(from chu, sj et al. fundamentals of color: shade matching ... · pdf filethe munsell color...

(from Chu, SJ et al. Fundamentals of Color: Shade Matching and Communication In Esthetic Dentistry. Quintessence 2004)

Color and Shade Selection

Edmond R. Hewlett, D.D.S.

Esthetic Dentistry RT443cUCLA School of Dentistry

Spring, 2005

Overview

SeeColor science & perceptionTooth optics

EnableThe environment

CommunicateVita Shade GuidesPhotos

E. Hewlett, DDS

What is Color?

E. Hewlett, DDS

What is Color?

Color is defined as the quality of an object or substance with respect to light reflected by it, usually determined visually by measurement of hue, chroma, and value.

E. Hewlett, DDS

The Munsell Color System

Professor A.H MunsellBasic principles first published in 1905

Munsell Color CompanyEst. 1918 to develop color standards

Continued development at Nat’l. Bureau of Standards, Optical Soc. of America

E. Hewlett, DDS


1940’s - Revised Munsell system standardized by:

International Commission on Illumination (CIE).American Society for Testing and Materials

Munsell System is an internationally-accepted standard for art, science, and industry

E. Hewlett, DDS


Color components:

Hue

Chroma

Value

E. Hewlett, DDS

Hue

The color itself

The attribute of a color by which we distinguish red from green, blue from yellow, etc

E. Hewlett, DDS

Chroma

The intensity of the color

Low chroma ≡ “weak”

High chroma ≡“highly-saturated”

E. Hewlett, DDS

Value

The brightness of the color

High value = brighter (more white)Lower value = darker (more gray)

Value of 0 = blackValue of 10 = white

E. Hewlett, DDS

Value (Brightness, aka Lightness)

Brightness is the most important color variable in dental shade selection!

E. Hewlett, DDS

Munsell Color Space

Arrangement of all colors according hue, chroma, and value in a 3-D space

E. Hewlett, DDS

Other Color Terms

Opacityimpenetrable by lightreflective – neither transparent or translucent

Transparencycapable of transmitting light

Translucencydiffused transmission of light

E. Hewlett, DDS

Color Perception

E. Hewlett, DDS

Color Perception

Similar colors appear different under different conditions due to

Light source type and angulationSize and shape differencesInfluence of background color & lightingPerception angle (perception is altered by direction and reflection)

E. Hewlett, DDS

Perception

eye

environment object surface

E. Hewlett, DDS

The Human Eye

Receptors: rods and conesRods convey shades of gray (value)Cones allow brain to perceive color hues and chroma

E. Hewlett, DDS

The Human Eye

Colorblindness affects…1-in-300 females1-in-13 males

Get tested

E. Hewlett, DDS

Illumination

Everything that we see is reflected lightFull spectrum light is needed to see colorColor missing in the light source cannot be reflected

E. Hewlett, DDSImage from Chu, et al 2004

Illumination Sources

Daylight (6500° K)Variable, depending on time of day, cloud cover, etc.

Electronic flash (5500 ° K)Standardized light source (for industrial color measurement)

5000° KCRI 98 (Color Rendering Index)

E. Hewlett, DDS

Illumination Sources

Recommended lighting for accurate shade taking in dentistry:

5500 ° KReplicates northern natural midday daylightbalances all hues in the spectral curve

Working distance: 12 to 15 inchesArm’s length

Appropriate environment

E. Hewlett, DDS

Color corrected source (5, 500 K)

Incandescent source

(2,856 K)

Fluorescent source (4,000 K)

images from Chu, et al 2004

Illumination

Use the appropriate illumination source!

E. Hewlett, DDS

incandescent

5,500 K

fluorescent


Metamerism

Objects that appear similar under one condition but different under another.i.e., an object appears to be different colors when viewed under different light sources

E. Hewlett, DDS

Color corrected source (5, 500 K)

Incandescent source

(2,856 K)

Fluorescent source (4,000 K)



Metameric Pair

E. Hewlett, DDS

5,500 K Fluorescent Incandescent

Tooth #8 – unrestoredTooth #9 – crown

Metamerism

Easy to recognize, impossible to controlNewer materials help

chameleon effect; fluorescenceMay need to explain to patientFor dental ceramics:

More opaque porcelain ⇒ more metamerism!

E. Hewlett, DDS

Key Optical Properties of Teeth

FluorescenceOpalescenceTranslucency

images from Chu, et al 2004E. Hewlett, DDS

Fluorescence

Emission of visible light upon exposure to fluorescent lightDentin >> Enamel


Fluorescence

Emission of visible light upon exposure to fluorescent lightDentin >> EnamelOpaceous dentin porcelains

Dentin-like fluorescenceReduced metameric effect


Opalescence

Ability of a translucent material to…appear blue in reflected lightappear red-orange in reflected light


Opalescence

Under direct illumination…reflectance of short wavelengths (blue)Absorption of long wavelengths (red-orange)


Opalescence

Under transillumination…reflectance of long wavelengths (red-orange)absorption of short wavelengths (blue)


Opalescence

Enamel >> Dentinmore translucent, more crystalline

Incisal porcelainsCan mimic enamel opalescence


Translucency

Transmission and diffusion of lightConveys depth

and vitality

image from Chu, et al 2004E. Hewlett, DDS

Translucency

Avoid excessive translucencylowers valuerestoration is too

grey/dark

image from Chu, et al 2004E. Hewlett, DDS

Translucency

Avoid inadequate translucency (excessive opacity)

too much reflectancelifeless appearance

Axial reduction!

