide

Manufacturer recommended sequence for

shade matching

1. Hue Selection

2. Chroma Selection

3. Value Selection

4. Final Check / Revision

Vita Classic – Step 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 of natural tooth

• Use area of tooth highest in chroma for hue selection– Difficult to select hue for teeth low in chroma

Vita Classic – Step 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)

Vita Classic – Step 3 (Value Selection)

• Use of second, value ordered shade guide is recommended

• 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

Vita Classic – Step 4 (Final Check / Revision)

• Potential Problem– Following value selection, tabs selected for

hue and chroma may not coincide with shade tab selected for value

Vita Classic – Step 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 extrinsic

staining• 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 Shade Guide

Vita-3D – Step 1• Determine the lightness level (value)

• Hold shade guide to patient’s mouth at arms length

• Start with darkest group moving right to left

• Select Value group 1, 2, 3, 4, or 5

Vita-3D – Step 2• Select the chroma

• From your selected Value group, remove the middle tab (M) and spread the samples out like a fan

• Select one of the three shade samples to determine chroma

Vita-3D – Step 3

• Determine the hue

• Check whether the natural tooth is more yellowish or more reddish than the shade sample selected

Vita-3D – Step 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

Vita-3D – Value Modification

• For more precise shade, intermediate levels for value, chroma, and hue can be given– 2.5M2 = value between 2M2 and 3M2

Vita-3D – Chroma Modification

• For more precise shade, intermediate levels for value, chroma and hue can be given– 3M1.5 = chroma between 3M1 and 3M2

Vita-3D – Hue Modification

• For more precise shade, intermediate levels for value, chroma and hue can be given– 3M2 / 3L2.5 = hue between 3M2 and 3L2.5

2.5

Intermediate values should be noted on the laboratory communication form

Extended Range Shade Guides• 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

Shade Mapping

• Recommended even when good custom shade match 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

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

crucial to the success in the ever expanding field of esthetic restorative 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.

Thank You