Shade matching a single maxillary central incisor

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Shade Matching a Single Maxillary Central Incisor
James F. Fondriest, DDS*
QDT 2005
1
ccurately reproducing the unique charac-
teristics of a single maxillary central in-
cisor so that the artificial replacement is
perceived as “natural” can be the biggest chal-
lenge in restorative dentistry. This challenge
comes at several levels. First, the practitioner
needs to have an understanding of what factors
go into achieving a good match as well as some
basic knowledge of the nomenclature of light sci-
ence in or
der to communicate what is seen. Sec
-
ond, the practitioner is responsible for creating a
protocol to accurately assess what is happening
when light hits the surface of the tooth to create
its appearance. There are ways to enhance what
we see visually or photographically in the mouth
by lessening metamerism, afterimages, and other
visual distortions.
[Au: is sentence ok as modi-
fied?] Third, the practitioner needs to develop
written, graphic, and photographic communica-
tion devices that are more comprehensive and
less confusing. For example, there is no common
dental standard for communicating the degree of
translucency, hypocalcification of enamel, or vary-
ing degrees of surface luster. If we had to describe
in gr
eat detail the teeth shown in Fig 1 without
photography, how many words would it take to
deliver a nonconfusing synopsis? And last, labora
-
tory staff needs to develop their skills along with
the practitioner partner because all of the levels of
communication conveyed to the lab must also be
recognized and understood in the photographs.
It is important to realize that matching the hue
and chr
oma is fifth or sixth in impor
tance on the
list of things to match when constructing a pros-
thetic r
eplacement.
1
A person would have to be
fairly close to detect subtle dif
ferences in hue; yet
disparities in sur
face morphology, value, and opac-
ity can be seen from 4 or 5 feet away or more. Dis-
parate tooth silhouettes or perimeter shapes of the
teeth can be seen from even 10 feet away. The
order of importance while matching a single maxil-
*Private practice, Lake Forest, IL.
Correspondence to: Dr James F. Fondriest, 560 Oakwood
Avenue, Suite 200, Lake Forest, IL 60045, USA.
E-mail: jimfondriest@cs.com
A

FONDRIEST
QDT 2005
2
lary central is (1) silhouette or perimeter shape, (2)
surface morphology and texture, (3) value, (4)
translucency or opacity, (5) chroma, and (6) hue.
SHAPE, MORPHOLOGY, AND TEXTURE
The appearance of teeth is mostly determined by
how light interacts with its curved and varied sur-
face. The perimeter shape and the morphology of
the buccal surface have the greatest affect on the
appearance of teeth because they determine how
the majority of light is reflected. An observer only
sees an object when light comes from that object.
Sur
faces that ar
e smooth and perpendicular to us
send more light back to us (Fig 2). Reflective sur-
faces of the tooth will not r
etur
n significant light
to our eyes if they ar
e not perpendicular to our
eyes, even if the tooth surfaces are highly pol-
ished. Figure 3 illustrates this concept with sand
that is uniform in color. The sand looks very differ-
ent depending on its contour and angle of illumi-
nation.
The textur
es of a maxillar
y central incisor can
be divided into three subcategories: vertical, hori-
zontal, and localized. V
er
tical textures tend to be
manifestations of the three developmental lobes.
Horizontal textures are initially created by the
placement of enamel layer upon layer. The end of
each layer leaves a line on the enamel sur
face
called
the striae of Retzius.
2
These striae run
roughly parallel to each other and are called
perichymata. As the years go by
, the surface of
the tooth wears and the striae eventually disap-
pear. Different sections of the tooth calcify with
different levels of mineralization and hardness. In
time these dissimilarly hardened areas can wear
unevenly, forming much larger and more widely
spaced horizontal undulations. The localized group
of surface textures is a catchall for characteriza-
tions such as “orange peel,” stippling, cracks,
craze lines, chips, developmental defects, etc.
