The modern dentist must be trained to detect differences in color and shades in individual teeth, select a shade that reflects the color and exact shade, transmit this information to a dental technician, and be able to deliver an esthetic restoration.
3. CONTENTS
Introduction
Elements of Color
Physics of light
Science of color
Perception of color
Color in dentistry
Shade matching
Currently available shade matching devices
Conclusion
References
3
4. 4
INTRODUCTION
• Being prosthodontist, we deal with
restorative dentistry. Restorative dentistry
is a blend of science and art.
• Aesthetics which is one of the main
concerns in the restorative dentistry
depends totally upon proper shade
matching of prosthesis with surrounding
structures which can be teeth or soft
tissues.
5. • Color matching is done for better compliance.
• Perception of color is physiological response by
human eyes and sensory structures of brain towards
the light reflected from an object.
5
6. NATURE OF COLOR
• Color is all about light.
• For color to be seen , light is reflected from an object
and stimulates the neural sensors in the eye’s retina to
send a signal that is interpreted in visual cortex of brain.
6
7. LIGHT
5. Shammas A, Alla RK. Color and shade matching in dentistry. Trends Biomater. Artif. Organs 2011;25(4):172-75.
7
Light is a part of electromagnetic
waves.
9. • White light which is seen by human eye is
called visible light that falls in the range of
380 to 780 nm.
• Other waves like radio, micro, infra, x rays
and gamma rays cannot be seen by
human eyes so called the invisible
spectrum. Both visible and invisible
spectrum make up the electromagnetic
spectrum.
9
11. • Relatively equal quantities of electromagnetic
energy over the VL
Pure White Light
770nm
380nm
+ + + + + + =
11
by sir Isaac newton in 1676
12. COLOR
• Color is a property of light.
• Objects have no color of their own, they just
reflect a particular wavelength from the color
spectrum.
• For e.g., blue objects absorbs all of the
wavelengths, except for blue.
12
13. Color6
1: a phenomenon of light or visual
perception that enables one to
differentiate otherwise identical objects
2: the quality of an object or substance
with respect to light reflected or
transmitted by it. (GPT9)
13
17. INTERFERENCE
17
If the crest of one wave coincide with crest of another
wave the amplitudes are additive while if crest of one
wave coincide with trough of another wave resultant
amplitude is decreased or may be even cancelled. This
is destructive interference.
19. SCATTERING
19
It is scattering of light that makes sky appear blue, make
clouds white and turns the sun red at sunset. In the air, part of
the sunlight is scattered. THE SHORTER THE
WAVELENGTH THE MORE IS SCATTERING. Therefore in
the scattered light the shorter wavelengths predominate
20. COLOR PERCEPTION
20
rods and cones are photoreceptors that process light into nerve impulses.
Rods are 120 million in no. and helps in adjusting vision in dim light or low light levels
Cones are 6 millions in no. and adjust vision in bright light and sensitive to color.
21. Lighting conditions
21
Low lighting condition
Only rods are used.
High lighting
condition
Cones are used
Scotopic
vision
Photopic
vision
Dark
adaptation
40 mins.
22. Primary requisites for perception of
color
1. The object
2. A light source for illumination
3. An observer
• The most important phenomena that come into play
during color matching are:
1. Successive contrast
2. Simultaneous contrast
3. Color constancy
22
23. Color matching
23
successive
contrast simultaneous
contrast
color
constancy
projection of a
negative afterimage
(complementary
color) that occurs
after staring at a
colored object.
instantaneous change
in chromatic sensitivity
characterized by a
change in appearance
of hue due to
surrounding colors.
occurs because we think
of objects themselves as
being colored, so that an
object seems to be the
same color even if the
light received by the eye
varies considerably .
24. successive contrast
24
Occurs when one color is viewed following the observation of
another color.
Positive
afterimages
Negative
afterimages
25. Simultaneous contrast
25
Perception of color is affected by three
factors :
Surrounding relative lightness:
Surrounding color:
Surrounding relative saturation:
26. Color constancy occurs because we think of objects
themselves as being colored, so that an object
seems to be the same color even if the light
received by the eye varies considerably .
