Dental Color shade /certified fixed orthodontic courses by Indian dental academy

DENTAL COLOUR SHADE

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

INTRODUCTION
Esthetics is the science of sensitive
perception; in a narrower sense: the science of
beauty.According to Microsoft "Encarta 97"
encyclopedia (1997) esthetics is a branch of
philosophy concerned with the essence and
perception of beauty and ugliness. A German
philosopher Baumgarten introduced the term
esthetics in 1753, but the study of the nature of
beauty had been pursued for centuries.
Albert Einstein is reported to have said, "If
you cannot explain it simply, then you do not
understand it well enough." This appears to be
the problem regarding color matching. In a
time of growing interest in cosmetic dentistry,
there is a need for adequate training and
communication for better and more life like
results.

The first signs of man’s interest in the facial beauty
were recorded more than 4000 years ago. Facial masks
of "ideal" shape and proportions used to be the
hallmark of royalty even in the ancient Egypt as far as
from 2600 to 2000 BC (Mack, 1996). Shape and
proportion, however, are not self-sufficient and they
are not the only parameters of beauty. Modern
concepts of esthetics in dentistry analyze this issue
using a much wider approach. Dento-facial esthetics
and various factors of patients’ perception and
expectations have become a very important part of the
prosthodontic treatment (Goldstein and Lancaster,
1984;; Bishop and Priestley, 1996. The results of an
examination of Albino et al. (1984) point out that
esthetics is the first demand of patients: 42% of the
patients indicated that appearance "very strongly"
influenced their decision to obtain treatment; 19% put
forward functional problems as the major reason, while
in 14% of cases the reason was pain. When asked to
list 14 characteristics of a denture ranking them by
importance, the patients ranked its lifelike appearance
as number one.

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Lombardi (1973) described principles of visual
perception and their clinical application to denture
esthetics. When the term "esthetic"or "unaesthetic" is
used it usually means that something is perceived as
pleasant or unpleasant. The observer’s response to a
physical stimuli is, in fact, his/her psychological and
physiological interpretation of that what he/she
perceived. The stimulus, i.e. the observed object on
one hand and the response to that stimulus on the
other are the elements of the science of visual
perception.
Tooth shape, size, position and color are classical
determinants of esthetics in prosthodontics, and color is
probably most important. A number of experts point
out the outstanding need for a systematic and
scientifically based approach to color science in dental
(especially prosthodontic) education, and its application
in clinical practice.

Prosthodontics is more concerned with
color than other dental branches, so it is
logical to expect that a dentist who has
been trained in prosthodontics should be
better in shade matching. It can also be
expected that working experience exerts
positive impact on the shade matching
quality.

According to Sproull (1974): "The
technology of color is not a simple matter
that can be learned without study neither
is it a complicated matter beyond the
comprehension
of
dentists".
Many
authors think that certain improvements
in color practice are an objective need of
dentistry (Hayashi, 1967; Sproull, 1973
b; Sorensen and Tores, 1987; Sorensen
and Tores, 1988 a; Sorensen and Tores,
1988 b).most of the authors think that
color science study should be included in
the undergraduate and postgraduate
curriculum and/or in the prosthodontics
training program.

There is a lot of perplexity and confusion
just as there are numerous insufficiently
explained questions in shade matching and
reproduction procedures. However, it is neither
easy nor simple to answer these questions. In
spite of objective and subjective inadequacies
of the shade matching and reproduction
method itself, dental material manufacturers
could be blamed for certain problems in this
area. . The problem is that the majority of
dental color standards lack a logical sample
arrangement
order
and
adequate
color
distribution; moreover, they do not match
natural teeth color range. Since natural tooth
color is not uniform, harmonization of shade
guide
samples,
dental
materials
and
prefabricated artificial teeth color composition
with the color composition of natural teeth
emerges as a yet unresolved issue.

Color disharmony was found in some
manufacturers ceramic masses intended for
certain ceramic layers (especially between
opaque and dentin ceramic powders). Also, it
cannot be positively asserted whether (and to
what extent) manufacturers manage to
standardize color in different batches of dental
materials and whether particle size differences
influence
color.
Color
reproduction
for
porcelain-fused-to-metal (PFM) restorations is
also a source of many questions, such as: to
what extent the final color of restoration is
influenced by the type of substrate, the
application method, the thickness of ceramic
layers, the number of firings and the firing
temperature.

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Color matching can be performed using visual
and/or instrumental methods. Visual color
matching methods are subjective, while
instrumental methods are objective, but still
not widespread in dental practice. Precise and
objective answers to most of the questions
mentioned could be obtained only by using
instrumental
color
matching
techniques,
because they allow numerical expression of
results. A correct interpretation of colorimetric
results requires knowledge of the basic
elements of the color science.
Def: “ Color is light,modified by an object as
percieved by an eye”.

COLOR SCIENCE
A need to overcome subjectivity, as
the major disadvantage of the visual
shade matching method, induced the
evolution of color science. Color science
is multidisciplinary and it encompasses
elements
of
physics,
chemistry,
physiology and psychology. In order to
understand the science of color, one
should be aware of some physical aspects
of light, as well as of both physiological
and psychological processes that enable
color perception.

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Webster: "Color is the sensation resulting from
stimulation of the retina of the eye by light waves of
certain lengths".
Billmeyer and Saltzman: "Color is the result of the
physical modification of light by colorants as
observed by the human eye and interpreted by the
brain".
Color is a special type of psychophysical sensation
provoked in the eye by the influence of the visible
light .That incident light, or so-called colored
stimulus, provokes the stimulation of high sensitive
eye receptors, producing the nerve impulse, which is
transported to the brain. The brain is the interpreter
that recognizes those nerve impulses as a certain
color.
To work with color, it is necessary to be acquainted
with the physical, physiological and psychological
aspects of light as well as with the basic principles of
colorimetry.

Physical, physiological and psychological
aspects of light

Psychophysics is a scientific discipline
dealing with mathematical relations between
physical stimuli and the sensations they
cause. Electromagnetic radiation that can
provoke a sensation of color is called
stimulus. Stimulus is, speaking in terms of
physics, determined by the total flux of
radiation, i.e. by the quantity of energy
transported to the retina in the function of
time
and
distributed
onto
different
wavelengths (Lemiere and Burk, 1975; Prat,
1978;
Birren,
1979;
Billmeyer
and
Saltzman, 1981).

The entire process starts with the light source,
which justifies the saying: "Color is light"
(Saleski, 1972). What one recognizes as natural
white light is daylight (not direct sunlight,
which is yellow, but sunlight reflected back
from the sky). The visible part of the spectrum
comprises electromagnetic radiation falling
between wavelengths from 380 to 780 nm. The
visible spectra range, is called monochromatic
light. White light can be separated into
monochromatic components if it passes through
prism or diffraction bars . If the wavelength of
the electromagnetic radiation is less than 380
nm, it is called ultraviolet radiation and if it
exceeds 780 nm, it is called infrared radiation

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Light source. Light source is any area or body
emitting radiation in the visible spectra range.
According to one classification, light sources can be
primary (emitting their own radiation) and secondary
(reflecting a part of the radiation from some other
light source), and according to another one, they are
divided into natural and artificial light sources. The
Sun is the most important natural light source.
The object. One seldom looks directly at the light
source. The radiation flux that reaches the eye is
almost all the time reflected from some object, which
indicates that observed object influences color
perception. The structure of the object (type of
material, texture) influences its optical properties.
The eye. Color, as well as all other visual sensations,
is brought to the brain through the eye. Visual
perception occurs owing to the optical system in the
anterior and the retina in the posterior part of the
eye .