Reflection from a smooth surface results in the
production of a clear, well-defined image. This is
called
specular reflection. A specular reflection re-
turns a high percentage of direct, nondiffused
light and, if strongly illuminated, will be brighter
and stand out. Most teeth have irregular surfaces
with convexities and concavities. The convexities
(Fig 4) tend to wear and become smooth with
specular reflective characteristics. Concavities
tend to collect light by reflecting inward and are
often unpolished, thus diffusing the light and re-
turning less light to the viewer’s eyes. The visual
impact of a tooth comes from the specular high-
lights that reflect off the heights of contour and
give the tooth its visual shape and perceived
length and width dimensions.
3
Smoothing the texture of the buccal surface
makes teeth appear lighter and brighter and
therefore gives them a significant determinate of
value. The more reflective the surface, the more
wavelengths r
etur
n to the obser
ver
’
s eyes, and the
additive combination of more wavelengths yields
whiter light (hue, chr
oma, value, and opacity all
change). If we wer
e to smooth out the wind-rip
-
pled sand in Fig 3, it would appear brighter.
Brighter objects appear closer to the viewer. This
is why a restoration that is too light appears to
“jump out at” the viewer. Lowering the value
makes objects appear farther away.
Silhouette and sur
face morphology ar
e best
documented with photography. Photographic
pr
otocols ar
e described later in this article. Value
is the next most important parameter of color
matching.
Fig 1 How easy would it be to describe these teeth in
written form?

Shade Matching a Single Maxillary Central Incisor
3
QDT 2005
VALUE
Value, or brightness, is the sum total of light that
returns from the target tooth (contralateral maxil-
lar
y central incisor) to the eyes. The brightness of
teeth is mainly determined by the saturation or in-
tensity (chroma) of hue and the surface reflectivity
as discussed above but is also appreciably af-
fected by the optical characteristics common to
translucent bodies. These optical characteristics,
in or
der of impor
tance, ar
e opacity, opalescence,
fluor
escence, and optical density.
Human teeth are characterized by varying de-
grees of opacity. Translucency and opacity can be
defined as the measurement of the gradient be-
tween transparent and opaque. Value is affected
by the opacity of the various layers of the tooth.
As the opacity incr
eases, mor
e light is scatter
ed
instead of being transilluminated. Reducing the
surface luster of a piece of clear window glass by
wet sanding or etching produces a frosty-white
look. As light hits the surface of the etched glass,
it scatters or bends irregularly. This scattering of
the light at the sur
face causes an incr
ease in opac
-
ity (Figs 5 and 6). The light does not travel
through and away from the surface but rather is
reflected. As the glass becomes less translucent,
the value incr
eases. The net ef
fect is that mor
e
light returns to the viewer as the luster diminishes.
Polishing the r
ough glaze of
f a por
celain
r
estoration is a subtle way to lower value by mak-
ing the porcelain clearer and more translucent.
5
Super-polished surfaces can appear bright be-
cause of the crisp specular reflection, but they
also have more translucency because the light is
not scattered or bent at the surface. It is important
to note that sur
face textur
e, and not luster
, deter
-
mines specular reflection. With the window glass
3
2
4
Fig 2 A high percentage of light that hits a surface at a
90-degr
ee angle will return to the viewer, while light
that hits a sur
face at an oblique angle will be deflected
away fr
om the viewer.
Fig 3 Appearance varies depending on surface contour
and the angle of illumination.
Fig 4 There is a double [Au: do you mean twice the
reflection and absorption, or that both occur?]
reflec-
tion and absorption of light in concavities, causing
diminution of light coming from these areas, while light
is reflected more in bulging and curved areas.

QDT 2005
4
FONDRIEST
example, although the surface has been rough-
ened, the glass remains flat and has low texture,
so it will remain a specular reflector.
Opalescence can be described as a phe-
nomenon where a material appears to be one
color when light is reflected from it and appears
to be another color when light is transmitted
through it.
6
A natural opal is an aqueous disilicate
that breaks transilluminated light down into its
component spectrum by refraction. Opals act like
prisms and refract (bend) different wavelengths to
varying degrees. The shorter wavelengths (blues
and purples)
[Au: colors correct as inserted?]
bend more and have a higher critical angle
needed to escape the optically dense enamel
than the longer wavelengths [Au: ok as in
-
serted?] (reds and yellows). The hydroxyapatite
cr
ystals of enamel also act as prisms. When illumi
-
nated, enamel will transilluminate the reds and
scatter the blues within its body. This is why
enamel not backed by red-yellow reflecting
dentin, such as at the incisal edge or interproxi-
mally, will appear bluish even though it is intrinsi-
cally colorless.