26
Color constancy
27. Color adaptation13
Color vision decreases rapidly as object is
observed.
Original color appears to become less & less
saturated until it appears almost grey.
Simultaneously, Chroma of complementary colors
appears greater.
27
29. Quality of Light
LIGHT
INTENSITY
PROPER
ILLUMINANTS
COLOR
TEMPERATURE
COLOR
RENDERING
INDEX
29
Proper illumination is necessary for accurate perception of color.
not only enough lightening is required to evaluate color properly but it is also essential to
achieve a proper quality of light.
This is accomplished by using the correct light intensity and the proper illuminants.
The appropriate color temperature and color rendering index must be considered when
selecting a light source.
32. Color Rendering Index
• Indicates how well a light source renders color as
compared to a standard source.
0 100
32
33. Natural Daylight
Daylight is often used as the standard against which
other light sources are compared.
CRI is 100
Distribution of light wave from the sun depends upon:
time of day
on humidity
on pollution
33
34. During morning & evening hours the
shorter wavelength light (blue &
green) are scattered, & only longer one
(at the red end of spectrum) penetrate
the atmosphere.
Northern daylight around noon hour
on a bright day considered ideal
because there is harmonious balance
within the visible light spectrum.
34
35. Northern day light has an average color temperature of
around 6500⁰ K, but this varies with the time of day,
humidity & pollution.
35
36. STANDARD ILLUMINANTS
International Commission on Illumination ( CIE),
In 1931
A B C
Tungsten light source
with color temperature
of about 2,856K
yellowish red light
Tungsten light
source coupled
with a liquid filter
direct sunlight
(noon) with color
temperature of about
4,874K
average daylight (shady/
indirect sunlight) with
color temperature of
6,774 K.
36
37. STANDARD ILLUMINANTS
International Commission on Illumination,
D E F
different daylight
conditions as measured
by color temperature.
Theoretical light
source with equal
amounts of energy at
each wave length.
Series of fluorescent
light sources
D50 D65 37
38. STANDARD ILLUMINANTS
F
L
There is a coating on the
spirals, which makes this
light white.
CRI = 50-80.
CRI = 80-98
COMPACT FLUORESCENT
LIGHT (CFL’S)
LIGHT EMITTING
DIODES
38
39. • Light source with color temperature close to 5500 k i.e. D55
which is spectrally balanced throughout the visible spectrum
is ideal for color matching.
• D65 is considered to be true color temperature of white light
as perceived by human observers.
• Is commonly used standard lighting for visual shade
matching in dental clinic.
39
42. • Enamel and dentin have different structural
characteristics and consequently they exhibit
different light wave interaction
• Enamel due to its highly mineralized prismatic
structure, low organic content and a small amount of
water have a higher transmission of light than
dentin.
• Dentin has less mineral content, an organic tubular
structure and higher water content and is less
translucent.
42
43. 43
At the incisal third the enamel is 1.5mm and lends to translucency
In middle third it becomes more translucent
And in cervical third it thins out to 0.2-0.3mm making it transparent and
showing underlying dentine
44. OPALESCENCE44
Scattering of smaller wavelengths of the visible spectrum and
transmission of longer wavelengths
making the opalescent objects more bluish when viewed
under reflected light and more orange when viewed in
transmitted light
45. • Human teeth enamel is opalescent.
• At the incisal edges of the teeth the longer
wavelengths are transmitted while the shorter
wavelengths are reflected via scattering.
• Thus enamel appears bluish dispite being colorless.
45
46. • All teeth that are naturally covered by the enamel
present opalescence
• However, better observed in the upper central incisors,
in the form of a blue band, located near to the incisal
edge called opalescent halo.
46
47. FLUORESCENCE
luminescence phenomenon, which means that it causes
spontaneous light emission by a process other than heating
47
Natural teeth as observed in
Daylight and black light
48. • Fluorescence is present in both enamel and dentin;
• it is associated with the amount of organic matter, it
presents three times greater intensity in dentin
than in enamel This difference results from the
presence of collagen fibers
48
49. METAMERISM13,10
Two colors that appear to be a match under a
given lighting condition but have different spectral
reflectance are called metamers, & phenomenon is
called metamerism.