The light reflected from the object is brought to the
observer’s eye. Light enters through the optical system
and the image is focused onto the retina. The retina is
a complex mosaic of millions of nerve endings
containing a chemical substance which transforms the
light stimulation into a nerve signal that is further
transported to the brain. There are two types of nerve
endings, rods and cones. Rods only record light, i.e.
they see in black and white. They are connected
together in bunches before reaching the brain, the
interpretive part of the system, so that they achieve
high sensitivity at the expense of fine resolution. At
high levels of illumination, they play a small part in the
vision process. Cones are nerve endings that enable
color vision. Some seven million cones are placed in the
centre of the retina, in a small pit called fovea,
subtending an angle of about 2° in the visual field.
Here, instead of the bunching found in the rod area,
there is a "one-to-one" connection with the optical
system so that their www.indiandentalacademy.com
resolving power is high.

This is the area of visual acuity, lying on the
visual axis of the eye. Cones require a higher
level of illumination to be brought into action.
This can be demonstrated by a slow increase of
illumination from complete darkness, through
dim illumination at which stage only shape can
be distinguished (rod vision), allowing only
glimpses of color, up to the stage of full
intensity of light when the function of the cones
is maximum. This experiment covers three
stages of vision: scotopic, when only rod vision
is operating; mesopic, when the cones are only
initially stimulated and rods have not been
flooded yet; photopic - full light color vision
(Chamberlin and Chamberlin, 1980).

Trichromatic character of vision . There are
many complicated theories as to how cones
function, but the simplest and most commonly
accepted is Thomas Young theory, supported by
Helmholz. It is based on the experimental fact that
a suitable mixture of three monochromatic
radiations can match any color. This trichromatic
theory postulates three different types of cones,
which are sensitive to different bands of
wavelengths. The "blue-sensitive" cones are
brought into action chiefly by light of short visible
wavelengths, the second type responding chiefly to
light of wavelengths in the middle of the visible
spectrum are called "green-sensitive", while the
third type, the "red-sensitive" cones, are most
affected by light of the longer visible wavelengths.
The visible pigments responsible for these various
functions have not as yet been positively isolated.

The distribution of rods and cones changes as
one travels outward from the fovea. The central
area (2° field), which receives the image from
an object, is rod free and color differentiation is
the best in this area. Outwards, to a 4° field,
there is a mixture of rods and cones, the
composition of which mixture can vary with
individuals. Outside of this area the cone
population falls off rapidly. The periphery of the
eye is not color discriminating, although very
sensitive to light variations, movements etc. It
is because of this varying distribution of rods
and cones between individuals that there arises
the slight difference in color discrimination
between "color normal" observers, but they are
surprisingly small among more than 90% of
people. Hence the statement: "Although all the
people have not the same sight, the majority of
them see very similar"

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The brain. Although an image may be
formed on the retina, the observer
cannot be said to "seeunless that image
is in some way conveyed to his
consciousness. A number of impulses are
set in motion by the light, and these
messages have to be conveyed to, and
interpreted
by,
the
brain
before
perception occurs.

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The electrical impulses set up in the rods and
cones are programmed and sorted out
somewhere on the way to the brain, but there
is no general agreement as to the mechanism
of sorting. There are different opinions if the
commencement is made with coding in the
retina itself, or in the tissues and nerves
immediately adjacent to it, or at intermediate
points where the nerve ganglions join to form
bundles of pathways. However, some form of
message is eventually conveyed by the optic
nerve to the appropriate part of the brain.
The messages from the rods are telling of the
light or no light, while the cone messages
convey information that gives rise to the
sensation of color.

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On reaching the brain, the messages are
decoded and refereed, as in a computer, to a
bank of stored memories, which will connect
the picture presented with something
previously experienced, and finally sensation
of something "out there in front" materializes
in consciousness. All this operation is carried
out at light speed. When one is waking, he is
presented with an avalanche of messages
from the eyes. Fortunately, the brain is
selective, ignoring what is not relevant. One
perceives only the things he is interested in or
which the brain automatically brings to his
notice of the built-in instinct for selfpreservation (Chamberlin and Chamberlin,
1980).

The most frequent complications in color perception
are chromatic adaptation, metamerism and
dichroism.
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Chromatic adaptation is defined as a color
constancy phenomenon of the perceived color of the
viewed scene. Going from daylight, into a room lit
only by incandescent lamps, one is seldom aware of
the fact that the color of everything has changed,
although reason points out that this must be so.
Metamerism which occurs when the color of two
objects looks identical when observed under one light
source but different under other light conditions
Dichroism refers to a situation when the color of an
object, viewed by transmitted light, may be different
accordingto the thickness of the sample viewed.
Blood is, for example, yellow if viewed in an
extremely thin film but is red in greater depth.

Color defining and/or measuring
Visual comparison is a comparison with
some known physical standard accepted
as referral. There are numerous systems
of visual comparison and description of
color. The easiest way is to produce some
kind of systematized and precisely
repeatable catalogue. Such catalogues
are called color atlases or color derivation
systems. The Munsell Book of Color, the
Ostwald system and DIN (Deutches
Institut für Normung) system are the
most famous color catalogs.

No matter what visual method is used, light
source and viewing geometry should be
standardized in order to obtain valid results. In
the case of instrument itself, standardization is
to be done by the manufacturer, but in case
when color atlases or some other samples are
used, adequate conditions have to be provided.
Furthermore, in all cases of visual colorimetry
before any real work starts it is necessary to
test whether the observer is color deficient. It
has already been emphasized that there are
differences among so-called "color normal"
observers, but training and practice may reduce
these differences to an acceptable level. If
some important examination is underway, it is
recommended to use more than one observer
and take the mean value of their responses as
a result.

Color Vision Testing
Pseudo-Isochromatic Plates frequently are
used by eye specialists to get an idea of
one’s color efficiency or deficiency. To a
color-deficient person, all the dots in one
or more of the plates will appear similar
or the same—“isochromatic.” To a
person without a color deficiency, some
of the dots will appear dissimilar enough
from the other dots to form a distinct
figure (number) on each of the plates
—“pseudo-isochromatic.”

Light and Its Role in Dental Ceramics
Just as a musician must know the scales,
dentists and ceramists must know the
principles of light. Without scales, there
would be no music; without light, no
colour. To better appreciate the
importance of light in dental ceramics, we
must learn some of its basic
characteristics and how these, when
combined with the physical and chemical
composition of natural teeth, influence
our visual perception of tooth colour.

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Direct Light
When direct light falls upon an object, it is
either absorbed, reflected, or transmitted.
If all of the light is reflected, the object appears
white.
If the light is entirely absorbed, the object
appears black.
The larger the amount of light reflected by an
object, the brighter the object will appear.
Furthermore, the greater the intensity of the
direct light source, the brighter the object will
appear.
The final effect depends greatly on whether the
object is transparent, translucent or opaque.
Teeth and porcelain have all these
characteristics, however the differences in the
chemical and physical properties of teeth and
porcelain require that these characteristics be
treated differently.

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In duplicating tooth colour, we must
produce a ceramic restoration that
captures all the colour dimensions found
in the tooth despite the opacity produced
by the gold and opaque layer, rather than
in conjunction with it. The opacity found
in the dentin is a chemical phenomenon
rather then the physical one produced by
the metal in a ceramic restoration.
Light can be transmitted or passed
through transparent and translucent
substances.
A clear window glass through which an
object can be seen distinctly is an
example of a transparent medium; it
permits maximum transmission of light.