7–9
The opalescent ef
fects of enamel
brighten the tooth and give it optical depth and
vitality
.
10
The easiest way to evaluate enamel thick
-
ness is to look for the opalescent blue ar
eas. Doc-
umentation of the translucent enamel is best done
photographically since dentistry lacks the words
to describe levels of opacity.
Fluorescence by definition is the absorption of
light by a material and the spontaneous emission
of light with a longer wavelength.
11
Fluorescence
in a natural tooth primarily occurs in the dentin
because of the higher amount of organic material
present.
2,7,8,12
The more invisible ultraviolet (UV)
light the dentin absorbs, the more it fluoresces,
therefore increasing the value.
7
We live in a world
of UV light. UV light can have a dramatic effect on
the brightness of teeth and restorations. The den-
tal practitioner cannot measure fluorescence easily,
but the porcelains used in the restoration should
have fluorescent qualities or else the value will be
too low in sunlight or other high UV situations.
When light enters enamel, it gets bounced
around the enamel. If one side of a tooth is illu-
minated with a curing light, the entire crown is
lighted. Similar to a fiber
-optic cable
[Au: your
analogy implies that fiber-optic cables are
made of optically dense materials. Is this what
you mean?], enamel is an optically dense mate-
rial bordered by air and dentin, both of which
have significantly lower optical densities. Nor-
mally, increasing opacity or reflectivity increases
value. By increasing the optical density of dental
ceramics, the fiber
-optic pr
oper
ties of natural
enamel can be replicated, and the prosthetic
cr
own can be bright and translucent at the same
time. It is with the translucent enamel layer that
the ceramist achieves color depth and the illusion
of a vital natural tooth. Measurement of optical
density is difficult and not necessary, but porce-
lains that have higher optical densities tend to be
more lifelike.
Fig 5 A roughened surface diffuses light.
4
Fig 6 A smooth, polished surface produces a
well-defined image and can be more translucent.
4

CHROMA AND HUE
Every opaque object in your sight is receiving
light or is r
eceiving the three primary color ranges
of red, green, and blue-violet in some ratio. Some
of these objects reflect all of the light they receive
and others absorb it almost completely.
7
Most
“opaque” objects absorb part of the light and re-
flect the rest. The dominant wavelength(s) reflected
back to your eye is the perceived color of the ob-
ject. White objects reflect almost all visible light
rays. Black objects absorb most of the light so
nothing is reflected back to your eyes.
Hue is the quality that distinguishes one family
of colors from another. Hue is specified as the
dominant range of wavelengths in the visible
spectrum that yields the perceived color. Chroma
is the saturation, intensity, or strength of the hue.
SHADE ASSESSMENT SYSTEMS
Shade tabs from any vendor are helpful. Ideally prac-
titioners should have the same shade guide the lab-
oratory uses, but if not, the tab can be shared while
the restoration is being completed. [Au: do changes
express your intended meaning?] The Vita classic
shade guide (Vita Zahnfabrik, Bad Säckingen, Ger-
many), at this time, is used by about 90% of practi-
tioners. This guide unfor
tunately r
epresents a minor-
ity of the natural teeth and unnaturally brightened
teeth to be matched. It is hoped that a nonpropri-
etary, universal, full-spectrum guide will be available
in the not-too-distant future that the dental material
manufacturing industry will adopt. Better shade tab
systems that cover more of the hue and value spec-
trums, such as the Vitapan shade guide [Au: mfr lo-
cation?], ar
e cur
r
ently on the market; however
, V
ita-
pan is tied to a proprietary porcelain system.
The cur
r
ent mechanical shade-assessing systems
based on colorimeters, spectr
ophotometers, or
camera sensors (char
ge-coupled device or
CMOS
[Au: please spell out “CMOS.”]) will not rival
the results achieved when the practitioner/techni-
cian team utilize well-drawn shade maps and quality
multi-image photography.