49
Sproull R C. Color matching in dentistry. Part III. Color control. J Prosthet Dent1974;31(2):146-154.
50. This means that a sample that appears to match
under the operatory light, may no longer be
satisfactory in daylight.
Problem of metamerism can be avoided by selecting
a shade & confirming it under diff lighting conditions.
E.g; natural daylight
fluorescent light.
50
52. BASIC COLOR SCHEMES
• The color wheel is basic tool for combining colors.
• Primary colors – Red
Yellow
Blue
• Secondary colors – Green
Orange
Purple
• Tertiary colors
52
53. COLOR HARMONIES
• Two or more colors having fixed relation in a color wheel.
1. Complementary color scheme
2. Analogous color scheme
3. Triadic color scheme
4. Tetradic or rectangular color scheme
5. Split complementary color scheme
6. Square color scheme
53
56. DIMENSIONS OF COLOR
At the beginning of 20th century, Professor ALBERT
H. MUNSELL noted that each color has a logical
relationship to all other colors.
He brought clarity to color communication by
establishing an orderly system for accurately
identifying every color.
56
57. MUNSELL COLOR ORDER
SYSTEM1,2,4,10,13
Most popular method for describing color .
• Albert Munsell was an artist and teacher who developed The Atlas
of the Munsell Color System in 1915.
This color wheel includes the dimensions of :
HUE
VALUE
CHROMA
57
58. HUE
• often referred to as the basic color of an object.
• Refers to the dominant wavelength present in
spectral distribution.
• The attribute of color by means of which a color is
perceived to be red, yellow, green, blue, purple, etc.
• White, black, and grays possess no hue.
58
59. Hue of an object determined by the wavelength.
Shorter the wavelength , closer the hue will be to
the violet portion of spectrum; the longer the
wavelength , closer it will be to the red portion.
59
60. In Munsell color system, Hues are divided into 10
gradations:
Yellow
Yellow-red
Red
Red-purple
Purple
Purple-blue
Blue
Blue-green
Green
Green-yellow
60
62. CHROMA
1. the purity of a color, or its departure from white or gray
2. the intensity of a distinctive hue; saturation of a hue
3. chrome describes the strength or saturation of the hue
(color)
Achromatic shades have a Chroma near 0.
Natural teeth are found with Chroma ranges from 0.5 to 4.
62
63. VALUE
Defined as relative lightness or darkness
of a color or brightness of an object.
Brightness of an object is direct
consequences of the amount of light
energy the object reflects or transmits.
Value is the only dimension of color that
may exist alone.
63
64. In Munsell system, Value is divided into 10
gradations, with 0 being Black & 10 being White
Natural teeth range in Value from 5.5 to 8.5
A restoration that has too high a Value may be
easily detected & is common esthetic fault in
metal- ceramic prosthesis.
64
65. RELATIONSHIP BETWEEN DIMENSIONS
OF COLOR
Munsell color solid can be represented
in following manner:
Hues are uniformly spaced around
central axis of color wheel.
Centre of wheel is achromatic or Value
portion.
Each spoke of the wheel represents
the gradations in Chroma occuring
within a hue.
65
66. The wheels on the top of the stack have higher Value
than those on the bottom of the stack.
Wheels are not the same size because it is not
possible to achieve the same degree of color purity,
or Chroma, for all Hues.
66
67. CIELAB COLOR SYSTEM1,2,4,10,13
Determined by Commission Internationale de I’Elcairagein
1978.
CIELAB relates the tristimulus values to a color space.
In this system the color differences which you perceive
correspond to distances measured colorimetrically
67
69. 69
• Cielab color order defines color space by three
coordinates L, a and b.
• where L is similar to value in munsell color system.
• a and b represents chromatic characteristics of a color.
• a represents red green axis and b represents yelllow blue
axis.
• L refers to lightness coordinate ranging from 0 to 100.
