Shade selection/ orthodontics training courses

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

 History of theories in colour vision
 Description of colour – different systems
 Shade selection
› Visual shade selection (lighting & vision)
 Shade selection systems
› Instrumental colour analysis

An understanding of the process in
which the colour and translucency of
restorations are planned and obtained
so as to replicate the colour and
contours of its adjacent teeth is
important for achieving an esthetic
restoration.
Errors, especially in the colour
replication process, have been a
problem and a source of frustration for
the clinician and technician, thereby
leading to dissatisfaction to the patient.

 Although Aristotle and other ancient
scientists had already written on the nature
of light and colour vision, it was not until
Newton that light was identified as the
source of the colour sensation.
 In 1801 Thomas Young proposed his
trichromatic theory, based on the
observation that any colour could be
matched with a combination of three lights.
This theory was later refined by James Clerk
Maxwell and Hermann von Helmholtz.
 In 1810, Goethe published his
comprehensive Theory of Colours.

 At the same time as Helmholtz, Ewald
Hering developed the opponent process
theory of colour, noting that colour
blindness and afterimages typically come in
opponent pairs (red-green, blue-yellow,
and black-white).
 Ultimately these two theories were
synthesized in 1957 by Hurvich and
Jameson, who showed that retinal
processing corresponds to the trichromatic
theory, while processing at the level of the
lateral geniculate nucleus corresponds to
the opponent theory.

 Professor Albert H. Munsell in the
first decade of the 20th century
developed the Munsell Colour
System
 Several earlier colour order
systems had placed colours into a
three dimensional colour solid of
one form or another, but Munsell
was the first to separate hue,
value, and chroma into
perceptually uniform and
independent dimensions, and
was the first to systematically
illustrate the colours in three
dimensional space.

 In 1931, an international group of experts
known as the Commission Internationale
d'Eclairage (CIE) developed a mathematical
colour model, which mapped out the space of
observable colours and assigned a set of three
numbers to each.
 Latest colour system:
Published in 2002 by the CIE Technical
Committee 8-01 (Colour Appearance
Modelling for Colour Management Systems), as
of 2008 CIECAM02 is the most recent colour
appearance model ratified by the CIE, and the
successor of CIECAM97s.

 Just as a solid is described in three axes of
physical form, colour has three primary
attributes that allow it to be described with
precision.
 Colour is a phenomenon of light or visual
perception that permits the differentiation
of otherwise identical objects.
 There are three factors upon which colour is
dependent:
1. The observer,
2. The object, and
3. The light source.
Herbert T. Shillingburg, Jr., Sumiya Hobo, Lowell D. Whitsett, Richard Jacobi, Susan E. Brackett.
Fundamentals of Fixed Prosthodontics.www.indiandentalacademy.com

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. Color is usually
determined visually by measurement of hue,
saturation, and luminous reflectance of the
reflected light
3. A visual response to light consisting of the three
dimensions of hue, value, and saturation
Glossary of Prosthodontic Terms – 8

Two systems have been extensively
used:
› The visually descriptive Munsell colour
order system
› The more quantitative CIELAB colour
system

 This system has been a popular method
of visually describing colour. The three
attributes of colour in this system are
called Hue, Chroma, and Value.
 To facilitate communication with the
technician, it is essential that the clinician
be thoroughly familiar with these terms
and their definitions.

Often referred to as the basic colour,
hue is the quality of sensation according to
which an observer is aware of the varying
wavelengths of radiant energy.
The dimension of colour dictated by the
wavelength of the stimulus that is used to
distinguish one family of colour from
another—as red, green, blue, etc.
The attribute of colour by means of
which a colour is perceived to be red,
yellow, green, blue, purple, etc. White,
black, and grays possess no hue.
Glossary of Prosthodontic Terms - 8

 The hue of an object can be Red,
Orange, Yellow, Green, Blue, Indigo or
Violet , and is determined by the
wavelength of the reflected and/or
transmitted light observed.
Kenneth Aschheim, Barry Dale. Esthetic Dentistry, a clinical approach to techniques and materials.

The place of the wavelength in the
visible light range of the spectrum
determines the hue of the colour. The
shorter the wavelength, the closer the
hue is to the violet portion of the
spectrum; the longer the wavelength,
the closer it is to the red portion.
Stephen F. Rosensteil, Martin F. Land, Junheo Fujimoto. Contemporary Fixed Prosthodontics,
fourth edition. www.indiandentalacademy.com

In younger permanent dentition,
hue tends to remain similar throughout
the mouth. With ageing, variations in
hue often occur because of intrinsic
and extrinsic staining from restorative
materials, foods, beverages, smoking,
and other influences.