13
MEASURING LOW-LIGHT VALUE
Value is best evaluated in low or subdued light.
When the V
ita classic shade guide is arranged by
order of value (as suggested by the manufacturer)
and evaluated in good light, the order might be
considered suspect. Some of the darker-appearing
tabs seem to be in the middle. If viewed in sub-
dued light (the amount of light present during an
ominous thunderstorm with dark clouds), the
order seems perfect. The discrepancy occurs be-
cause of color confusion. In more light the color-
perceiving cones in our eyes are stimulated and
the color in the tabs becomes more evident. The
colors confuse the observer’s ability to assign
value intensities. In lower light, the cones are not
stimulated and only the rods are activated. The
rods in our eyes are sensitive to lightness and
darkness, or grayscale. Rods, which are used in
night vision, are very sensitive even with small
amounts of light. The cones are activated only
with higher light levels. (Consider that, except for
colored lights, we do not see colors at night when
driving.) In summary, ambient light levels should
be low enough so that colors are not that obvious
and only the rods in your eyes are used to assess
the brightness of the target tooth. Some authors
have suggested squinting as a way to assess
value.
14,15
The practitioner should instruct the labo-
rator
y to confir
m in low light the overall value of
the final restoration.
Low-light value should be the first parameter
evaluated in the restorative procedure. By assess-
ing low-light value first, the pupils have not been
reduced by the glare of the bright dental unit
light.
16
Also, the tooth has not become dehydrated.
Dehydration increases opacity of the enamel. Light
no longer can go fr
om hydr
oxyapatite cr
ystal to
crystal. Intraoperative dehydration causes signifi-
cant changes in value, translucency
, chr
oma, and
hue. Less translucency causes mor
e reflection, so
the tooth is brighter
.
12
Chr
oma, being inversely re-
lated to value, is reduced, and the hue becomes
more the color of the light source, which is as-
sumed to be white. Once the low-light value is de-
termined, hue and chroma tabs can be selected.
QDT 2005
5
Shade Matching a Single Maxillary Central Incisor

SELECTING SHADE TABS
Create a neutral-colored environment. Comple-
mentar
y-color afterimages of any bright color will
occur in milliseconds. The ideal background when
assessing color is neutral gray.
17,18
Neutral gray has
no complementary color and is restful to the
cones. A neutral gray environment is more critical
with aged teeth that have a glossy surface that re-
flects the shade of any color placed in close prox-
imity (Aiba N, personal communication, 2001).
18–20
The color of the walls in the operatory and labora-
tory can alter color perception and should be sub-
dued. In a blue room more orange is seen than is
actually present because the complement of blue
is orange. A gray bib can be used to cover the pa-
tient’s clothes,
21
and lipstick should be removed or
covered. The amount of red tissue seen in the
background can be limited by cropping it out with
intraoral gray backgrounds (Pensler Shields,
#50009211, Kulzer
[Au: location?]. These dispos-
able cardboard backgrounds can be shaped easily
to match the arch form. If the background card is
positioned too far behind the teeth and out of
focal distance, the gray will darken to black, which
increases glare.
7, 22
The most important parameter of selecting hue
is the lighting condition. Because of the variability
of daylight, both the practitioner and lab techni-
cians should used window blinds along with a
color-corrected light that approaches 5,500 K (a
color rendering index of 93) and has the proper
luminosity. [Au: correct as edited, or is the CRI a
third criteria for the light?] Viewing teeth under
diffuse illumination will minimize the distortion of
reflected light. Reflection from the specular sur-
faces of a tooth reveals more of the color of the il-
luminating light than the color of the tooth.
23
The
average recommended luminosity for dental
shade matching is 150 foot-candles.
15,19,24–27
T
o
have light of this intensity in the operator
y at the
level of the dental chair
, 8 to 10 4-ft fluorescent
bulbs would be needed in a 10 x 10-ft room with
8-foot ceilings.
19,26
[PROD: mult sign] The diffusion
panels covering fluorescent bulbs are important
because they can screen out wavelengths. As they
age, the panels change what wavelengths they
absorb. The best diffusers, preferably the “egg-
crate” type, are those that do not filter out any
wavelengths of the spectr
um. Using 10 color-cor-
rected bulbs on the ceiling will yield more light in
the operatory than would be considered comfort-
able. Portable high-quality light units, such as the
Vident light,[Au: location?] are ideal.