• +ve a values reflect red color range , negative a green
color range
• +ve b indicate yellow color range.
73. COLOR BLINDNESS
Is caused by a deficiency in or absence of one or
more photosensitive pigments present in cones.
Defects in color vision affects about 8 % of the male
population & less of the female population.
Diff types exist:
Achromatism– complete lack of Hue sensitivity.
Dichromatism-- sensitivity to only 2 primary Hues
either red or green are not perceived.
73
74. Anomalous trichromatism– sensitivity to all three
Hues with deficiency or abnormality of one of the
three primary pigments in the retinal cones.
Dentists should have therefore there color
perception tested.
If any deficiency detected, dentist should seek
assistance when selecting tooth shades.
74
75. There are a number of chronic diseases that can have
significant affects on color perception as well.
Diabetes, glaucoma, leukemia, Addison disease,
pernicious anemia, sickle cell anemia, multiple
sclerosis, Parkinson disease, liver disease, and
alcoholism have been shown to compromise color
vision .
75
76. AGE
• Aging is detrimental to color-matching abilities because
the cornea and lens of the eye become yellowish with
age, imparting a yellow-brown bias.
• This process begins at age 30, becomes more
noticeable at age 50 and has clinical significance after
60 years of age.
• After age 60, many people have significant difficulties
in perceiving blues and purples.
76
77. FATIGUE
• Tired eyes cannot perceive color as accurately as alert
eyes.
• Compromised visual perception is due to systemic,
local or mental fatigue.
• Successive shade observations (treating many
patients requiring shade assessment during a single
workday) can be primary cause of fatigue.
77
78. BINOCULAR DIFFERENCE
• The perception difference between the left and the
right eye.
• To test for binocular difference, two objects are placed
side by side under uniform illumination. They may
appear different, e.g., the one on right may seem
slightly lighter than the one on the left.
78
79. • Placing shade tabs either above or below (rather than
next to) the tooth to be matched will help to
eliminate error caused by binocular difference.
79
80. SHADE SELECTION
Shade – a term used to describe a particular
Hue, or variation of a primary Hue, such as
greenish shade of yellow.
OR
A term used to describe a mixture with black or
gray as opposed to a tint that is a mixture with
white. (GPT-9)
80
81. GENERAL PRINCIPLES15
81
Sorensen J A, Torres T J. Improved color matching of metal-ceramic restorations. Part-1: A
systematic method for shade determination. The Journal of Prosthetic Dentistry
1987;58(2):133-9.
Neutral colored shade matching environment should be created i.e. the
walls, staff clothing and patient drape should be ideal neutral grey.
Any lipstick or bright makeup done by the patient have to be removed
Drape the patient with a neutral-colored cover if the patient is wearing
bright-colored clothing.
82. • Shade selection should be done at the beginning of
the appointment
This is because the eyes of dentist are not fatigued
from dental procedures.
Moreover, teeth become dehydrated and change
color during preparation and the debris generated in
the form of enamel, metal and cement grindings can
coat everything in the mouth.
82
83. Have the patient’s mouth at dentist’s eye level.
Rapid shade comparison should be made for
no more than 5 seconds.
83
84. GENERAL PRINCIPLES15
• Assess Value levels by squinting.
Half-closed eyes decrease the amount of light
entering the eye to inactivate the cones and
allow peripherally located rods of the retina to
discriminate lightness and darkness.
84
85. GENERAL PRINCIPLES15
• Compare shade selection under varying
conditions
wet versus dry (Teeth increase in Value when they
are dry.)
Lip retracted versus lip down, under different
lighting conditions.
85
86. GENERAL PRINCIPLES15
Canines should be used as reference in selecting a
shade because they have the highest chroma of the
dominant Hue of the teeth.
Maxillary incisors are similar in Chroma to premolars.
Mandibular incisors are usually one Chroma level lower
than maxillary incisors.
Canines are two Chroma levels higher than maxillary
incisors.
86
87. Shade comparison should be made quickly, with the
color sample placed under the lip directly next to
the tooth being matched.
