This is for the color perception

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COLOR SCIENCE
M . A . Vinoth
III yr - PG

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INTRODUCTION

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Light is a visible electromagnetic energy
Measured – nanometers (nm)
Eye sensitive – visible portion of spectrum [ 380 – 780nm]
Different wavelength – different colors
Reflected light wavelength determines the particular color of an
object
LIGHT

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QUALITY OF LIGHT
3 Types
 Incandescent Light
 Fluorescent Light
 Natural Daylight
Most dental offices are outfitted with incandescent and
fluorescent lights

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INCANDESCENT LIGHT
 Incandescent Light Emits high concentration of yellow
waves
 Not suitable for shade matching

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FLUORESCENT LIGHT
 Fluorescent Light Emits high concentration of blue
waves
 Not suitable for shade matching

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 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
NATURAL DAYLIGHT

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COLOR
The quality of an object or substance with respect to light
reflected by the object , usually determined by measurement
of hue,value,chroma.

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FACTORS
Color Influenced
by three main factors
 Physical properties of the object
 Assessment of the observer
 Nature of incident light

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DESCRIPTION OF
COLOR
• Three color attributes:
(1) Hue: Particular variety of a color
(2) Chroma: Saturation or intensity of a hue
(3) Value: Relative lightness and darkness of a
color or brightness of an object

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DIMENSIONS OF COLOR
• Two systems explained,
1. Munsell order system.
2. CIE color system.

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MUNSELL COLOUR SYSTEM
 Is the system of choice in
color matching.
 It - sphere or cylinder.
 A colorless or achromatic
axis extends through the
centre of the cylinder,
 Pure white at top,
 Pure black at bottom.

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 Colours are purest on the outer
skin of the cylinder,
 They become progressively
grayer as they approach the gray
value axis.
 The cylinder may be considered
as a series of wheels stacked one
upon the other.
 Each wheel of ascending
lightness as we progress to the
top.
MUNSELL COLOUR SYSTEM

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 The hub of each wheel
represent the Value axis.
 The Hues are arranged
sequentially around the rim.
 Each Hue is divided into10
segments equally spaced
around the perimeter of the
cylinder.
MUNSELL COLOUR SYSTEM

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MUNSELL COLOUR SYSTEM
Three dimensional system
Hue
Chroma (saturation or intensity)
Value (luminosity or brightness)

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HUE
Describes dominant color of an object.
Eg :- red, green or blue.
Shorter wavelength- violet spectrum.
 larger wavelength - red portion.

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In Munsell’s words, “it is that quality by which we
distinguish one color family from another.”
Generally there are 6 Hue families;
1. Violet,
2. Blue,
3. Green,
4. Yellow,
5. Orange,
6. Red.
HUE

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CHROMA
Represents to degree of saturation of a particular hue.
 Chroma varies horizontally.
Human teeth fall into the yellow to yellow red area.

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A simple way to visualize chroma is the bucket of
water.
One drop of ink is added, a solution of low chroma
results,
Adding a second drop increases chroma.
Intensity of chroma of a particular hue is more
intense on the outer rim than near hub of the wheel.
CHROMA

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VALUE
Lightness or darkness of the color.
Value increases towards the top (whiter) & decreases toward
the bottom (darker or more black).
Eg: the yellow of a lemon is lighter than a red of a cherry).

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 The degree to which light is transmitted rather than
absorbed or reflected
Highest translucency – transparent
 Lowest -opacity
TRANSLUCENCY

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CIE COLOR SYSTEM
 Commission Internationale
on illumination.
 Introduced in 1976.
 The values used by CIE
are called L*, a* and b*.
 Three coordinates define
lightness,
red green chromacity,
yellow blue chromacity.

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 L* represents the difference between light(where L*=100), &
dark(where L*=0).
 a* represents the difference between green (-a*) & red(+a*).
 b* represent the difference between blue ( -b*) & yellow ( +b*) .
CIE COLOR SYSTEM

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 Retina (rods+cones) Optical Centre in the brain
 Scotopic Vision: under low lightning conditions. Rods used.
 Photopic Vision: under higher lighting. Cones used.
COLOR PERCEPTION

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Color vision decreases rapidly as object is observed Leads
to retinal Fatigue
 Viewing a pale blue or gray surface between shade
matching will restore color vision
COLOR ADAPTATION

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COLOR BLINDNESS
Defects in color vision
8% - male
0.5% - female
Achromatism
Dichromatism
Trichromatism

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REVIEW OF LITERATURE
Barna et al, 1981, reported that color vision deficient
dentists serving as subjects have lower color discrimination
abilities than those of normal dentists and suggested that
color vision-deficient dentists should obtain assistance when
matching tooth shades.
Davison et al (1990) found that dental personnel with
color vision deficiency made significantly greater errors in
hue and chroma selection than normal- vision dental
personnel.

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METAMERISM
The change in color perception of two
objects under different light sources.
Eg:- yellow object normally reflects
yellow light, but some may actually
absorb yellow light & reflect orange &
green.
This means sample that appears to
match under the operatory light may no
longer be satisfactory in day light.
Can be avoided by confirming it under
different lighting source.