The purity of a colour, or its departure
from white or gray
The intensity of a distinctive hue;
saturation of a hue
Chroma describes the strength or
saturation of the hue (colour)

 Chroma is the intensity of hue. The term
saturation and chroma are used
interchangeably in the dental
terminologies; both refer to the strength of a
given hue or concentration of pigment.
 A simple way of visualising differences in
chroma is to imagine a bucket of water.
When a drop of ink is added, a solution of
low chroma results, adding second drop of
ink increases the chroma, and so on, until a
solution is obtained that is almost all ink and
consequently of high chroma.

 In Munsell colour
system, the
intensity of chroma
of a particular Hue
is more intense on
the outer rim than
near the hub of
the wheel.
 In general chroma
of teeth increases
with age.
fourth edition.
Kenneth Aschheim, Barry Dale. Esthetic Dentistry, a clinical approach to techniques and materials.www.indiandentalacademy.com

The quality by which a light colour is
distinguished from a dark colour, the
dimension of a colour that denotes
relative blackness or whiteness (grayness,
brightness). Value is the only dimension
of colour that may exist alone.

 The brightness of any object is a direct
consequence of the amount of light energy
the object reflects and/or transmits.
 It is possible for objects of different hues to
reflect the same number of photons and
thus have the same brightness or value. A
common example is the difficulty
experienced in trying to tell a green object
from a blue object in a black and white
photograph. The two objects reflect the
same amount of light energy and therefore
appear similar in the picture.

 A restoration that has too high a value may
be easily detected by an observer and is a
common esthetic problem in metal-
ceramic restorations.
 A light tooth has a high value, a dark tooth
has a low value. It is not the quantity of the
colour gray, but rather the quality of the
brightness on a gray scale. That is, the
shade of colour(hue plus chroma) either
seems light and bright or dark and dim. It is
helpful to regard value in this way because
the use of value in restorative dentistry does
not involve adding gray but rather
manipulating colours to increase or
decrease amounts of grayness.
fourth edition.

Hues, as used in
dentistry, have a
relationship to one
another that can be
demonstrated on a
colour wheel. The
relationships of primary,
secondary, and
complementary hues
are graphically
depicted by the colour
wheel.

The Primary Hues- red, yellow, and
blue - form the basis of dental colour
system, in dentistry the metal oxide
pigments used in colouring porcelains
are limited in forming certain reds;
therefore pink is substituted.
The primary hues and their
relationships to one another form the
basic structure of the colour wheel.

The mixture of any two primary hues
forms a secondary hue. When red and
blue are mixed they create violet, blue
and yellow create green, and yellow and
red create orange. Altering the chroma of
the primary hues in a mixture changes the
hue of the secondary hue produced.
Primary and secondary hues can be
organised on the colour wheel with
secondary hues positioned between
primary hues.

Colours directly opposite
each other on the colour wheel
are termed complementary
hues. A pecularity of this system
is that a primary hue is always
opposite a secondary hue and
vice versa. When a primary hue
is mixed with a complementary
secondary hue, the effect is to
cancel out both the colours and
produce gray.
This is the most important relationship in
dental colour manipulation.

When a portion of a crown is too yellow,
lightly washing with violet(the
complementary hue of yellow) produces an
area that is no longer yellow. The yellow
colour is cancelled out and the area will
have an increase in the grayness(a lower
value). This is especially useful if the body
colour of a crown has been brought too far
incisally and more of an incisal colour is
desired towards the cervical area.
If the cervical area is too yellow and a
brown colour is desired, washing the area
with violet cancels the yellow. This is
followed by application of the desired
colour, in this case brown.

Complementary hues also exhibit the
useful phenomenon of intensification.
When complementary hues are placed
next to one another, they intensify one
another and appear to have a higher
chroma. A light orange line on the
incisal edge intensifies the blue nature
of an incisal colour.

 After 5 seconds of staring at a tooth or
shade guide, the eye accomodates and
becomes biased. If a person stares at a
particular colour for longer than 5
seconds and then stares away at a white
surface or closes his/her eyes, the image
appears, but in the complementary hue.
 This phenomenon is known as Hue
Sensitivity, this adversely affects shade
selection.