This will ensure that the background of tooth &
shade sample are the same, which is essential for
accurate matching.
87
88. Shade selection should be made at 3 to 6 feet
from the oral cavity is more useful, since it is
representative of the conditions under which
patient’s teeth will most often be observed.
Verification of the shade should be made in the
presence of second individual such as dental
assistant.
88
91. VITA CLASSICAL SHADE GUIDE
91
Introduced in 1960 by Vita Zahnfabrik, Germany
16 tabs are available in 4 hue groups categorized as A,B,C and D
92. • A1-A4 Reddish-brownish
• B1-B4 Reddish-yellowish
• C1-C4 Greyish shades
• D2-D4 Reddish-grey
92
1 is least chromatic and highest value
4 is most chromatic lowest value.
93. HUE SELECTION
Choosing the nearest Hue 1st & then selecting the
appropriate match of Chroma & Value from the tabs
available is the recommended technique.
The region with the highest Chroma (cervical region
of canine), should be used for initial Hue selection.
93
94. CHROMA SELECTION
Once Hue is selected, the best Chroma match is chosen.
Several comparisons are necessary when determining
which sample best represents the Hue & its corresponding
Chroma level.
Between comparisons glancing at grey object, will rests to
operators eye & help avoid retinal cone fatigue.
94
95. VALUE SELECTION
Value is determined by arranging the samples in
increasing lightness by holding the shade guide close
to the patient.
95
96. 96
It has been rearranged according to the value based ordering system
(B1, A1, A2, D2, B2, C1, C2, D4, D3, A3, B3, A3.5, B4, C3, A4,C4)
99. • VITA Bleached Shades offer the dentist a practical
tool for the reliable determination and maintenance
of a whitening regimen
• consist of the bleached shades 0M1, 0M2 and 0M3.
99
101. • Introduced by Ivoclar Vivadent
• USES NUMBERING SYSTEM
• 100 = WHITE
• 200 = YELLOW
• 300 = ORANGE
• 400 = GRAY
• 500 = BROWN
101
Grouped into 5 series by
HUE
Chroma and value are communicated
by another system of numbers
10 = least chromatic, highest value
40 = most chromatic , lowest value
102. VITA TOOTHGUIDE 3D-MASTER
• It is a value based shade guide and value based shade
guides are a more accurate means of shade selection
103. VITA 3D MASTER SHADE GUIDE
• Introduced in 1998 by Vita Zahnfabrik
• 26 tabs arranged three dimensionally.
• 5 basic value groups from lighter to darker
• Chroma varies vertically downwards 1 to 3
• Hue varies horizontally as L, M, R.
103
104. • Step 1- Value selection with VITA 3D MASTER
• (levels 1 being lightest (high value) and 5 being darkest (low
value))
• Start with darkest group moving right to left.
104
105. 105
Step II: Chroma selection with VITA 3 D MASTER
the chroma (levels 1 2,3) is determined with 1 being least
chromatic and select the color sample of the selected M group
that is closest to the tooth to be compared.
111. DENTIN SHADE GUIDE
When using a translucent all ceramic system for a
crown or veneer, communicating the shade of the
prepared dentin to the dental lab is helpful.
111
112. CUSTOM SHADE GUIDE
An almost infinite number of samples can be made by
using different combination of porcelain powders in
varying distribution.
Procedure is time consuming.
Confined to specialty practice.
112
113. SHADE DISTRIBUTION CHART
Shade distribution charting is a practical approach to
accurate shade selection & is recommended even
when a fairly good match is available from commercial
shade sample.
Tooth ------ cervical
middle matched independently,
incisal
113
114. The junction areas can be
communicated to lab in the
form of diagram.
Individual characteristics are
marked on such a sketch &
will allow the ceramist to
mimic details like hairline
fracture, hypocalcification &
proximal discolorations.
114
115. SHADE TAKING DEVICES13,18
These devices have been designed to aid clinicians and
technicians in the specification and control of tooth color.
The earliest color-measuring device designed specifically
for clinical dental use was a filter colorimeter.