E. Hewlett, DDS

Control the Environment

Must surround teeth with color that aids color perceptionUse neutral colors in operatoryClose blinds

window light = daylight = contamination Cover brightly-colored clothingNo lipstick!

E. Hewlett, DDS

Always use a bibColor space of natural teeth = OrangeCompliment to orange is blue

∴ Use blue patient bibs

E. Hewlett, DDS

Control the Environment

Shade Determination

Shade Communication

Vita Shade Guide (Vitapan Classical)

Introduced in 1956

A = OrangeB = Yellow orangeC = Grey orangeD = Brown orange

E. Hewlett, DDS

Vita Shade Guide (Vitapan Classical)

Limitations:not uniformly positioned throughout tooth color spaceno standard incre-mental difference between adjacent shadesin-between shades (e.g. “A2.5”) are inaccurate

E. Hewlett, DDS

Shade Selection w/ Vitapan Classical

1. Select hue first70% will be A20% will be D10% will be B or C

(Choosing lots of B and C?)

(Check light source)(Check for colorblindness)

2. Select chroma for the chosen hue group

3. Verify value

E. Hewlett, DDS

Vita 3D-Master Shade Guide

Introduced in 1998Reflects distribution of tooth shades in natureSystematic and equi-distant coverage of the natural tooth shade spectrum

E. Hewlett, DDS


Design:

5 value levels (1-5) arranged left to right

E. Hewlett, DDS


Design:

3* chroma levels (1-3) in each value group, arranged top to bottom

*(only 2 chroma levels for value group #1)

E. Hewlett, DDS


Design:

(up to) 3 hue levels (L,M,R) for each chroma level, arranged left to right

E. Hewlett, DDS


Procedure1. Select value (lightness)

E. Hewlett, DDS


Procedure2. Select chroma from

within the selected value groupUse “M” tabs from the selected value groupChoosing between diluted & saturated

E. Hewlett, DDS


Procedure3. Select hue from

within the selected value groupIs the natural tooth more reddish (R) or more yellowish (L) than the M group?

E. Hewlett, DDS


Bleached shades now available

0M1, 0M2, 0M3Bleached shades occupy the “leftmost”(brightest) value group (group #0) on the 3D-Master guide.

E. Hewlett, DDS

Shade Selection Keys

Use correct environment and lightingSelect shade at beginning of app’t.Patient sitting uprightViewing distance ~15 in. from teethPatient’s teeth/dentist’s eyes at same level

E. Hewlett, DDS


Photograph shade tabs which match specific segments of teethPhotograph textureNote special characteristics

E. Hewlett, DDS


Look for variance between gingival, middle, and incisal thirds of teeth.

E. Hewlett, DDS

higher chroma & opacity

less chroma, higher value

high translucency, lower value

image from Chu, et al 2004

Photographs for Lab Communication

E. Hewlett, DDS

Texture Photograph

Close-up of anteriors with lens ⊥ to labial surface

Emphasizes surface texture and luster

E. Hewlett, DDS

Color Photograph

Close-up of anteriors with lens angled 15-20º to labial surface

Reflections bounce away from camera, revealing color and characterization

E. Hewlett, DDS

Photographs with Shade Tabs

Angle camera to avoid reflections from tab and teethShow at least 6-8 teethTab at same angle as teethTab as close to teeth as possible

E. Hewlett, DDS

Photographs with Shade Tabs

Tab and handle clearly visible, no reflections

Shoot as many photos as necessarydifferent tabs for different areas of teeth

E. Hewlett, DDS

Photos for All-Ceramic Restorations

Shade tab w/ teeth before preparationShade tab w/ prepared tooth/teethDesired shade(s) next to preparation(s)

E. Hewlett, DDS

Other Lab Communication Photos

Photos of provisionalsViews 5, 6, 7, & 8 as indicated

Shade photo of provisionalsIf restoration doesn’t match, photograph it in mouth with tabs

E. Hewlett, DDS

Digital Shade-Taking Devices

E. Hewlett, DDSimages from Chu, et al 2004


What are they?RGB devices, spectrophotometers, or colorimeters designed or modified for dental use



What can they do?Provide detailed data on shades in different zones of a tooth’s surface



LimitationsNot reliable for complex characteristics

sub-surface colorTranslucencyTexture effects

E. Hewlett, DDSimage from Chu, et al 2004


Bottom LineNOT a replacement for traditional methodsBest used as an ADJUNCT to traditional methods and photography

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(from chu, sj et al. fundamentals of color: shade matching ... · pdf filethe munsell color...

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