 An opaque material does not permit light to
pass through. It reflects all the light that is shined
on it.
 A porcelain fused to metal restoration must
have a layer of opaque porcelain applied to
the metal substructure to prevent colour of the
metal from appearing through the translucent
body and incisal porcelains. Improper tooth
reduction results in two unacceptable results:
 An ideally contoured restoration with minimal porcelain
thickness and too much opaque porcelain, resulting in a chalky
appearance.
 A bulky, poorly contoured restoration with ideal porcelain
thickness.
 Tooth preparation must be sufficient to allow
enough room for an adequate bulk of body
and incisal porcelains.

Translucent materials allow some light
to pass through them. Only some of the
light is adsorbed, translucency provides
realism to an artificial dental restoration.

In restorative dentistry, depth is a
spatial concept of colour blending
combining the concepts of opacity
and translucency. In natural dentition,
light passes through the translucent
enamel and is reflected out from the
depths of the relatively opaque dentin.

 White porcelain colourants used in
colour modification are opaque. Gray
porcelain colourants are a mixture of
white and black. A tooth restoration with
a white opaque colourant on the
surface appears artificial because it
lacks the quality of depth that would be
seen if the opaque layer were placed
beneath a translucent layer of porcelain.
 Similarly, a bright restoration(high value)
in need of graying(a decrease in value)
would appear falsely opaque if it were
simply painted gray.

 Adding a complementary hue,
however, both decreases the value and
adds to the translucency.
 If characterisation needs to be added
to porcelain to represent white
hypoplastic spots or gray amalgam
stains, white or gray colourants can be
used, but with the knowledge that
translucency will be reduced in these
areas.

 Depth may be problematic if translucent
composite resins are used to restore class
III or IV cavities that extend completely
from facial to lingual surfaces. The
restoration may appear gray or over
translucent. However, if a more opaque
composite resin is placed on the lingual
portion of the restoration and then
overlaid with a translucent resin a natural
illusion of depth results.

 The CIELAB colour system is used almost
exclusively for colour research in dentistry
around the world. It was introduced in
1976 and recommended by the
International Commision on Illumination.
 The strength of this system, unlike that of
Munsell system, is its ability for clinical
interpretation, as equal distances across
the CIELAB colour space(colour
differences or ∆E) represents
approximately uniform steps in human
colour perception, improving the
interpretation of colour measurements.

 This means that the magnitude of
perceptible and/or acceptable colour
difference can be defined between, for
example, a porcelain crown and the
adjacent natural dentition.
 The CIELAB colour order system defines
colour coordinates: L*, a* and, b*.
 L* is similar to the Munsell system’s Value
and represents the lightness, brightness, or
black/white character of colour. It
describes the achromatic character of
colour.
 The coordinates a* and b* describe the
chromatic characteristics of colour.

The chromatic, or non
black/white, characteristics
of a colour are represented
in Munsell’s colour system by
Hue and Chroma and in the
CIELAB system by a* and b*.
In each system, these two
coordinates define the
location of colour on a
plane of given lightness. In
the Munsell’s colour system,
the colour is identified by
one polar coordinate(Hue)
and one linear or Cartesian
coordinate(Chroma); in
CIELAB system, both
coordinates(a* and b*) are
Cartesian.

L* is the lightness variable
proportional to Value in the Munsell
system. It describes the achromatic
character of the colour.

The a* and b* coordinates describe
the chromatic characteristics of the
colour. Although they do not correspond
directly to Munsell’s Hue and Chroma,
they can be converted to numerical
parameters.

The a* coordinate corresponds to the
red-purple/blue-green axis in the Munsell
colour space. A positive a* relates to a
predominantly red-purple colour,
whereas a negative that is more blue-
green.
Similarly, the b* coordinate
corresponds to the yellow/purple-blue
axis.

The two major parts of the model are
its chromatic adaptation transform,
CIECAT02, and its equations for
calculating mathematical correlates for
the six technically-defined dimensions of
colour appearance: brightness
(luminance), lightness, colorfulness,
chroma, saturation, and hue.

CIECAM02 takes for its input the
tristimulus values of the stimulus, the
tristimulus values of an adapting white
point, adapting background, and
surround luminance information, and
whether or not observers are discounting
the illuminant (colour constancy is in
effect). The model can be used to
predict these appearance attributes or
with forward and reverse
implementations for distinct viewing
conditions, to compute corresponding
colours.

 It refers to the process, where the colour of
adjacent teeth is replicated in metal-
ceramic or all-ceramic restorations.
 The colour replication process for fixed
restorations consists of the shade-matching
phase followed by shade-duplication
phase. Shade matching can be
accomplished through either the more
common visual shade matching ot the
increasingly popular instrumental analysis.