The Chromascan was introduced in the early 1980s but
enjoyed limited success due to its inadequate design and
accuracy.
115
116. BASIC DESIGN
All color-measuring devices consist of
a detector,
signal conditioner, and
software
that process the signal in a manner that makes the
data usable in the dental operatory or laboratory.
116
118. COLORIMETERS
Filter colorimeters generally use three or four
silicon photodiodes that have spectral correction
filters that closely simulate the standard observer
functions.
These filters act as analog function generators
that limit the spectral characteristics of the light
that strikes the detector surface.
118
119. The inability to exactly match the standard
observer functions with filters while retaining
adequate sensitivity for low light levels is the
that the absolute accuracy of filter colorimeters is
considered inferior to scanning devices such as
spectrophotometers and spectroradiometers.
119
120. However, because of their consistent and rapid
sensing nature, these devices can be precise with
differential measurements.
This is why they often are used for quality control.
120
121. DIGITAL CAMERAS AS FILTER
COLORIMETERS
The newest devices used for dental shade matching are
based on digital camera technology.
Instead of focusing light upon film to create a chemical
reaction, digital cameras capture images using charge
couple devices, which contain many thousands or even
millions of microscopically small light-sensitive elements
(photosites).
Like the photodiodes, each photosite responds only to the
total light intensity that strikes its surface.
121
122. SPECTROPHOTOMETERS &
SPECTRORADIOMETERS5
Spectrophotometers and spectroradiometers are
instruments designed to produce the most
accurate color measurements.
Spectrophotometers differ from
spectroradiometers primarily because they include
a stable light source.
There are two types of basic designs commonly
used for these instruments.
122
123. The traditional scanning instrument consists of a
single photodiode detector that records the amount
of light at each wavelength.
The light is divided into small wavelength intervals
by passing through a monochromator.
A more recent design uses a diode array with a
dedicated element for each wavelength.
124. This design allows for the simultaneous
integration of all wavelengths. Both designs are
considerably slower than filter colorimeters but
remain the tools that are required to examine
and develop accurate color-measuring devices.
124
125. CURRENTLY AVAILABLE
DEVICES18
The devices are generally one of three types—
colorimeters, spectrophotometers, or digital
color analyzers—and use various measuring
geometries .
125
127. SHADE EYE-NCC
127
Free standing hand held
contact probe
DOCKING UNIT
Shofu’s shade NCC (natural color concept) has been
available since 1990’s. it consists of a free standing hand
held contact probe about 3mm in diameter
128. 128
The probe is placed against the tooth, and an activation button is pushed.
This sends a flash of light to the tooth, from the periphery of the probe, and the reflected light is
transported through the center of the probe to the detector where the collected light is evenly
distributed through color filters that closely match the three standard observer functions.
133. SHADE SCAN
• Employs digital artificial vision technology with
integrated CAD/CAM technology.
• Shade is measured by hand held optical device
• Generates a shade map of the tooth, keying different
areas of the dental surfaces to the selected shade
guide by utilizing different resolution.
133
135. SPECTRO SHADE
Most complex in design and most
cumbersome in terms of
hardware.
Windows based system utilizes
dual digital cameras linked
through optic fibres to a fully
functional spectrophotometer.
It indicates the deviation of hue,
value, chroma from a standard.
135
136. • The handpiece is relatively large compared with the
contact probe designs, and positioning can be tricky
• Light from a halogen source is delivered through fiber
optic bundles and lenses to the tooth surface at 45.
138. SHADE -RITE139
It consists of a hand-held device with its own light source, and an LCD screen facilitates
positioning on the tooth
139. SHADE -RITE
• Cone shaped sensor is pointed at the tooth to be
replaced, at the junction of the gingival and middle
thirds of the tooth.
• Images are acquired and replaced in its cradle.
• As the unit enters the docking station, it initiates the
system’s software
• Data is uploaded and software selects the most
appropriate shade.
140
141. • The modern dentist must be trained to detect
differences in color and shades in individual
teeth, select a shade that reflects the color and
exact shade, transmit this information to a
dental technician, and be able to deliver an
esthetic restoration
142
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