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A frosted glass pane, through which
light is visible but objects are seen
indistinctly, is an example of a
translucent
medium;
it
transmits
diffused light.
A wooden door or brick wall is an
opaque medium and permits no light
transmission
In both natural dentition and fabricated
restorations, we are concerned with
translucent and opaque qualities rather
than transparent ones. Of the three,
teeth have the least transparency; in a
ceramic restoration, this is undesirable
for it serves no constructive purpose

Reflected Light

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Reflected light describes light rays that are
bounced back from the surface of the object
encountered instead of being transmitted through
or absorbed by it.
Light rays that strike the surface of an object are
called incident (falling upon) rays and their point of
contact is termed point of incidence.
Reflected light falls into two categories: specular
and diffused.
Specular light travels in a single direction. When
the incident light strikes a perfectly smooth
surface, it rebounds from the point of impact at
exactly the same angle as the incident ray.
Diffused light travels in more than one direction. If
light rays strike an uneven surface, they cannot be
reflected at an even angle; the incident rays will be
reflected at various angles, making the light
diffused

Color matching and reproduction
Color vision
Color matching is complicated with individual
differences in color perception and different
color matching ability. According to Culipepper
(1970), there are tooth color matching
differences among dentists themselves and it
happens that the same dentist may match
different shades for the same tooth in different
days. Hence, it turns out to be necessary for
dental students, dentists and dental technicians
to undergo a color vision test, particularly in
view of the fact that approximately 8% of men
and 0.5% of women are color deficient (Barna,
1981; Paravina et al., 1997 a).

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Color matching conditions
Tooth color is in the clinical practice matched
under different illuminants. Illumination for
shade matching should be standardized and
harmonized with the laboratory illumination
(Bergen and Mccasland, 1977; Preston et al.,
1978;) While performing tooth color matching,
attention should be attached to the viewing
distance, viewing angle as well as to the impact
of such factors as background and
environment. The color of the patient’s clothes,
the color of the drapes, uniform, equipment,
office furniture, walls and ceiling are of great
importance.

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Dental color standards
Hall (1991) wrote: "Shade guides of all
dental restorative materials are based on
the long established porcelain shade
guides which evolved to represent the
available shades of porcelain teeth. The
shades developed by a process of popular
selection by which shades perceived to be
nearer tooth colour were added and the
least popular eliminated. This concept
has not changed since the introduction of
porcelain over two hundred years ago".

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A number of authorities in dental ceramics point at
inadequacies of the commercial shade guides
(Sproull, 1967; Sorensen and Tores, 1987;
Pizzamiglio, 1991). The shades of the samples are
not logically arranged, they are not equally placed
in color solid and do not cover the color range of
the natural teeth (Hayashi, 1967; Sproull, 1973
b;). The absence of darker shades in the majority
of dental color standards is caused by the
compromise with the cosmetic demands for the
"white" teeth. The samples used for PFM
restoration color matching are made of fired
ceramics, with no metal substrate and the anteriorposterior size of the ceramics is considerably larger
than the ceramic part of the final PFM restoration
(Bergen, 1985. The color of the acrylic resin
samples is changeable if kept in some
disinfectants, particularly in chlorine-containing
disinfecting solutions (Cernavin, 1996).

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The mentioned inadequacies gave rise to
various propositions for the production of
new
shade
guides,
and
for
the
improvement of the sample arrangement
order in the existing color standards, or
resulted in the production of different
individual (custom) shade guides


The manufacturers had ignored for decades the
legitimate demands for the production of new
dental color standards based on the needs of
dental practice, color range of the natural teeth
and the principles of the color science. Certain
progress in this area, however, was made not
so long ago. Vita Zahnfabrik Company (http)
presented a new dental color standard,
"Vitapan 3D Master". This shade guide consists
of 26 samples divided into groups according to
lightness and within those groups according to
saturation (vertically) and hue (horizontally).
Despite the fact that the improvement in
relation to the previous color standard of this
manufacturer (Vita "Lumin Vacuum") is
obvious, certain disharmony in the sample
arrangement can be noticed in shade guide as a
whole.

Color matching method
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It is more than obvious that it is not simple to provide
adequate shade matching conditions. As for the shade
matching method, there have been significant
improvements in this area, especially in the last ten
years.
Shade matching should be performed at the beginning
of the appointment (Sorensen and Tores, 1988;
Pizzamiglio, 1991) and the patient’s mouth should be at
the level of the dentist’s eye. A shade guide sample
should be applied parallel with the tooth whose shade is
being matched, not in front of it, for it will appear
lighter, not behind it because it will appear darker.
Some authors suggest that the cervical part of samples
should be removed because they are more saturated,
which could have a negative effect on the shade
matching (Miller, 1993). Spencer (http) suggests
removal of the mesial and the distal third of the
samples in order to enable application of two shade
guide samples next to the tooth whose color is being
matched.

If the sample and the tooth whose color is being
matched have different surface texture, both should be
wet, in order to neutralize this difference. Tooth should
not be observed for more than five seconds at a time,
and, in the meantime, it is desirable to observe some
blue surface for one minute (Pizzamiglio, 1991) in order
to increase the ability to differentiate yellow color (the
dominant color of the teeth). Owing to possible
occurrence of metamerism, the choice should be
verified under different illuminants. Some authors’
attitude (Seluk and LaLonde, 1985, Swepston and
Miller, 1985) that esthetics can be improved if the
dentist and the dental technician use shade guides and
relative porcelains of several manufacturers is logical
and acceptable. It is also suggested that extended
shade guides should be used (containing the samples of
all ceramic masses used for the production of PFM
restorations), such as Vita "VMK - Shade Indicator"
(Pizzamiglio, 1991; Miller, 1993).

Munsell color order system
Many color order systems are available, but
for a variety of reasons, including worldwide
recognition, consistency, flexibility, and
simplicity, the Munsell Color Order System is
the system of choice for color matching in
dentistry. The attempt to achieve equal
visual (Perceptual) spacing in this system
further recommends it. The color tree (Plate
I) is a representation of the tridimensional
organization of the colors within the Munsell
System. The Munsell color solid can be
likened to a sphere or to a cylinder, as it is an
irregular three dimensional figure that has
characteristics of both.

Although usually described as a sphere
(Munshell’s original concept), for the
purpose of this article, it will be treated a
a cylinder. The relationship of one color t
another becomes apparent when the
organization of the colors within the three
dimensional solid is understood. A
colorless or achromatic axis extends
through the center of the cylinder, pure
white at the top, pure black at the bottom
A series of grays, progressing from black
to white in equal visual steps, connects
these extremities.

Colors (Hues) are arranged around this
axis, and within each Hue, the colors are
arranged in scales according to their
lightness/darkness (Value) and their purity
or strength (Chroma). (In the Munsell
System, Hue Value, and Chroma are
capitalized). Light colors are toward the
top of the cylinder; dark colors are toward
the bottom. The colors are purest on the
outer skin of the cylinder and they become
progressively grayer as they approach the
gray Value axis. Within each of these scales
of Hue, Value, and Chroma, the intervals
were chosen to represent equal visual
spacing under a standard light source.

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 tope of
the cylinder. The hub of each wheel represents the
Value axis. The Hues are arranged sequentially
around the rim. The spokes represent the
gradations of Chroma from the color less axis to
the purest Hues at the rim. In actually, as can be
seen by examining plate I, the Hues project
unevenly beyond the surface of the solid, but this
is one of the advantages of the system. As
technology permits the creation of purer colors,
they can easily to added to the periphery. These
unequal extensions of the Chroma spokes
obviously make some of the wheels flat or
lopsided, but basically we have a cylinder, even if it
is bent out of shape.

value scale


Dimensions of Color.
Hue, Value and Chroma, the dimensions of color, are
just as descriptive in describing color as length, width,
and breadth are in describing form, once the language
is understood by those using it. Since it is so important
in working with color to understand thoroughly the
three dimensional concept of color, a more explicit
description of each is presented.
Hue, Hue: the first dimension, is the easiest to
understand, and in Munsell’s words, “it is that quality
by which we distinguish one color family from another,
as red from yellow, green from blue or purple.” The
color wheel is a familiar form of this dimension and
consists of the Hues that are arranged sequentially
around the central axis of the Munsell color Solid (Plate
II, C). The refer to a Hue in the Munsell system, the
initials are used; R for red, YR for yellow red, Y for
yellow, and so on. Each Hue is subdivided into ten
segments, equally spaced visually (by psychologic
criteria) from each other. The color wheel cut and
placed in a horizontal strip.

