The use of a standardized gray reference card in dental

THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

VOLUME 11 • NUMBER 2 • SUMMER 2016

CLINICAL RESEARCH

The use of a standardized

gray reference card in dental

photography to correct the effects of

ve commonly used diffusers on the

color of 40 extracted human teeth

Sascha Hein, MDT

Private Dental Laboratory

Michael Zangl, MDT

Private Dental Laboratory

HEIN/ZANGL

CLINICAL RESEARCH

Correspondence to: Sascha Hein, MDT

Dentaltechnik Christ & Hein GmbH, Karl-Benz-Str. 25, 86825 Bad Wörishofen, Germany.

Tel.: 0049 8247 5320 Fax.: 0049 8247 31965; E-mail: [email protected]

THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

VOLUME 11 • NUMBER 2 • SUMMER 2016

HEIN/ZANGL

Abstract

Objective: The aim of this in vitro study

was to investigate the color changes of

human teeth caused by five different dif

fuser materials commonly used in dental

photography, as well as software influ

ence, and to confirm whether the use

of a standardized gray reference card

is effective in correcting these color

changes during digital postproduction.

Materials and method: Forty extracted

human teeth were obtained from a spe

cialized oral surgery practice in Cham,

Germany. Five commonly used diffuser

materials were chosen to be investi

gated, which included: polyethylene

(PET), White Frost photographic paper,

LumiQuest polyamide (nylon) mater

ial, 80 gsm white printing paper, and

3M linear polarizing filter sheet used for

cross polarization. A digital single-lens

reflex camera (Canon EOS5DMKII) was

used, together with a twin flash suitable

for macrophotography (Canon MT-24EX

Macro Twin Lite). Images were tethered

into Adobe Lightroom CC using the

RAW format. A standardized gray refer

ence card (WhiBal, Michael Tapes De-

sign) was used for exposure calibration

and white balancing. Classic Color Me

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ter software (Ricci Adams, version 1.6

(122)) was used to obtain CIE L*a*b*

values of the specimens before and af

ter white balancing and exposure cor-

rection.

Results: All diffusers caused visually

perceivable color changes on the ex

tracted teeth: White Frost (∆E* 1.24;

sd 0.47), 80 gsm printing paper

(∆E* 2.94; sd 0.35), LumiQuest polyam

ide (∆E* 3.68; sd 0.54), PET (∆E* 6.55;

sd 0.41), and 3M linear polarizing fil

ter sheet (∆E* 7.58; sd 1.00). The use

of a standardized gray reference card

(WhiBal) could correct these values be

low the visually perceivable threshold:

White Frost (∆E* 0.58; sd 0.36), 80 gsm

printing paper (∆E* 0.93; sd 0.54), Lu

miQuest polyamide (∆E* 0.66; sd 0.58),

PET (∆E* 0.59; sd 0.33), and 3M linear

polarizing filter sheet (∆E* 0.53; sd 0.42).

Signiﬁcance: The use of a standard

ized gray reference card with specified

CIEL*a*b* values should be considered

when diffusers are used in dental pho

tography in order to reveal the color of

preoperative situations (ie, shade docu

mentation) and document postoperative

results accurately.

(Int J Esthet Dent 2016;11:XXX–XXX)

THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

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CLINICAL RESEARCH

wavelengths will pass through. Due to

absorption, only specific wavelengths

that are characteristic of the material will

be transmitted. Hence, all the power that

is transmitted is concentrated in a few

narrow wavelength regions,

causing

large color distortions, since they affect

both the Correlated Color Temperature

(CCT) and the Color Rendering Index

(CRI) of the emitted light, making it diffi

cult to judge shade differences between

a shade tab or dental restoration and the

surrounding natural dentition on a digi

tal image. Preliminary relative irradiance

measurements of five commonly used

diffuser materials which were included

in this study, using a radiospectrometer

(Sekonic C-700, Sekonic), in conjunc

tion with a commonly used electronic

flash (Canon MT-24EX Macro Twin Lite),

revealed that different diffuser mater

ials did indeed influence CCT and CRI,

but only slightly. However, the visually

perceivable effects appeared notice

able in the digital images, suggesting

that software interpretation might play

a significant role (Fig 1). The use of a

standardized gray reference card prom

ises to overcome this limitation through a

remapping process of the original RAW

image to a defined standard. However,

natural teeth are heavy light scatter

ers, and irradiation with an intermittent

spectral power distribution may affect

their color within the threshold of visual

perception. The aim of this study was

to determine the effects that five com

monly used diffuser materials have on

tooth color, to identify their origin, and

to determine if the use of a gray refer

ence card is effective in correcting these

changes.

Introduction

The use of dental photography plays an

increasingly important role in everyday

dental practice as an effective tool for

communication between the dental sur

gery and the dental laboratory. Modern

digital single-lens reflex (DSLR) camer

as are in common use to document im-

portant restorative aspects such as the

preoperative situation, the tooth shade,

the final result, and long-term perfor

mance.