 The shade duplication takes place in the
dental laboratory, in which either the use
of corresponding porcelain is selected in
the shade duplication phase or the use
of more sophisticated porcelain mixtures
is used to fabricate the restoration.
 If visually perceptible differences are
visible between the final restoration and
the originally matched restoration, it is
possible for the clinician to apply surface
characterisation porcelains to the
restoration to adjust any colour
discrepancy.

This phase occurs in the dentist’s
office, in which the information on the
colour and translucency of adjacent
teeth to be matched is recorded
through either visual shade matching
or instrumental colour analysis.

 Visual assessment of the shade and
translucency is the method most frequently
applied in dentistry.
 Studies have shown that this often-used
method is difficult to apply with accuracy
and often yields results that are unreliable
and inconsistent.
 Fortunately lifelike and successful
restorations do not have to be exact
duplicates of the colour and translucency
of natural adjacent dentition. It should
however blend with the teeth as a result of
distribution of ceramic material in the
restoration.

 Not only is the apparent colour of an
object influenced by its physical
properties, the nature of light to which
the object is exposed and the subjective
assessment of the observer; the
variability of two of the three factors, can
cause the same object to look different.
 Understanding of the three factors i.e.,
lighting, subjectivity of the human eye
and the object can improve the
accuracy and reliability of the shade
matching procedure.

 Light is necessary for colour to exist. An
object that is perceived as a certain colour
adsorbs all light waves corresponding to
other colours and reflects only the waves of
the objects colour.
 E.g., an object that adsorbs blue and green
light and reflects red appears red, the
quality and quantity of light source and the
environment in which the teeth or shade
guides are being visualised are important.

 Although daylight was
initially thought to be the
ideal light source for
colour matching, its use
is not recommended
any more, in view of the
inconstant colour
characteristics.
 The colour of daylight
can vary from red-
orange at sunset to blue
when the sky is clear.
The relative intensity of
daylight also fluctuates
during the day with
cloud cover.

An ideal light source for shade
matching is one that is diffuse and
comfortable for the eyes, allowing
observers to assess the colours
accurately and comfortably.

 Scientifically, light is described as visible
electromagnetic energy whose wavelength
is measured in nanometers(nm), or billionths
of a millimeter.
 The eye is sensitive only to the visible part of
the electromagnetic spectrum, a narrow
band with wavelengths from 380 to 750 nm.
At the shorter wavelengths lie ultraviolet, X,
and Gamma rays; at the longer
wavelengths are infrared radiation,
microwaves, and television and radio
transmission waves.

 Pure white light consists of relatively
equal quantities of electromagnetic
energy over the visible range. When it is
passed through a prism it splits into its
component colours because longer
wavelengths are bent less than shorter
ones.

 A light source of the appropriate
quality should be used during visual
shade matching. The appropriate
colour temperature with appropriate
spectral energy distribution and colour
rendering index(CRI) must be
considered when selecting a light
source.

 A light source with a colour temperature
close to 5500°K (D55) that is spectrally
balanced throughout the visible
spectrum is ideal for colour matching.
 Colour temperature is related to the
colour of a standard black body when
heated and is reported in degrees
Kelvin(°K).
 Accordingly, 1000°K is red, 2000°K is
yellow, 5555°K is white, 8000°K is pale
blue.

 D 65 is very commonly used in dental
shade matching as the standard lighting
for visual shade matching. A light source
with CRI greater than 90 is
recommended for shade matching.

Unfortunately, the most common light sources
in dental operatories are incandescent and
fluorescent, neither of which is ideal for shade
matching. An ordinary incandescent light bulb
emits relatively higher concentrations of yellow
light waves than of blue and blue-green, while
fluorescent fixtures emit relatively higher
concentrations of blue waves.

 Colour corrected fluorescent lighting is
recommended because it approaches
the necessary type of balance. Some of
the recommended commercial colour-
corrected ambient lighting, ideal for
shade matching are:
› CRS light
› Full spectrum, Supreme
› Lumichrome 1XX, 1XZ
› Demetron Shade Light
› Light-A-Lux
› Super Daylight

 Appropriate intensity of the ambient
lighting in the dental operatory provides
the dentist with visual comfort,
particularly in terms of contrast. It is
recommended that the light intensity for
the dental operatory be between 18
and 28 Lux, and 28 Lux for the dental
laboratory. The intensity of the dental
operatory lighting has not been found to
be crucial for colour matching when the
intensity ranged from 1.5 to 28 Lux.