Value and Chroma are more difficult to understand
and are often confused with one another. Special
attention must be focused on these dimensions.
Value: Value “is that quality by which we
distinguish a light color from a dark color”, and this
is related to the achromatic (colorless) polar axis
going through the Munsell color solid. The value
of a color is determined by which gray on the Value
scale it matches in lightness/darkness. The black
of the Value scale is assigned a Value of zero, the
white a Value of 10. An infinite number of
gradations of gray is possible as we go from black
to white, but only nine Value (gray) steps are used
in the Munsell system. Pure white (10) and pure
black (0) are unattainable. Fractional numbers are
used when a finer evaluation is needed. “Low”
values refer to dark colors : “high” values to light
colors.

We perceive Value differences when we watch a
black and white television picture. The actual
scene is full of color, but only the
lightness/darkness (Value) of a color is
transmitted, a blue, red or yellow could all be
transmitted as the same indistinguishable gray
if they are of the same Value (a part of the
same Value “wheel’). Colors of high Value
would be transmitted as light grays, and those
of low Value as dark grays, regardless of the
Hue or chroma. It could be said that the Value
of a color is the gray it would match if it were
seen on a black and white television screen.
Tab c in Plate II, B, and all the tabs directly to
its left have the same Value and would,
therefore, transmit as the same
indistinguishable gray.

Chroma : Chroma, the remaining dimension,
“is that quality by which we distinguish a strong
color from a weak one; the departure of a color
sensation from that of white or gray; the
intensity of a distinctive Hue; color intensity.
Chroma describes the amount of Hue in a color.
The gradations of Chroma were referred to as
the spokes of our wheels. The concept of
painting a box will help to clarify this
dimension. Suppose it is desired to paint one
side of box pure red. If an amount of gray
paint is added to the bucket before the second
side is painted, the red on the second side will
be perceived as less than a pure red; the
Chroma will be reduced. If additional gray
paint is added to the bucket before each
additional side is painted, the paint will come
closer and closer to being perceived as a gray.

Plate II, B, is from the Munsell Book of
Color, and studying this illustration will aid
in the understanding of these points. If
the red to the extreme right at Value level
4 (tab c) is considered as the original color
of the paint, the red to the left of this
would represent the paints of reduced
Chroma. Adding a gray always reduces
the Chroma and theoretically will not affect
the Hue. The change in Value of the
original color depends upon the Value of
the gray added to it. If a gray of higher
Value than that of the original color is
used, the resulting color will be of the
same Hue, lessened Chroma, and higher
value (tab a could represent such a result).

If a gray of the same Value is used, only the
Chroma will be affected (lessened). (e.g.,
tab d). If a gray of a lower Value is used,
only the Chroma will be lessened, and the
Value will be lowered (e.g. tab b).
Emphasis is placed on this point in order to
dispel the confusing statements seen in
some dental literature to the effect that
Value depends upon the relative amount of
gray in a Hue and that adding gray always
lowers the Value.
The need to refer to gray in describing both
Value and Chroma is a major factor in the
confusion concerning these two dimensions.
To think of Value in relation to the television
picture and Chroma in relation to the
painting of the box will provide a simple,
easily recalled memory aid.

SURFACE TEXTURE
Matching the surface texture and outline form is an
important as matching the shade of a tooth. This
statement does not diminish the importance of the
shade but emphasizes the importance of reproducing
surface texture and outline form in establishing esthetic
harmony of a ceramic restoration.
Regardless of whether a tooth is flat or irregular, the
surface is viewed as being rough or smooth. A smooth
surface will reflect most of the incident light back to the
observer. A roughened surface randomly scatters the
reflection of light in many different directions. In the
process of determining the character of light reflection,
the surface texture of a crown must be designed to
simulate the reflectance pattern of adjacent teeth.
Properly blending the effects of light reflection and
absorption in a crown creates a natural appearance that
hides slight color differences.

Many dentists have discussed the manipulation
of surface texture to conceal color differences in
ceramic restorations. Obregon et al, found that
increased roughness of porcelain samples
decreased the Value level. Burk, in a pilot
study, observed that modifying surface texture
altered the appearance of porcelain in terms of
Hue, Value, and Chroma, and even affected the
degree of translucency.
On eruption, teeth have their roughest surface
texture. Undulating vertical ridges are formed
by the fusion of developmental lobes
transversed by fine horizontal lines.
These numerous small transverse lines on the
surface of enamel are perikymata produced
during the incremental formation of enamel. In
general, with advancing age these surface
features are gradually obliterated through
attrition from tooth brushing or occlusal wear.

This process of progressive enamel wear
corresponding with advancing age can be
characterized. Through many years of
brushing and the process of natural
abrasion, the lines become less defined
and the tooth surface acquires more
stippled appearance. As the wear
process continues into the later years of
life, all signs of the perikymata are lost
and only the gentle undulations of the
developmental lobes are observed.
Finally, the definition of the
developmental lobes is obliterated and
the tooth appears smooth with a highly
reflecting glassy surface.

The teeth with a highly reflectively glassy
surface. The teeth of a younger
individual will most likely have the
perikymata and developmental lobes
intact. Emulating the surface
characteristic for a particular age group
facilitates achievement of a life like
restoration. Failure to reproduce surface
detail accurately will result in light
reflection different from that of the contra
lateral teeth. This result will suggest
artificially, despite correct color and
contour matching.

To create the surface texture of a young individual, the
developmental lobes and vertical undulations are first
defined with a cone shaped diamond bur. Next, a
rotating football shaped diamond bur moved
mesiodistally defines perikymata. The crown is fired to
a light autoglaze to hear surface flaws. Finally,
diamond polishing paste on a 1 inch felt wheel creates
the desired surface shine.
The smooth surface of an older tooth resulting from
heavy abrasion, is first prepared by defining any
developmental lobes. Ridges and heights of contour are
polished with a rubber wheel. The crown is held at
glazing temperature for a longer period to achieve a
smoother autoglaze. The final finish is accomplished by
polishing with Brasso cleaner (French Household
products, Rochester, N.Y.) and pumice on a high speed
lathe with a large felt wheel to the desired smoothness.
Wear facets can be www.indiandentalacademy.com
created by further selective
polishing with a rubber wheel.

Although study casts are helpful in demonstrating
major features such as developmental ridges, surface
texture is inadequately reproduced by a stone cast.
The use of a resin replica has been suggested for better
reproduction of surface detail.
A tooth tab actually demonstrating surface texture
provides much more detail than a written prescription
or a study cast. We have developed a system of using
extracted teeth with varying degrees of surface texture.
The teeth are sterilized, numbered for easy
identification, and retained on a ring. By having
several sets of surface texture tabs available, the
dentist match and record the appropriate surface
texture tab and include the tab with the preparation
dies. Preparation of various surface texture on porcelain
tabs is an alternative to the use of extracted teeth.
The identification tab, which will be discussed, can also
be textured for communication with the ceramist. The
identification tabs can be prepared with a range of
surface texture and degrees of luster.

Although final chairside
adjustment is always
necessary, the ceramic
restoration produced by
the ceramist will require
less adjustment and be
closer to the desired
finished result. Because
the surface texture of the
crown is similar to that
the natural teeth to be
matched, it allows rapid
evaluation of suitability of
color match.

SHADE SELECTION PROCEDURE:
CLARK SAID, "Color, like form, has three dimensions,
but they are not in general use. Many of us have not
been taught neither names, nor the scales of their
measurement. In other words, we as dentists are not
educationally equipped to approach a color problem."
This statement is, unfortunately, still true. Dentists
have had little or no training in vision physiology or
color science. A 1967 survey revealed that 23 out of
112 dental schools had some sort of color education in
their curriculum. A survey conducted the following
year, reported that 3 of 115 dental schools taught a
formal course in color. Thirty years later,
comprehensive color training continues to be a missing
part in the dental school curriculum. If any training at
all is given in dental school, it is cursory or simplistic
and usually consists of presenting an incomplete
explanation of three abstract concepts of the Munsell
Notation:4 hue, value and chroma.