Photographic documentation

for purely medical purposes requires lit

tle more than basic equipment, such as

a DSLR camera paired either with a ring

or twin flash.

In the field of esthetic den-

tistry, however, elaborate assemblies

are often used to depict the restorative

process and especially the final result in

a rather “emotional” way, with the use of

various bouncers and diffusers and ad

justable brackets.

On the other hand,

cross polarized photography is a useful

method to reveal intrinsic shade varia

tions of natural teeth for the purpose of

shade analysis.

This is achieved with

the help of a linear polarizing filter sheet

that is placed over the electronic flash

in an orientation which is perpendicular

to that of another linear polarizing filter

simultaneously placed over the lens, re

sulting in the exclusion of diffuse light

and specular reflection from the labial

surface of natural teeth and dental res

torations alike.

Clinical experience has shown that

in vivo photographs of natural dentition

routinely show significant color altera

tions of teeth and soft tissue when cer-

tain types of diffusers are used.

When

a diffuser is placed in front of an illu

minant (ie, an electronic flash), not all

THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

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HEIN/ZANGL

Materials and method

Camera set-up

A digital single-lens reflex camera (Can-

on EOS 5D MKII) was used, together

with a twin flash suitable for macro pho

tography (Canon MT-24EX Macro Twin

Lite) (Figs 2 and 3). Images were teth

ered into Adobe Lightroom CC using

the RAW format and a USB 2.0 cable.

The screen (Cinema Display, Apple)

was calibrated using a spectrophotom

eter (ColorMunki, Pantone). The working

distance between the front of the lens

and the labial surface of one randomly

selected test specimen was varied to

achieve life-size magnification (1:1) at a

constant distance of 130 mm, as would

be the case in a clinical situation, and

Fig 1 Relative irradiance measurements reveal small influences on the Color Rendering Index (CRI)

and Correlated Color Temperature (CCT) caused by five diffusers when placed in front of an electronic

flash. Note that a variance in the rendering of the images occurs due to software interpretation of the DSLR

camera.

Canon MT-24EX Macro Twin Lite

6400 K (CRI Ra 100)

Linear polarizer

Printing paper

(80 gsm)

LumiQuest SoftBox White Frost Polyethylene PET

CRI Ra 97.2 CRI Ra 96.0 CRI Ra 97.6 CRI Ra 97.6CRI Ra 92.4

5864 K 5775 K 6108 K 5407 K5971 K

380 780

380 780 380 780 380 780 380 780 380 780

CLINICAL RESEARCH

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hence this value was chosen as the

standard distance for all measurements.

Using the camera’s manual mode, ex

posure time and aperture were set to a

constant value of 125/sec and f32. The

twin flash normally operates with four

AA Mignon batteries (Energizer Ultimate

Lithium, +AA 1.5V, 3000mAh). However,

preliminary tests showed noticeable var

iations in flash intensity after a few meas-

urement cycles due to battery depletion

and increased recycle time. In order to

overcome these limitations, a compact

battery pack which normally holds eight

additional AA Mignon batteries (Canon

CP-E4) was modified to be attached to

a 12 V, 1500 mAh direct current trans

former (Yumatron, Model NT6), ensuring

steady flash intensity and short recycling

times (< 5 s). The camera was attached

to a microcomputer (Stack Shot, Cogn

isys) that was programmed to trigger the

camera shutter nine times in a row, with

a precisely timed interval of 15 s.

Diffuser materials

Five commonly used diffuser materials

were chosen for the study: polyethyl

ene (PET), White Frost photographic

paper (ProTech Lighting), Mini SoftBox

polyamide (nylon) material (LumiQuest),

80gsm white printing paper, and 3M lin

ear polarizing filter sheet used for cross

polarization. The materials were cut into

squares and attached to a set of cus

Figs 2 and 3 The experimental setup consisted

of a DSLR camera paired with a twin flash com-

monly used for dental photography. In order to mini-

mize specular reflection from the labial surface of

the teeth, both electronic flash guns were arranged

in two azimuthal illumination angles correspond-

ing to 0 degrees/45 degrees geometry using two

aluminum rails and two custom 3D-printed variable

sled assemblies.

Fig 4 Five commonly used diffuser materials were

chosen for the study. They included polyethylene

(PET), White Frost photographic paper, LumiQuest

polyamide (nylon) material, 80gsm white printing

paper, and 3M linear polarizing filter sheet used for

cross polarization. Each frame had an open window

of 80mmx55mm.

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tom-made frame holders with an open

window of 80 mmx55 mm (Fig 4).

Specimen assembly

In order to minimize specular reflection

from the labial surface of the teeth, both

electronic flash guns were arranged in

two azimuthal illumination angles cor

responding to 45 degrees/0 degrees

geometry using two aluminum rails and

two custom 3D-printed variable sled

assemblies. The specimen holder con

sisted of a square block made of mela-

mine, which was designed to hold one

extracted tooth in its middle which could

be exchanged and repositioned pre

cisely using a round ABB grid pattern

(LEGO). An adjustable slot allowed the

attachment of two square pieces of the

gray reference card in the same vertical

plane as the tooth specimen. The dis

tance from each of the diffusers to the

labial surface of a randomly chosen test

specimen was 150 mm.