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SHADE SELECTION
Mainly Includes Three Things
Object
Observer
Light

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1. Manual
— Shade guides
Vita Classic (Vita, Bad Sackingen, Germany)
Vitapan 3D-Master (Vita)
Chromascop (Ivoclar-Vivadent, Schaan, Liechtenstein)
Custom or specific chroma and value Guides
2. Instrumental
– Spectrophotometers
– Colorimeters
– Digital cameras
METHOD OF SHADE
SELECTION

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PRINCIPLES OF SHADE
SELECTION
1. 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

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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 3D –Master
Extended Range Shade Guides

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Vita Classic Shade Guide
A B C D
Very popular shade guide
Clark – mid 1950 – 16 tabs – 4 groups
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

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Vita Classic Shade
Guide
Manufacturer recommended sequence for
shade matching
1. Hue Selection
2. Chroma Selection
3. Value Selection
4. Final Check / Revision

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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

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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)

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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

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Vita Classic – Step 4
Potential Problem
– Following value selection, tabs selected for hue
and chroma may not coincide with shade tab
selected for value
(Final Check / Revision)

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VITAPAN 3D-MASTER Shade
Guide
During - 1990

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Vita-3D – Step 1
Determine the lightness
level (value)
Hold shade guide to
patient’s mouth
Start with darkest group moving
right to left
Select Value group
1, 2, 3, 4, or 5

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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

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Vita-3D – Step 3
Determine the hue
Check whether the natural
tooth is more yellowish or
more reddish than the
shade sample selected

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Vita-3D – Step 4
For more precise shade, intermediate levels for hue,
value, and chroma can be given

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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

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Gabriele et al. 2009
The aim of this study was to test the ability of a ceramic
system to correctly reproduce the selected shade with
reference to two available shade guides.
 It was concluded that the shade matching ability of the
VITA 3D-Master Tooth Guide was found to be more
reliable than that of the VITA Classical Shade Guide.
REVIEW OF LITERATURE

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CHROMASCOP – Shade
Guide
Twenty chromatically arranged shades make shade
selection
- Additionally bleach shades are included

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Dentin Shade Guide
Can be used to communicate color of the prepared
tooth to the technician when translucent ceramic
system is used

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LIMITATIONS OF SHADE GUIDES
Limitations of shade guides are failure to account
for the variability found in natural teeth:
 Degree of fluorescence
 Degree of opalescence
 Degree of enamel translucency
 Enamel thickness
 Enamel texture
 Objectivity
 Don’t tell about the complete tooth color.
 Shade guide is prepared by different materials and crowns are of
different.

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SHADE MAPING
 Is used to communicate the accurate shade
distribution to the technician
 A tooth is divided to 3 regions: cervical,
middle, and incisal
 Each region is matched independently
 Individual characterizations like discoloration,
hypo calcification, Craze lines and
translucent are transferred to the chart as well

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Paul et al in 2002
computer color analysis
more accurate
than human shade selsction

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• Can be made using:
 Spectrophotometers,
 Colorimeter.
 Digital camera .
Color-Measuring Instruments

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SPECTROPHOTOMETERS

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Most accurate
Measure the amount of light energy reflected from an object
at 25nm intervals along the visible spectrum.
It contains
Source of optical radiation – dispersing light
Optical system – measuring
measurements are performed with an optic handpiece
Detector – converting light to signal – analyzed
The data obtained – manipulated & translated to shades
which matches dental shade guides
SPECTROPHOTOMETERS

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Paul et al 2004.
The goal of this study was to find the shade match of single
porcelain-fused-to-metal restorations with the adjacent dentition when
the restorations were fabricated according to data from conventional
visual shade matching or spectrophotometric system.
It was finalized that spectrophotometric crowns were preferred over
conventional crowns.
REVIEW OF LITERATURE

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Tung et al.
have stated that the widespread use of spectrophotometers
in dental research and clinical settings has been hindered by the fact
that the equipment is complex and expensive and, more importantly,
that it is difficult to measure the colour of teeth in vivo with these
machines.
REVIEW OF LITERATURE

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Directly measures color as perceived by human eye
Filter the light in 3 or 4 areas of the visible spectrum
to determine the color of the object
Advantages :-
simple
reliable
significantly accurate
Disadvantages :-
flat surface
significant edge loss effects
systematic errors
COLORIMETERS

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DIGITAL CAMERAS

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Most basic approach to electronic shade taking
Require certain degree of subjective shade selection
with human eye
To transfer this data
clear match software system is used
industry shade guides
by comparing this data
shade is selected
DIGITAL CAMERAS

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John D et. al. 2008
The main objective of study was to determine the clinical
effectiveness of a spectrophotometric shade-matching system
on tooth color reproduction.
Within clinical limitations of the study it was concluded
that, spectrophotometric color-matching method was
significantly higher than the crowns fabricated using a
conventional method.
REVIEW OF LITERATURE

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CONCLUSION
An understanding of science of color & its
perception is crucial for the success in the ever
expanding field of esthetic dentistry.
Limitations in materials & techniques may make a
perfect color match impossible.
Can be minimized by approaching in a methodical
& organized manner, then communicating it
accurately to the laboratory.

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REFERENCES
 Anusavice K J; Phillips’ science of dental materials 11thed .
 Rosenstiel S F; Contemporary fixed prosthodontics 4thed .
 Shillinburg H T; Fundamentals of fixed prosthodontics 3rded .
Clinical performance of a newly developed spectrophotometric system on tooth color
reproduction
John D. Da Silva et. al. J Prosthet Dent 2008;99:361-368
Conventional visual vs spectrophotometric shade taking for porcelain fused- to-metal crowns: a
clinical comparison Paul SJ, Peter A, Rodoni L, Pietrobon N. Int J Periodontics Restorative Dent
2004;24:222-31.
Four color-measuring devices compared with a spectrophotometric reference system
Karl Martin Lehmann et. al., J Dent. 2010;38 Suppl 2:e65-70.

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