The increase in newer types of ceramic
restorations and the improving quality of
esthetics means the dentist of the 21st century
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 then be able to make any necessary
adjustments to the restoration. However, there
are a number of factors that stand in the way
of properly selecting a color match. Subjective
faults range from differences in color perception
to ocular fatigue and lack of education
regarding the basic principles of color.
Metamerism may occur if proper lighting is not
used during shade selection in the dental office
and laboratory Finally, existing shade guides
are limited and require a more extensive range
of shades.

Therefore, it is no surprise that color matching for crowns
and dentures can be a frustrating and discouraging
experience for the dentist, technician and patient. The
breakdown in communication over matters ranging from
shade guide to laboratory prescriptions must be
addressed. This study will review the problems of color
matching and will attempt to guide the reader toward
enhancing his or her techniques regarding shade selection
and communication with the ceramist.
Tooth vs. Porcelain
Prior to shade matching, the dentist must have an
understanding that the human tooth and dental porcelain
transmit light waves differently It is their physical
composition that determines the differences in light-wave
transmission, absorption, reflection, refraction, scattering
and surface gloss. The manner in which light strikes an
object determines the total appearance of the material.
Transparent materials allow for the passage of light with
little change. Translucent materials scatter, transmit and
absorb light. Opaque materials reflect and absorb;
however they do not transmit. Surface characteristics,
such as gloss, curvature and texture, will affect the
degree of light diffusion when striking the particular object.

A vital tooth is both naturally translucent and
transparent. Enamel rods are transparent and therefore
refract and reflect light. Light that strikes the incisal
edges of an anterior tooth passes through with
maximum transmission because of a high degree of
translucency.
Porcelain, however, is a heterogeneous material. It
contains transparent properties and metallic oxides that
act as opacifiers. These porcelains modify light by
absorption, transmission and reflection. Absorption is
largely responsible for color. It occurs when light
passes through the layers of the porcelain. Scattering
occurs when light encounters interfaces between the
materials (i.e., pigments and glass). The smaller the
pigment size, the less light that is absorbed, resulting
in less detectable color. The larger the pigment size,
the more reflection that occurs as light scatters at the
particle surfaces. Scattering light is necessary in dental
porcelains to simulate the prismatic effect of enamel.
Yet, one must keep in mind that too much dispersed
reflection through internal scattering will create an
unnatural looking prosthesis.

Light Sources
One of the questions asked when
selecting a shade is, what light source
should be used? Shade determination
should be performed under color
corrected fluorescent lighting, which
contains a balance of the entire visible
spectrum. The operatory should be lit
using a luminous ceiling with translucent
diffusing panels that are simple to
maintain. Clean watt saver lamps having
a color temperature of 4200K or higher is
advocated. Shade selection should not be
made using daylight, because daylight is
subject to constant changes.

One must also be concerned with the phenomenon of
metamerism, which occurs when the color of two
objects looks identical when observed under one light
source but different under other light
conditions.Metamerism occurs only when two objects
have different wavelength distribution and therefore
reflect different spectra.
The color of the operatory can also affect shade
selection. Colors should be kept at a low saturation
level. Walls and cabinets should be glossy enough to
maintain brightness without causing a glare. It is
recommended that the color of the walls and ceiling be
white or off-white.
The dentist should be concerned with "blue fatigue:'
this occurs when the eye is unable to differentiate
between the various shades of blue. However, blue
fatigue increases sensitivity to yellow therefore, to
improve shade selection in the yellow range, the
operator should stare at a blue card or patient napkin
between shade comparisons.

It has been suggested that dentists use
natural north daylight for shade
matching. Many dental offices have been
designed to face the north to enhance the
selection process. However, daylight is
not at a constant throughout the day and
therefore must not be used as the only
light source for shade matching.


The Problem with Shade Guides
Shade guides have become the standard for selecting
shade, yet there have been many errors associated
with the use of commercial shade guides. Problems that
may arise include the following:
1. Porcelains do not match the shade guides that they
are being compared to.
2. Shade variations occur between different die lots of
porcelain from the same manufacturer.
3. Shade guide tabs are 4-5 mm thick compared to the
thin 1.5 mm piece of porcelain used for the restoration.
4. Shade guides are not always made with fluorescent
porcelain, which causes inconsistencies in color
matching.
5. It is difficult to predict the final shade after the
layering of opaque, dentin and enamel.
6. Guide tabs lack a metal backing when using
porcelain-fused to-metal restorations.
7. Shade tabs are condensed differently than porcelain
used for final restorations.

Now that the reader understands the
potential problems that arise when
selecting shade, it is imperative that the
dentist have a proper education in color.
However, we must assume that not every
dentist will seek out the proper courses.
The latter portion of this article will be a
review of numerous methods for
enhancing laboratory communication
between the dentist and the dental
technician, to assure the success of
proper shade matching. The dentist must
then decide for himself or herself how
much information is enough to guarantee
the replication of the restored teeth.

Shade Selection Guidelines
The dentist must have a working knowledge of
the basic principles of color. This allows for
accurate shade selection. Munsell described the
three dimensions of color as hue, value and
chroma.
Hue is the property of color that is determined
by wavelength, which distinguishes one color
from another. Value is a quantity of brightness.
It is a qualitative term related to lightness or
blackness of color and not the quantity of the
color gray Chroma is the saturation of color.
Matching the proper shade is not carried out
just by holding up a guide tab to the tooth in
question. There are a number of methods that
can be employed to intensify the shade
selection. They are as follows:

1. If patient is wearing bright clothing, drape him or her
with a neutral colored cover.
2. Have patient remove lipstick or other make-up.
3. Clean the teeth and remove all stains and debris.
4. Have patient's mouth at dentist's eye level.
5. Determine shade at the beginning of the appointment
to avoid ocular fatigue.
6. Shade comparisons should be performed at five-second
intervals so as not to fatigue the cone cells of the
retina.
7. Obtain value levels by squinting.
8. Compare shade under varying conditions (i.e., wet vs.
dry lips; retracted lip vs. pulled down lip).
9. Use the canine as a reference for shade because of the
highest chroma of the dominant hue of the teeth."
10. If unable to precisely match shade, select a shade of
lower chroma and higher value.
11. Grind off the necks of the shade tabs because they
tend to be darker than the rest of the shade tab.

Custom Shade Guides
To properly start the shade matching process
the dentist should acquire a custom shade
guide. This guide is the beginning of improving
communication with the laboratory Each
custom shade guide should include the
ceramists metal, porcelain, staining kits,
equipment and techniques. It should also
contain pointers as to what to look for when
selecting a shade. The technician needs to send
a chart along with the guide for jotting down
any additional information that will allow for a
better understanding of the particular shade.
The dentist may choose to create a luster tab
and send it to the laboratory with the
prescription. The technician will then have a
visual aid for what he must fabricate.
Numerous techniques regarding custom shade
guides have been noted in the literature.

Procedure for shade selection:
The first step is to select the hue .this is a delicate step
since thereis not much difference among the hues
.because different chromas of the same hue are close
to each other in the manufacturers arrangement of the
shade guide there can be confusion.for this reason
pizzamiglio used “the four hues technique”. In the vita
shade guide there are only four hues ,A B C andD. The
maximum chromas of each hue A4,B4,C4,andD4 are
removed from the shade guide and put in a vita VMKindividualskala kit . this allows one to visualize the
difference in hue more effectively because chroma is
more intense . the lamp is set at a distance of 20cm
from the dental arch and, with the shade guide
arranged with the four hues ,two passes from the
beginning to the end of the guide are quickly made
close to the teeth . it is important to determine the hue
by observing the shade guide against the cervical part
of the tooth .