 If ambient lighting in the dental operatory is
not ideal in terms of quality and quantity for
visual shade matching, the use of auxiliary
light source for shade matching is
recommended.
 The auxiliary light source for shade
matching should be intense enough to
overcome the influence of ambient light.
 It has been recommended that the ratio of
shade matching to ambient light should not
exceed 3:1; too much intensity does not
allow discrimination of small colour
differences.

 The ambient and direct lighting used for
shade matching scatters and reflects
from surfaces before reaching the
structure that it illuminates.
 The colours in the operatory, clothing of
the dentist and dental assistants, the
patient’s clothing, and the dental drape
may influence the perceived colour of
the patient’s teeth and shade guide.

 To maintain necessary lighting quality for
shade matching, the chroma of the
environment should be carefully controlled.
 It is recommended that the walls of the
operatory, staff clothing, patient drape,
and shade matching environment have a
Chroma of 4 Munsell units or less, which are
pastel or ideal neutral gray tones.
 Further the ceiling must have a Munsell
value of 9. All other major reflectors must
have a Munsell value of at least 7 and
Chroma not more than 4. Table tops may
have a chroma of upto 6 but Munsell value
of 7 or greater.

 Light from an object enters the eye
and acts on the receptors in the
retina(rods and cones). Impulses from
these are passed to the optical
center of the brain, where
interpretation is made.
 Shade matching is therefore
subjective: different individuals have
different interpretations of the same
stimulus.

 Under low lighting conditions, only the rods
are used(scotopic vision). These receptors
allow an interpretation of the brightness(but
not the colour)of the objects to be made.
The rods are most sensitive to blue-green
objects.
 Colour vision depends upon the cones,
which are active under higher lighting
conditions(phototopic vision).
 The change from phototopic to scotopic
vision is called as dark adaptation. And this
takes about 40 minutes.

The area with the
most cones is the
center of the retina,
which is free of rods.
The rods begin to
predominate towards
the periphery. This
means that the
central field of vision
is more colour
perceptive.

Although the exact mechanism of
colour vision is not known, there are
types of cones-sensitive to red, green,
and blue light-that forms an image in
much the same way as the additive
effects of pixels in a television picture.

Colour vision decreases rapidly as a
person stares at an object. The original
colour appears to become less and less
saturated until it appears almost gray.

 The brain can be
tricked in how it
perceives colour. A
classic example of
such a trick is the
Benham disk.
 When this black and
white disk is illuminated
and rotated at an
appropriate speed, it
appears to be highly
coloured.

 Colour is also influenced by surrounding
colours, particularly complementary
ones.
 For example, if blue and yellow are
placed side by side, their chroma may
appear to be increased. The colour of
teeth also look different if the patient is
wearing brightly coloured clothing.

 It is a phenomenon that can cause two
colour samples to appear as the same
hue under a light source, but as
unmatched hues under a different light
source.
 There is more than one way to produce
a colour. It can either be pure, or a
mixture of two other colours(e.g. pure
green versus a mixture of yellow and
blue)

 Pure green reflects light in green band, but the
green mixture reflects light in blue and yellow
bands simultaneously.
 If both colours are exposed to a light with a full
colour spectrum they will appear similar. If,
however, they are exposed to a light source
that does not contain light in the blue band,
the two colours will appear dissimilar. True
green will still appear green, but the mixture will
appear yellow because without a source of
light in the blue band the blue component of
the mixture is not visible to the eye.
 A spectral curve is a measure of the
wavelength of light reflected from a surface. It
reveals the actual component colours
reflected from an object.

 Metamerism complicates the colour
matching of restorations. A shade button
may match under incandescent lighting
from the dental operatory lamp but not
under fluorescent lighting in the patients
workplace.
 A colour selection that works well under a
variety of lights is preferred to a match that
is exact under one source of light but
completely wrong to others. Usually three
sources of light are available in the dental
operatory:
 Outside daylight through a window
 Incandescent lighting from the dental operatory
lamp
 Cool white fluorescent lighting from overhead
fixtures.

 Colour-corrected fluorescent lamps
more closely approximate natural
daylight and some practitioners prefer
them as the standard in dental
operatories.
 If the entire office is illuminated by
colour-corrected fluorescent lamp, one
room should have cool white fluorescent
lighting for comparative shade
matching. The colour match that holds
up the best in these three lights is the
best choice.