First impressions are the best, because of the
effects of eye fatigue. To prevent hue accommo-
dation, practitioners should not stare at the teeth
for more than 5 seconds.
15
Miller has suggested
using a Vita classic shade guide arranged by hue
with the A and B hues at opposite ends and C
and D in the middle. C and D have hues in be-
tween A and B
28
on the linear rainbow (chroma
and value are manipulated to yield different
looks). When choosing the hue family, a clinician
can use the A4 and B4 or A2 and B2 tabs, which
facilitate the process of elimination by using tabs
with the greatest hue spreads.
15
The chroma is
very low for shades A1 and B1. It can be difficult
to distinguish the proper hue family using these
tabs. When choosing the hue with a shade tab,
the practitioner should look to the midbuccal area
of the tooth. Differences between the shade tab
and the natural colors of the tooth increase near
the root. Compared to the Vita classic shade
guide, natural teeth exhibit increased redness and
lower translucency at the cer
vical aspect.
20,29
If in
doubt about the hue family, the A family can be
chosen,
30
since perhaps as many as 80% of natural
teeth are a closer match to this hue family (Miller
L, personal communication, 2001). Most natural
teeth have more red than is in the B family. An-
other guideline for shade matching is to hold the
incisal edge of the shade tab to the incisal edges
of the teeth. This position ef
fectively isolates the
shade tabs from the teeth so they do not reflect
onto each other (Aiba N, personal communica
-
tion, 2001)
20
;
it also reduces afterimages.
Most humans experience eye dominance, and
one eye will preferentially perceive shade.
16
It is
wise to hold the shade guide on both sides of the
tooth at each vector (Aiba N, personal communi-
cation, 2001). In addition, difficulties can arise
QDT 2005
6
FONDRIEST

when the tooth being examined differs consider-
ably in size from the specimen on the shade
guide. A variation in color perception can occur
with the r
elatively larger area appearing brighter
and more vivid than the smaller area.
31
SHADE MAPPING
In dental ceramics, clinicians and technicians try to
imitate the appearance of the tooth as a sum of all
its visual dimensions. In addition to providing ex-
cellent photographic images for the technician, it
is extremely valuable to provide a written graphic
with an interpretation of these dimensions in the
drawing. If no shade tab matches what is seen,
then a tab can be customized by applying surface
stains. Caution must be used with this technique
because the lab is encouraged to duplicate this
surface staining, which will increase metamerism
in the final restoration.
32,33
All that is seen should be shade-mapped in full-
page, three-dimensional drawings or on printed
photographs of the target tooth and other proxi-
mal teeth. Several views (eg, 90-degree straight
buccal, 135-degree angle from the buccal-incisal
aspect, and straight incisal/occlusal) can be used.
The labial face of the crown is then divided into
zones. The low-light value from gingival to incisal
should be noted, and the base hues should be
mapped, along with the chroma stops in the vari-
ous areas
[Au: do changes reflect your intended
meaning?] of the buccal surface. A chroma stop is
an arbitrary measurement of hue saturation and is
designated by the number of the Vita classic
shade guide. Do not hesitate to alter these
chroma-stop designations. For example, it is ac-
ceptable to note an ar
ea to be A2.5 or A3.75
even though there are no tabs that have these
chr
oma intensities.
The sur
face anatomy must be described. The
pr
eoperative models will help in duplicating the
contours. Although the luster and texture can be
better determined photographically, the clinician
should describe it on the prescription form and in-
clude the age of the patient. Surface texture and
luster can be described as heavy, moderate, or
light, and different combinations of surface char-
acteristics can be given. Because these surface
featur
es determine the character of light reflection
and affect the amount of light that enters the
tooth, the surface morphology of a crown should
be designed to simulate the light transmission
and reflectance pattern of adjacent teeth.