Looking toward the cervical part increases the
perceived chroma where as looking toward the
incisal part decreases the perceived chroma
,making it more difficult to distinguish the hues.
When the canine is present ,it is the best tooth
on which to choose hue because it has the
highest chroma. This step should be performed
within 5 sec,otherwise the ability to recognize
the desired hue decreases . the eyes are then
rested by gazing at a blue background.
Suppose that the hue chosen is A. once this is
done the other three hues (B,CandD) are set
aside .next all of the different chromas of the
selected hue are put in the Vita VMKIndividualskakala kit .an example that would be
A1,A2,A3,A3.5andA4. At this point we have
different chromas of the selected Hue in the
shade guide to match with the tooth.

Again working quickly(less than 5 sec),the
dentist selects the chroma by comparing the
shade guide against the tooth . This is much
easier because now we have only different
chromas chromas of the same hue , the eyes
are rested by gazing at a blue background for 1
min . Suppose that the selected chroma is A2.
Through the shade indicator chart .,we know
the number of the dentin (in the case of A1, it
is 541). The chroma is again checked with a
ring arranged by the dentin colour .it is of the
necessary to make corrections . the number of
the dentin chroma that has been chosen is
recorded. The blue background is again used to
rest the eyes . Next the enamel is chosen with
enamel colours . in this case the observation
should be done at the incisal part of the teeth
where the enamel is thicker .

The second shade guide arranged according to
the value , is used to select the value. An
important part of this procedure is to squint the
eyes . squinting causes the black and white
sensitive rods in the eye to become more active
than the colour sensitive cones. The rods are
responsible for helping to determine the value.
It is important to avoid consideration of the hue
and chroma when selecting the value. The
value that has been selected is used to choose
the opaque porcelain. If the value is wrong ,the
effect will be particularly unpleasant in the
cervical region where the thickness of PFM is
less.

Shade Guides
Because an important factor in restorations is the shade
determination, it is imperative that guides are available
to assist in the correct shade matching.
VITA Lumin Vacuum Shade Guide contains porcelains
that are pre-fired set out in the colour tones that the
company has available. They are arranged on porcelain
pins that can be removed individually for maximum
shade matching. The main tones groups are rosebrown, rose-white, greytone, and rose-grey.
VITA VMK Individualised Shade Guide is a kit for the
reproduction of intermediate and individual shades, and
therefore demonstrates the offering of a multitude of
possibilities of shade determination of the companies
metal ceramics. This is the main communication
method of shade determination between dentist and
technician. The porcelains are layered onto a ceramic
cap which corresponds in colour to the oxidised metal.
These are also excellent for practice.

How do you determine the tooth shade with VITAPAN
3D-MASTER?
The logical configuration of the shades makes working
with
VITAPAN 3D-MASTER very easy.
The shade selection is a logical progression of three
simplified choices - the desired shade is found very
quickly:In the first step of the shade taking procedure
the value (lightness) is determined. Select the value
level from the five value groups (levels 1 - 5) that is
closest to the value of the tooth to be compared. Pull
out the medium shade sample (M) from the selected
value group.

In the second step the chroma (levels 1 2,3)
is determined. Select the color sample of the
selected M group that is closest to the tooth to be
compared. In the third step the hue (L, M, R) is
determined. Check whether the natural tooth
displays a "more yellowish" (L) or "more reddish"
{R) shade than the color sample of the M-group
that has been selected in the second step. Now the
best matching shade sample is determined and the
information is recorded in the color communication
form.


VITAPAN 3D-MASTER divides the tooth color space into 5 levels of value.


In the medium (M) hue there are three levels of color samples for
the chroma. Deviations towards the more yellowish hues (L) or more
reddish hues (R) exist in 2 chromas.


A deviation of the medium hue (M) towards yellow or red can be
compared with the corresponding hue groups (L,


Value (lightness) level
In the first step the value or lightness is determined.


Chroma
In the second step the chroma or color saturation
is determined.


Hue
In the third step the hue is verified.


Opaque Porcelain.
Success in duplicating depends greatly on
proper opaquing procedures. Reproduction of
the colour tone of natural teeth is attainable
with an understanding of opaque porcelain. The
opaque layer is the foundation of the ceramic
portion of a porcelain fused to metal
restoration. This foundation provides an
excellent bond and consistent and precise
shade control. Opaque should be mixed with
Condenser Liquid or distilled water to the
consistency of heavy cream, which can be
easily applied with brush or spatula. The
preferable method of applying opaque is with
two thin coats, fired individually to a total
thickness of 0.2 - 0.3 mm. Opaque porcelain
should never be allowed to dry in application

Opaque
porcelain
It masks the
metal colour.
Because teeth are
translucent the
body porcelain is
made
transparent, so
the opaque
porcelain is used
to mask the
metal colour.





Success of the
application of
opaque depends
of following 3
working
techniques:
brushing
moisture control
condensation of
the opaque
porcelain by
vibration or other
methods

Liquids - Opaque, Modelling & Condenser
 Opaque liquid is used for mixing and
remoistening of opaque porcelains
 Modelling liquids are used for mixing all dentine
and enamel porcelains.
 The use of Condenser Liquid, which is in effect
a stronger form of modelling liquid, allows the
porcelain to stay wet longer, resulting in more
working time. It is ideal for larger restorations.
It improves stability and considerably extends
working time. Some generic condenser liquids,
when used with opaque powders, will result in a
pastier consistency, yielding a greater ease of
application

Dentine Porcelain
Dentine is used to build the dental
shape. It gives the opacity and the
density of the natural tooth dentin to the
porcelain, for use in the anatomical
shading.
These are the components for the build
up of the crown. These are used to build
up the tooth after the opaque firing.
The definite shape of the tooth is
constructed with dentine materials.
Dentine can be mixed with stains. .

Enamel Porcelains
Also known as incisal porcelains.
Display a degree of opalescence that makes it comparable to
natural tooth definition.
Acts as a transmitter of the underlying colour found in the
dentine and is made up of long rods that are surrounded by
a prismatic substance and are perpendicular to the dentin.
It is this fibre-optic arrangement that permits light to pass
through the enamel, strike the underlying colour in the
dentin and reflect off in all directions giving the opalescent
appearance mentioned above.
Can be applied with the dentin or separately after the dentin
has been fired.
Translucency of the natural enamel (in true teeth) increases
with age, and therefore with age the natural tooth appears
more transparent. So an understanding of the role of
enamel porcelain, as well as the body and colour of the
restoration, is of vital importance.
It should be applied in several small portions to complete
the shape of the crown or the occlusal surface. It should be
modelled slightly larger than the actual tooth size to allow
for shrinkage when fired.

Ceramic Stains
Ceramic stains should be used sparingly
as they are designed to supplement the
characterisations already inserted into
the restoration.
Stains can be used to create root
attachments, enhance the overall
shaping, simulate fillings and imitate
tobacco and tea stains.
Stains can be used to alter shades and to
add characterisation. They can be applied
and baked separately or can be baked
concurrently with glazes.

Cervical or Marginal Porcelains
When working in metal ceramics, it is often
found rather difficult to achieve satisfactory
results for the cervix of the tooth. Even with a
shoulder preparation, metal will still be visible
as a dark rim, which will have an obtrusive and
unaesthetic effect in the mouth.
These materials are layered onto the dentine
above the neck of the tooth extending into the
approximal area to increase the illusion of
depth.
They are usually special dentine porcelains with
a higher stability, that assists in achieving
maximum marginal fit.
They can also be used in corrections





Glazes
Are used to apply a
soft, silky shine to the
restoration
Either high or low
fusing glaze may be
used as a last step,
providing a high gloss
finish to all ceramic
restorations.