 Fluorescent materials, such as tooth
enamel, re-emit radiant energy at a
lower frequency than it is adsorbed.
 For example, UV radiation is reemitted as
visible light.
 A mismatch is said to be caused if the
restoration has a different fluorescence
from the natural tooth, but this is hardly
significant, clinically.

 Natural teeth particularly at their incisal
edges, exhibit a light scatter effect that
creates the appearance of bluish-white
colours as the teeth are seen at different
angles.
 This is similar to the bluish-white
background seen in opal gemstones –
hence the name.
 An attempt to match this effect in the
restoration is made.

 Defects in colour vision affects about 8%
of male population and less of the
female population
 They maybe of different types:
 Achromatism – complete lack of hue sensitivity
 Dichromatism – sensitivity to only two primary
hues- usually either red or green is not
perceived
 Anomalous trichromatism – (sensitivity to all
three hues with deficiency or abnormality of
one of the primary pigments in the retinal
cones)

 The most convenient
method for selecting a
shade is commercially
available porcelain
shade guides.
 Vita Lumin vacuum,
Ivoclar Chromascop and
Vitapan 3D-Master
shade guides are a few
examples.
 Each shade tab has a
opaque backing colour,
neck colour, body
colour, and incisal
colour.

 Shade matching consists of picking the
shade tab that looks the most natural
and reproducing this colour in a
laboratory with materials and
techniques recommended by the
manufacturer.
 The procedure is easier if specimens of
the same hue are grouped together in
the shade guide.

 The A1, A2, A3, A3.5 and A4 are
similar in hue, as are the B, C
and D shades.
 The recommended technique
to choose shades is, to first
choose the nearest hue and
then selecting the appropriate
match of chroma and value.
 If the chroma or intensity is low,
accurately determining a given
hue may be difficult. Therefore,
the region with the highest
chroma should be used for
initial hue selections.

 Once the hue is selected, the best
chroma match is chosen.
 For example, if B is the hue determined
to be the best match for colour variety,
there are four available gradation of
that hue: B1, B2, B3 and B4.

 Several comparisons are usually
necessary for determining which sample
best represents the hue and its
corresponding chroma(saturation) level.
 Between comparisons, glancing at a
gray object rests the operators’s eyes
and helps avoid retinal cone fatigue.

 Finally, value is determined with second
commercial guide whose samples are
arranged in order of increasing lightness.
 By holding the second guide close to the
patient the operator should be able to
determine if the value is within the shade
guide’s range. Attention is then focused
on the range of shade that best
represents the value of tooth and how
that range relates to the tab matching
for hue and saturation.

 An observer is able to assess the value most
effectively by observing from a distance,
standing slightly away from the chair, and
squinting the eyes. By squinting the observer
can reduce the amount of light that
reaches the retina. Stimulation of the cones
is reduced, and a greater sensitivity to
achromatic conditions may result.
 While squinting the observer concentrates
on which disappears from sight first - the
tooth or the shade tab. The one that fades
first has the lower value.

 Once the proper value selection is done,
it is exception rather than the rule for this
to coincide with the determinations for
hue and chroma. The operator must
then decide whether to change the
previously selected shade sample. If the
independent value determination is
lower than the value of the sample
selected for hue and chroma, a change
is usually necessary, because increasing
the value of an object by adding
surface stain is not possible.

 If the value determination is higher than
the hue determination, the operator
should decide whether this difference
can be bridged through internal or
surface characterisations of the
restoration.

 The shade samples here are
grouped in six lightness levels,
each of which has chroma
and hue variations in evenly
spaced steps. The shade
guide is spaced in steps (∆E)
of four CIELAB units in the
lightness dimension and two
CIELAB units in the hue and
chroma dimensions, the
difference between lightness
and colour steps seems a
logical approach to reducing
the number of shade samples
needed in the guide because
of the way the CIELAB units
are visually perceived.

 It seems to match the colour difference
formula of the Colour Mangement
Committee (CMC) of Society of Dyers
and Colourists, Because the guide is
evenly spaced, intermediate shades can
be predictably formulated by combining
porcelain powders.
 The manufacturers recommend
selecting the lightness first, then chroma
and finally the hue.

Determine the lightness
level (value)
 Hold shade guide to
patient’s mouth at
arms length
 Start with darkest
group moving right to
left
 Select Value group 1,
2, 3, 4, or 5
VITA Shade Guide Cataloguewww.indiandentalacademy.com

Select the chroma
 From your selected Value group remove
the middle tab (M) and spread the samples
out like a fan
 Select one of the three shade samples to
determine Chroma

Determine the hue
 Check whether the natural tooth is more
yellowish or more reddish than the shade
sample selected.