4,5,29,34–38
When the practitioner is mapping the translu-
cency of the target tooth, he or she looks for the
opalescent blue areas. They are more visible with
the use of a black background, which limits the
reds reflecting from the back of the mouth and re-
adding
[Au: this term is awkward. “combin-
ing”?] to the blues to yield white light again.
39,40
When drawing proximal translucence, the clinician
should ask the patient to turn from right to left,
which allows a better analysis. This reevaluation at
different angles is called
vectoring.
16,36,41,42
The practitioner and technician should build a
collection of shade guides and tabs that can be
shared between the team. Some proprietary
guides have tabs that represent different levels of
enamel opacity, frost, occlusal staining, etc.
PHOTOGRAPHIC DOCUMENTATION
PROTOCOLS
Developing exper
t photographic skills is wor
th-
while because better images yield more informa-
tion. The practitioner is responsible for creating an
environment and protocol to assess what is hap-
pening when light hits the surface of the tooth to
create the appearance of the tooth. There are
ways to increase what is seen photographically in
the mouth,
40,43
and some fairly simple chore-
ographed images ser
ve to communicate the mor
e
important parameters for matching. Communicat-
ing with photography will always be better than
with written or verbal descriptions. Almost all
quality levels of images ar
e better than nothing.
That alone should encourage more photographic
documentation.
Shape, surface morphology, translucency,
chroma, and hue can all be documented well
QDT 2005
7
Shade Matching a Single Maxillary Central Incisor

QDT 2005
8
FONDRIEST
using three choreographed photographs: one
each for silhouette and surface morphology,
translucency, and hue and chroma.
Silhouette and Surface Morphology
When the lens and flash are positioned over the
surface of the tooth, the light will reflect off the
perpendicular surfaces back to the camera, as off
a mirror. All surfaces not perpendicular will reflect
the light away from the camera, highlighting the
texture variations (Fig 7).
The following guidelines will help to obtain a
photograph that best r
epr
esents the tooth silhou
-
ette and surface morphology:
•
Use a black backgr
ound. (This is preferred but
not mandatory.)
• Orient the camera lens perpendicular to the
surface being evaluated.
• Dry and clean the surface of the tooth.
• Vector for gingival, midbuccal, and incisal thirds.
[Au: what is meant by “vector”? to take a
perpendicular photo at each of these levels?]
• Use a dual-point or cir
cumferential flash to best
capture surface morphology. These types of
flash mechanism maximize the r
eflections.
Translucency
Camera flash reflections are very helpful when evalu-
ating textures. However, these reflections obscure the
view below the surface of the tooth. Flash reflections
should be minimized in the photograph when evalu-
ating translucency. The target tooth can be wetted
for evaluation of translucency, hue, and chroma to
limit the influence of surface morphology. Reflections
can be limited by angling the lens (more than 30 de-
grees) away from perpendicular to the target tooth
surface and taking the photograph from above or
below (Fig 8). More angulation may be necessary
with a ring flash since ring flashes tend to surround
the exposur
e field and yield mor
e r
eflections.
A few steps will enhance translucency in a
photograph:
• Clean the teeth.
• Use a black background.
• Close down the aperture to allow discernment
of layers and depth.
• Set the flash on manual (turn off through-the-
lens [TTL] flash) and slightly under
expose by in
-
crementally adjusting the F-stop, which allows
us to see into the tooth better by fur
ther r
educ-
ing the surface reflections.
•
Angle the lens at least 30 degrees from perpen-
dicular so reflections do not return to camera.
Fig 7 The silhouette and surface morphology are best
photographed at a right angle to the camera lens.
[Au:
tips in figs 7 to 9 have been set in the text and leg-
ends adapted.]
Fig 8 Translucency is enhanced when the camera is an-
gled 30 degrees off perpendicular.

Chroma and Hue
Visual distortions dramatically affect our ability to
render color.