Laboratory Prescriptions
With few exceptions, laboratory work
authorizations do not request enough
information from the dentist. This could
be because there is not enough space on
the prescription to record it. It is,
therefore, important to use a laboratory
that fully understands the need for shade
matching. Each laboratory prescription
should contain enough space to record
clinical information about each ceramic
component of the restoration-for
example, different shades of porcelain
and opaque, and where to place them on
the tooth.

The authorization should include
numerous diagrams of the tooth so that
the dentist can draw helpful notes on
them (i.e., shade, translucency, staining,
glaze and surface texture). And the
dentist should be in contact with the
ceramist to ensure that the technician
fully understands what the dentist is
requesting. It is through these methods
that the dentist builds a relationship with
the technician. Ceramists will usually
return the quality that the dentist sends
to them.15

Models
Along with the laboratory prescription,
the technician should have a set of study
models to use as a guide. Preoperative
models give the ceramist information
about occlusion, tooth alignment, position
of soft tissue, diastema, surface texture,
wear facets, and more.16 A diagnostic
wax-up will aid in the occlusion and form
of the restoration. Matching shade is
obviously only part of the task of
replicating the natural tooth.

Photography
The macro lens has become an important
tool in communicating with the
laboratory. It has been said that, "The
photograph is the cosmetic dentist's
radiograph.this enables the technician to
evaluate the color of a particular tooth,
see craze lines, stains, surface texture
and luster. Multiple pictures should be
taken at different angles and under
different light sources. The patient's
occlusion should also be photographed.

Along with photographs of the teeth being
worked on, it is best to include pictures of
the patient's smile. These photographs
can tell the technician about the patient,
his or her age, personality and character.
It is a good idea to photograph the
prosthesis at the try-in stage. If color
adjustments are necessary, the
technician will have a visual aid to help
make the proper corrections. Written
instructions alone are not enough
information for the technician. They leave
a tremendous amount of room for
interpretation.

Computers
Computers have become a valuable
communications tool for the dentist and
laboratory Cosmetic imaging can take the place
of photographs. The dentist can take a picture
with an intraoral camera and send it over the
Internet to the laboratory. Film developing is
eliminated, saving time and money. The
ceramist can use these images to fabricate the
proper prosthesis.
E-mail can be sent between dentist and
laboratory to facilitate discussions of shade
matching. The ceramist may decide to offer
suggestions to the dentist based on the original
images sent over the computer. E-mail can be
used if the dentist is busy with a patient and
cannot come to the telephone.

Computed Color Matching:
Every dentist who places esthetic
restorations has at one time or another
been frustrated by the process of trying
to match the color of natural teeth with
ceramic
or
resin
restorations.
Conventional shade guides have severe
limitations, both in design and in product
execution. Even the latest iterations of
shade selection systems do not cover the
dental shade range. It would seem that in
today's highly technical world we should
be able to develop a computer-based
shade selection device.

After all, there are spectrophotometers at
the local paint store and automobile paint
shops use a spectrophotometer for your
car repair. Why doesn't the dentist have
one for shade selection? Unfortunately,
the dental color measurement problem is
very complex. It has been said that the
dental shade selection problem is the
most difficult of all color measurement
situations. Teeth have every difficulty
that can be encountered: they fluoresce,
are inhomogeneous and translucent, and
have small, irregular surfaces.

In the past, several devices have
attempted to solve the instrumental
approach to dental color measurement.
All failed. Today there are several devices
that are presently, or soon will be,
offered to the dental profession. "Pikkio",
a development of a Swiss and Italian
venture, briefly entered the marketplace
and is currently being refined.


It is a hand-held unit that can be
downloaded to a computer. The device
gives the user the closest Vita® shade
guide, and the amount by which the
tooth varies from it.: Wolf Industries of
Vancouver, will soon market a device that
provides the nearest match to both the
Vita® and Ivoclar® shade guide, and the
amount by which the tooth differs from
the guide


Shofu Dental Corporation is said to be
ready to offer a device researched by the
group at Iwate University in Japan. The
exact software behind this device has not
been released as of this writing. The
appearance of multiple devices attempting
to solve this problem is testimony that the
scientific community recognizes the need
for assistance in dental shade selection,
and the willingness to underwrite the
development of a solution. In addition to
the devices cited, several others are
known to be under development.

Certainly, most restorative dentists
would welcome reliable technical
support in shade selection and color
matching. However, the device would
be most helpful if it not only correctly
analyzed the tooth color, but also the
optical properties such as
translucency and surface gloss.
Restorative materials correlated to
these readings should then be
developed to optimize predictable
results.

Review of literature
1. Sproull, Robert C. in the year 1973 did a study
to explore the 3D nature of color and the correct
terminology.He explained the MUNSELL COLOR ORDER
SYSTEM
It’s a 3D color tree, described as a sphere or cylinder.
It could be considered as a series of wheels stacked
one upon the other, in order of ascending lightness. A
colorless axis extends through the center of the sphere,
pure white at the top, and pure black at the bottom. A
series of grays connect the extremities. The three
dimensions are:
1. Color (Hue)= arranged around the axis, and
subdivided in ten segments.
2. Value= lightness or darkness, within each hue,
arranged in scales.
3. Chroma= purity of strength. The quality by which we
distinguish a strong color from a weak one.

2. Sproull, Robert C. in the year 1973 also studied
the requirements for a color shade guide. He said that
the ideal color space is one in which each color is the
center of a sphere of color, and the closest match
surrounds it.
COLOR SPACE OF THE NATURAL TEETH AND SHADE
GUIDES: Different studies performed by Hayashi and
Clark using natural teeth , measured the ranges of Hue,
Value and Chroma of natural teeth. The ranges of the
Hayashi study and the spectrophotometer were used
for the article.
Available shade guides do not extend through the
volume of color space and lack order or relationship
between tabs. There is duplication of color and voids of
color in other areas of color space.He concluded that
increased research on color problems should be
encouraged. Shade guides should be based on the
Hayashi and Clark type guides ,and porcelain should be
developed to match these guides.

3. Sproull, Robert C. in 1974. discuseed the
perception of color and metamerism
A. Perception of color
1. Light source ; incandescent, noon and average
daylight.
2. Surface viewed- accomplished with a
spectrophotometer, breaks down a standard light source
into a series of sequential monochromatic beams.
3. Individual observer.
4. Final perception- modification of the message by the
eye of the individual, creating stimulus which the brain
converts into color perception.
B. Metamerism: Defined as invisible spectral differences.
Dependent upon:
1. Control-knowledge of metamerism, reduces potential
disasters.
2. Surface viewed- dependency upon the manufacturer
to use correct pigments, to simulate enamel.
3. Individual observer-elusive, since the dentist can
have color vision deficiencies.
4. Light source- color match should be done under at
least two sources of light.

4. Donahue J., Goodkind R., et al. 1991
did a study on Shade Color Discrimination
By Men And Women. And concluded that
Women do not agree with one another more
than men in shade selection. No particular light
source and shade guide improved agreement
for men. Vita Lumin light source increased
agreement with women. When a patient's teeth
are to be matched with a given shade guide,
there is no reason to select the clinicians
according to gender; rather, clinicians should
be screened for color vision.


5. Preston J.D., Ward l.C. and Mitchell B 1978.
explained the importance of Light and lighting in
the dental office.
GENERAL CONSIDERATIONS:
Visual Task: Define what is to be accomplished in the
particular area, and determine what amount of light is
required.
Blocking Shadows: Sufficient ambient lighting to reduce
shadowing.
Difference in Brightness: The ideal ratio of task
illumination to room illumination is 3:1.
Glare: Excess light.
Veiling Reflections: When a glossy surface is
illuminated, reflected light may obscure the viewer's
perception of the surface.
Pleasantness: Sometimes an area may be illuminated
for the specific purpose of being a pleasant place to
pass time.