Final shade!

With the VITA Linearguide you can
determine the correct tooth shade
swiftly and accurately. The modern
design and systematic structure of the
VITA Linearguide enable the suitable
3D-MASTER shade to be found quickly.
The VITA Linearguide 3D-MASTER
contains the same 29 shade samples as
the VITA Toothguide 3D-MASTER. It
offers precise shade-taking in VITA
SYSTEM 3D-MASTER according to the
conventional procedure.

 Remove the VITA Valueguide 3D-MASTER
from the opened Linearguide.

 Make a first selection using the VITA
Valueguide.
 This way you determine the correct level
of lightness from 0 to 5.

 Now make a definitive selection within
the determined level of lightness from
step 1 using the corresponding VITA
Chroma/Hueguide.

The correct shade match!

 Most commercially available cover a
range more limited than the colours
found in natural teeth, and the steps in
the guide are greater than can be
perceived visually.
 Some porcelain systems are available
with extended-range shade guides.
 The use of two or more shade guides is a
practical way to extend the range of
commercial guides.

 When using a translucent all-ceramic
system for a crown or veneer,
communicating the shade of the
prepared dentin to the dental laboratory
is helpful. Some systems provide specially
coloured die materials that match the
dentin shade guide and enable the
technician to judge restoration’s
esthetics.

 Unfortunately, certain teeth may be
impossible to match to commercial
shade samples and also the
reproduction of these shades maybe
difficult.
 The extensive use of surface
characterisations has severe drawbacks.
As the stains increase surface reflection
and prevent light from being transmitted
through porcelain.

 This problem can be minimised by
extending the concept of a
commercial shade guide.
 An almost infinite number of samples
can be made by using different
combinations of porcelain powders in
varying different combinations in
varying distributions.

 This is a practical approach to accurate
shade matching and is recommended
even when a fairly good match is
available from the commercial shade
sample.
 The tooth is divided into three regions:
cervical, middle and incisal. Each region
is matched independently, either to the
corresponding area of a commercial
shade sample or to a single-colour
porcelain tab.

third edition. www.indiandentalacademy.com

 As only a single colour is matched,
intermediate shades can usually be
estimated rather easily and duplicated
by mixing porcelain powders.
 The junctions between these areas are
normally distinct and can be
communicated to the laboratory in a
diagrammatic form.

 The shade distribution and thickness
of the enamel porcelain are
particularly important. Individual
characteristics are marked on such
a sketch and will allow the ceramist
to mimic details like hairline fractures,
hypocalcification, and proximal
discolorations.

1. Shade matching should be made under
balanced lighting and in an appropriate
shade-matching environment with gray or
pastel colour walls and cabinets.
2. Anything on the patient that influences the
shade matching, including brightly
coloured clothing, should be draped, and
lipstick should be removed.
3. The teeth to be matched should be clean,
if necessary, stains should be removed by
prophylaxis.
4. Shade matching should be made at the
beginning of the patients visit, tooth colour
increases in value when the teeth is dry,
particularly if a rubber dam has been used.

5. Cheek retractors should be used to provide
an unhindered intraoral shade-matching
area.
fourth edition.
6. Choices of shade tab should be
expanded by using several shade
guides or mentally noting that the
shade of the tooth could be
between two shade tabs. The
technician should be asked to mix
the porcelain in equal quantities to
obtain a shade in between.
7. The patient should be viewed at eye level so
that the most colour sensitive part of the retina
is used. A viewing working distance of
approximately 10 inches(25cm) should be
adopted.

8. If the tooth and shade tab have different
surface characteristics, wetting the surface
of both helps remove the differences.
9. Shade matching should be made quickly,
i.e. in less than 5 seconds, with the shade
tab placed directly next to the tooth being
matched. This ensures that the
background of the tooth and the shade
sample are the same, which is essential for
accurate matching. The dentist should be
aware of eye fatigue, particularly of a very
bright fibreoptic illumination has been
used.

10. The dentist should rest his or her eyes
between viewings by focussing on a
neutral gray surface immediately before
shade matching, because this balances
all the colour sensors of the retina.
Resting eyes on a blue card was once
advised, but it is not recommended
because it results in blue fatigue.
11. To select the appropriate hue, the
canine tooth is recommended for
comparison because it has the highest
chroma of the dominant hue.