7
The two main distortions in dental
circumstances are the spreading effect and the
negative afterimage. Simply stated, the spreading
effect occurs when two dissimilarly colored ob-
jects are placed next to each other. Because our
eyes do not stare fixedly at an object but rather
continually r
oam the visual field, the color of one
object is mixed with that of another object, and
within seconds the objects appear more alike. If
some distance is placed between the tooth and
the midbuccal part of the shade guide, a better
assessment can be made. Some clinicians advo-
cate grinding off the incisal edge of the Vita clas-
sic shade tabs, but the incisal edges of the tabs
do help provide that little visual separation, which
lessens the spr
eading ef
fect
7, 22,44
(Aiba N, personal
communication, 2001). Orient the shade tabs so
that the incisal edge of the tab co-appr
oximates
[Au: can “co-” be deleted without affecting
your meaning? or
, describe the term in other
words.]
the incisal edge of the tooth (Fig 9).
Contrast is caused by a difference between the
brightness or color of an object and its immediate
background. Object forms with high contrast are
easier to detect than objects with low contrast.
While some contrast is helpful to our visual sys-
tem, excessive contrast causes glare. An ex-
tremely bright object against a dark background
causes discomfort and can interfere with color
perception.
7,22
This interference is generically
called glar
e
. This glar
e r
educes our ability to per
-
ceive visual information. With dental photography,
the use of a black background increases impact,
but it will cause glar
e. An incr
ease in glare is coun-
terproductive when matching hue and chroma,
and it will mask shade mismatches.
Negative afterimages are caused by fatigue of
the cones in our eyes. Afterimages are often seen
in the form of complimentary colors. Background
r
eds in the mouth cr
eate the per
ception of mor
e
blue than is actually present. An achromatic back-
gr
ound is quite valuable in hue assessment. The
18% reflective gray card is the photographic in-
dustr
y standard achromatic background. A gray
card creates less glare and fewer afterimages.
QDT 2005
9
Shade Matching a Single Maxillary Central Incisor
Fig 9 Chroma and hue can be communicated when three shade tabs are
placed edge to edge with the reference tooth and a reflective gray card is
set in the background.

Chroma and hue can be effectively recorded by
following these recommendations:
• Clean the tooth surface. Saliva can be left on
the surface, but water tends to flatten the sur-
face and lessens reflections caused by surface
textures.
• Use an 18% reflective gray card background.
• Take the photographs at least 30 degrees from
perpendicular to the surface to prevent reflec-
tions that will obscure proper evaluation.
• Arrange three shade tabs incisal edge to incisal
edge. Tabs should be parallel and equidistant
to the teeth from the lens. The center tab is
considered an ideal match, while the other tabs
represent one chroma stop up or down.
• Create slight underexposure by using manual
flash settings rather than using TTL flash and
adjusting the compensation settings. This will
make chroma evaluation easier.
Bracketing in Manual Mode
Varying the film/sensor exposure can be accom-
plished several ways and is called
bracketing. One
type of bracketing is the incremental adjustment
of the lens aperture by fractions of an F-stop while
multiple exposures are being taken. When the
aperture, or lens opening, is closed down, less
light will reach the film or digital sensors. Bracket-
ing F-stops is beneficial in documentation pho-
tography because often dif
fer
ent things ar
e seen
at different settings. Closing down the F-stop will
decrease the influence of surface reflections but
not decr
ease the ability to see the opalescence. It
also increases the depth of field. Closing down
the F-stop will increase the ability to see the layers
within the tooth, which is helpful for determining
translucency, hue, and chroma.
45
The camera has
to be set to manual with a constant shutter speed
and flash. The TTL flash setting cannot be used
with this technique. All exposures can be sent to
the laboratory
, but the slightly underexposed im-
ages deliver more information.
SUMMARY
To produce a lifelike restoration, it is important for
the clinician and technician to develop their skills
at describing the features of a tooth. A sequential
protocol for selecting value and shade tabs, shade
mapping, and then photographing for shape and
surface morphology, translucency, and finally
chroma and hue has been described. This proto-
col allows the clinician to capture detailed and ac-
curate information about the appearance of the
tooth, which will aid the dental technician in creat-
ing a faithful reproduction. The steps described in
this article should be followed before any restora-
tive procedures are performed and even before
the dental unit light is turned on.
[Au: the sum-
mary has been adapted with portions from your
original abstract. ok? it has also been abbrevi-
ated to avoid excess repetition.]
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FONDRIEST

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QDT 2005
11
Shade Matching a Single Maxillary Central Incisor