Age of the Viewer: As age advances more light is
required to accomplish a task.
Light and Heat: The fluorescent fixture is much more
effective than the incandescent but still produces a
large quantity of heat in the effort to emit light.
Cost: The higher the lumens per watt, the lower the
cost of the overall lighting. Lamps will last longer if
burned with only one start per user day and are not
turned off and on unnecessarily.
DENTAL OFFICE AREAS:
Reception: Conveys personality of the office. Decrease
anxiety by lowering levels of illumination.
Office: Ample illumination to ensure effective and
efficient work.
Operatory: Use fiberoptics. Place lighting units parallel
to the work area and out off the direct line of the
patients sight. 5500o K is best for color matching. 200
to 300 foot candles (fc) recommended light level for
operatory.
Powder Room: Incandescent with a pink hue works
well, but this light may not exhibit the best color match
of a "new" dental restoration

6. Barna, G.J., et al. 1981did a study To determine the

effect of various batches of porcelain on the shade of
three porcelain-bonded-to-metal systems and concluded
that:

1. No color differences were found among specimens of
individual batches.
2. Discerning color changes were observed among three
batches of one brand of porcelain.
3. The porcelain fired in the laboratory may not match the
manufacturer's standard shade guide.
4. Batch to batch variation of porcelain may necessitate
the fabrication of customized shade tabs with fresh
batches of porcelain.
7. Barna, G.J., et al . 1981 Did a study on The
Influence of Selected Light Intensities on Color
Perception Within the Color Range of Natural Teeth .
and concluded that the Intensity of office illumination is
not critical for matching tooth shades. It is recommended
that color corrected bulbs be used to allow the full
spectrum of color to be seen. Neither the specialty of the
dentist or time in practice appeared to be a factor in
making color discrimination.

8.Billmeyer and Satzman 1966 defined color

as the result of the physical modification of light
by colorants as observed by the human eye and
interpreted by the brain.

9. Culpepper 1970 Concluded from 36
practising dentists who were invited to match the
shades of 6 natural teeth using 4 shade guides &
4 different light sources , including daylight that:
There was a lack in consistency between the
individual dentists participating in the
experiments in matching natural tooth shades .
The shade guides employed in the study did not
always correspond to the gradations of
predominant colors observed in the natural teeth
Critical color perception varied from individual to
other .


CONCLUSION:
CLARK SAID, "Color, like form, has three dimensions,
but they are not in general use. Many of us have not
been taught neither names, nor the scales of their
measurement. In other words, we as dentists are not
educationally equipped to approach a color problem."
The increase in newer types of ceramic restorations and
the improving quality of esthetics means the dentist of
the 21st century 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 then be able to
make any necessary adjustments to the restoration.
However, there are a number of factors that stand in
the way of properly selecting a color match. Subjective
faults range from differences in color perception to
ocular fatigue and lack of education regarding the basic
principles of color. Metamerism may occur if proper
lighting is not used during shade selection in the dental
office and laboratorywww.indiandentalacademy.com
Finally, existing shade guides are
limited and require a more extensive range of shades.

Therefore, it is no surprise that color matching
for crowns and dentures can be a frustrating
and discouraging experience for the dentist,
technician and patient. The breakdown in
communication over matters ranging from
shade guide to laboratory prescriptions must be
addressed.
An understanding of the science of colour and
colour perception is important for the success
of an esthetic restoration . for sucessful
application of colour in dentistry an
understanding of how light is interpreted as
colour is important . errors in shade matching
continue to be a problem and a source of
dissatisfaction for the patient . inspite of the
limitations in materials and techniques , a
harmonius restoration can almost always be
achieved if a methodical and organised manner
is followed during shade selection.

REFERENCES
1. Sproull, R. C. Color matching in dentistry.
a. Part I: The three dimensional nature of color. J
Prosthet Dent 29:416-423, 1973.
b. Part II:
Practical applications of the organization of color. J
Prosthet Dent 29:556-566, 1973.
c. Part III: Color control. J Prosthet Dent 31:146-154,
1974.
2. Donahue, J.L. et al.
Shade color discrimination by men and women. J
Prosthet Dent 65:699-703, 1991.
3. Presswood, R. G.
Esthetics and color: Perceiving the problem. DCNA
21:823-829, 1977.
4. Preston, J. D., Ward, L. C. and Mitchell, B. Light and
lighting in the dental office. DCNA 22:43l-451, 1978.
5. Barna, G. J., et al.
The influence of selected light intensities on color percept
percep
. J Prosthet Dent 46:450-453, 1981.
6. Obregon, A., Goodkind, R. J. and Schwabacher, W.

7. Schwabacher, W.B and Goodkind, R.J.
Three dimensional color coordinates of natural teeth compared with
. J Prosthet Dent 64:425-431, 1990.
8. O'Brien, W.J. et al. Coverage errors of two shade guides. Int J
Pros 4:45-50, 1992.
9. Barghi, N., Pedrero, J. A. F. and Bosch, R. B.
Effects of batch variation on shade of dental porcelain . J Prosthet
Dent 54:625-627, 1985.
10. Goldstein, R. E. Esthetic principles for ceramometal
restorations. DCNA 21:803-822, 1977.
11. Barghi, N. and Goldberg, J. Porcelain shade stability after
repeated firing. J Prosthet Dent 37:173-175, 1977.
12. Jacobs, et al. Effect of porcelain thickness and type of metalceramic alloy on color. J Prosthet Dent 57:138-145, 1987.
13. Sorensen J. A. Improved color matching of metal-ceramic
restorations.
a. Part I: A systematic method for shade determination. J
Prosthet Dent 58:133-139, 1987.
b. Part II: Procedures for visual communication. J Prosthet Dent
58:669-677, 1987.
c. Part III: Innovations in porcelain application. J Prosthet Dent
59:1-7, 1988.
14. Rosensteil, S.F. and Johnston, W.M. The effects of
manipulative variables on the color of ceramic metal restorations.
J Prosthet Dent 60:297-303, 1988.

15. Barghi, N. and Richardson, J. T. A study of various factors
influencing shade of bonded porcelain. J Prosthet Dent 39:282284, 1978.
16. Albino J. E., Tedesco L. A., Conny D. J., Patient perceptions
of dental-facial esthetics: Shared concerns in orthodontics and
prosthodontics, J. Prosthet. Dent. 52: 9-13, 1984.
17. Barghi N., Alexander L., Draugn R. A., When to glaze - An
electron microscope study, J. Prosthet. Dent. 35: 648, 1976.
18. Barghi N., Color and glaze: Effects of repeated firings, J.
Prosthet. Dent. 47: 393-395, 1982.
19.Crispin B. J., Hewlett E., Seghi R. R., Relative color stability
of ceramic stains subjected to glazing temperatures, J. Prosthet.
Dent. 66: 20-23, 1991.
20.Culipepper W. D. A comparative study of shade-matching
procedures. J. Prosthet. Dent. 24: 166-173, 1970
21.Ishikawa-Nagai S., Sato R., Shiriashi A., Ishibashi K., Using a
Computer Color-Matching system in color reproduction of
porcelain restorations. Part III: A newly developed
spectrophotometer designed for clinical application, Int. J.
Prosthodont. 7: 50-55, 1994
22.Ishikawa-Nagai S., Sawafuji F., Tsuchitoi H., Sato R.,
Ishibashi K., Using a Computer Color-Matching System in color
reproduction of porcelain restorations. Part II: Color
reproduction of stratiform-layered porcelain samples, Int. J.
Prosthodont. 6: 522-527, 1993 a

23.Seghi R. R., Johnston W. M., O’Brien
W. J., Performance assessment of
colorimetric devices on dental porcelains,
J. Prosthet. Dent. 68: 1755-1759, 1989
(b).
24.Seghi R. R., Johnston W. M., O’Brien
W. J., Spectrophotometric analysis of
color differences between porcelain
systems, J. Prosthet. Dent. 56: 35-40,
1986 (a).


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