12. The dentist can select an appropriate
value by squinting.
13. The number of shade tabs should be
reduced an separated to approximately
three as quickly as possible. Then one or
two of the shade tab that matches the
best should be reslected.
14. Shade matching should be confirmed at
one or two visits and, if possible, confirmed
with an auxiliary staff member. It is also
recommended that shade selection be
confirmed under several different lightings.

15. If an exact match cannot be selected, a
shade tab with the lower chroma and
highest value should be selected, because
extrinsic characterisation can be used to
increase chroma and reduce the value.
16. The dentist should map the polychromatic
nature of the tooth being matched - its
special characteristics (e.g., cracks,
hypocalcifications, and translucency of
the incisal enamel of the tooth) - with one
of the following:
 A shade distribution chart
 A digital camera or 35 mm slide film with the closest
shade tab besides the tooth
 Staining of the closest matching shade tab

 Colour matching for dental restorations is
usually done by visual shade matching. In
industry, electronic colour measuring
instruments, such as spectrophotometers,
spectroradiometers, and colorimeters are
used.
 Spectrophotometers and spectroradiometers,
measure the light reflectance at wavelength
intervals over the visible spectrum.
Spectrophotometers differ from
spectroradiometers primarily in that they have
a stable light source and usually have an
aperture between the detector and sample.

 Colorimeters provide direct colour
coordinates specifications without
mathematical manipulation. This is
accomplished by sampling light reflected
from an object through three different
colour filters that simulate the response of
the colour receptors in the eye.
 Colour measuring instruments with an
aperture between the translucent object
and the illumination and sensor have been
shown to exhibit ‘edge loss’ when carrying
out measurements. Edge loss is a
phenomenon that occurs when light is
scattered through a transparent material
that originally would be seen by the eye but
is simply not measured by the instrument.

 This happens when the light is scattered in
the translucent object away from the
aperture and does not return back through
the aperture to the sensor and has been
shown to be wavelength dependent.
 Thus, colour measuring instruments
measuring translucent objects with an
aperture assign incorrect colour coordinates.
The phenomenon must be avoided if
accurate colour measurements of
translucent objects, like tooth and porcelain
are to be obtained, which is done by using a
combination of an external light source that
does not cause shadowing and a
spectroradiometer.

 These devices are generally one of the
three types:
› Colorimeters
› Spectrophotometers
› Digital Colour Analysers with various
measuring abilities.

 Various clinical colour measuring devices
are available.
› ShadeEye NCC (Colorimeter)
› Easy Shade (Spectrophotometer)
› ShadeScan (Digital Colour
Imaging/Colorimeter)
› ShadeVision (Digital Colour
Imaging/Colorimeter)
› SpectroShade (Digital Colour
Imaging/Spectrophotometer)
› ClearMatch (Software - to be used with a
digital camera)

 Errors associated with the duplication of the
selected shade with dental porcelain are
well documented.
 These errors are related to the underlying
metal used, the batch of porcelain powder
used, the brand of porcelain, and the
number of times glazing was performed.
 Visually detectable differences between the
colour of shade tab and the fired porcelain
is common, surface characterisations of
these errors may be used for corrections.

An understanding of the science of
colour and colour perception is cruicial
for the success of the restoration.
Although limitations in materials and
techniques may make a perfect colour
match impossible, a harmonious
restoration can almost always be
achieved.
Shade matching must always be
approached in a methodical manner.
This enables the practitioner to make the
best choice and communicate it
accurately to the laboratory.

Newly developed shade systems and
instruments may help the practitioner to
achieve a reliable restoration match.

1. Stephen F. Rosensteil, Martin F. Land,
Junhei Fujimoto. Contemporary Fixed
Prosthodontics, Fourth Edition.
2. Herbert T. Shillingburg, Jr., Sumiya Hobo,
Lowell D. Whitsett, Richard Jacobi, Susan E.
Brackett. Fundamentals of Fixed
Prosthodontics.
3. Ratnadeep Patil. Esthetic dentistry: An
artist's science.
4. Kenneth Aschheim, Barry Dale. Esthetic
Dentistry, a clinical approach to
techniques and materials.

5. Rafi Romano. The Art of the Smile:
Integrating Prosthodontics,
Orthodontics, Periodontics, Dental
Technology, and Plastic Surgery in
Esthetic Dental Treatment.
6. VITA Catalogue for Shade guide.

For more details please visit

Next seminar on
Fit and Insertion in Complete Denture
Prostheses
By Dr. Ashwin Pangi
on 24th January 2009

Shade selection/ orthodontics training courses

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