Specimen preparation

Forty-four extracted, unrestored teeth

were delivered to the dental labora

tory already stored in a 0.9% solution of

thymol. The teeth had been previously

cleaned and pumiced before visual in

spection for suitability was carried out.

Four specimens were discarded be

cause they showed severe signs of

damage from the extraction surgery. The

remaining 40 teeth (Table 1) were mildly

sandblasted with 50 µm aluminum ox

ide to remove the surface gloss from the

enamel in order to avoid specular reflec

tion that could obstruct color measure-

ments. The tips of the roots were cut

off before they were attached to round

ABB grid patterns (LEGO) using super

glue gel and accelerator spray, while

fixing them in a perpendicular position

using the sample holder for guidance.

The specimens were numbered and re

turned to a jar that contained 0.9% thy-

mol solution to preserve their color.

White balance reference card

A standardized white balance refer-

ence card (WhiBal, Michael Tapes De-

sign) was used. This particular product

was chosen because of its even reflec

tance and its defined color coordinates

(CIE L*75; a*0; b*0). The manufactur

er claims a chromaticity accuracy of

∆C*< 0.71 (a*±0.5; b*±0.5) (Fig 5). In

a previous investigation, triple measure

ments of 14 individual new WhiBal cards

were carried out with a spectrophotom

eter (ColorMunki) to confirm this claim

(∆C*0.29). One WhiBal card was ran

domly chosen and cut into two squares

to be used on either side of the tooth dur

ing the entire measurement sequence.

Table 1 Forty extracted human teeth were obtained from a specialized oral surgery practice in Cham,

Germany, and deemed suitable for inclusion in the study

Tooth 14 16 17 18 22 23 24 26 27 28 31 33 36 37 38 41 44 46 47

Quantity 4 1 4 2 1 1 1 1 1 5 2 2 4 3 2 1 1 3 1

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THE INTERNATIONAL JOURNAL OF ESTHETIC DENTISTRY

VOLUME 11 • NUMBER 2 • SUMMER 2016

Custom white balance was carried out

using the camera’s menu function and

one WhiBal card, which was positioned

in the same horizontal plane and dis

tance as the tooth specimen.

Measurement sequence

Each measurement sequence com-

menced with a hydrated tooth in place

and two squares of WhiBal cards to the

left and right of it, with two empty frame

holders in front of each electronic flash.

The first four photographs were taken

in this way, followed by one photograph

each using five different diffuser ma

terials: PET, White Frost, LumiQuest,

80 gsm printing paper, and 3M linear

polarizing sheet. In order to obtain im

ages with increased tonality and dy-

namic range, as well as reduced noise,

the concept of “exposing to the right”

(ETTR) was used, with red–green–blue

(RGB) values distributed predominantly

to the right of the exposure histogram.

The camera ISO was set to a value of

100, and the flash intensity to a value of

½ (half), except for the 80 gsm printing

paper and linear polarizing sheet, due

to the noticeable attenuation of luminous

flux. For adequate comparability with the

standard, an adjustment of the ISO to a

value of 200, as well as an adjustment of

the flash intensity to a value of 1/1 (full)

was required with this particular group.

Each complete measurement cycle took

a total of 135 s.

Digital image development

and color measurements

The first image was immediately dis-

carded since it only served to empty

the flash capacitor. The following three

Fig 5 The color accuracy of 14 new gray reference cards (WhiBal) was measured and confirmed to be

within the margin of error claimed by the manufacturer (∆C*<0.71; (a*±0.5; b*0.5)).

a b c

75.00

75.32

75.63

75.95

76.26

76.58

76.89

77.21

77.53

77.84

76.53

a* b*

-0.50

-0.42

-0.34

-0.26

-0.18

-0.11

-0.03

0.05

0.13

0.21

0.29

0.37

0.45

-0.14

-0.50

-0.42

-0.34

-0.26

-0.18

-0.11

-0.03

0.05

0.13

0.21

0.29

0.37

0.45

-0.25

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images taken with no diffuser were ex-

posure balanced by moving the cursor

over the gray area of the WhiBal card.

Due to the camera’s custom white bal

ance, it was merely necessary to adjust

the exposure of the image until the lu

minosity value of the gray card in the

photograph matched L*75. The values

for chromaticity (a*+b*) were within the

threshold of ±0.5 each time, as claimed

by the manufacturer. The same proced

ure was carried out with the five photo-

graphs taken with each diffuser material.

Color Meter Classic software (Ricci Ad

ams, version 1.6 (122)) was used to lo-

cate an area in the middle of each tooth.

The measurement window was adjusted

to the maximum size possible within the

boundary of the tooth in order to meas

ure CIEL*a*b* color coordinates. Once

this position was locked, values for each

tooth were copied and pasted into a

spreadsheet (Numbers (version 3.5),

Apple) (Fig 6). In order to determine the

standard error caused by subtle varia

tions in flash intensity, the first three sets

of color coordinates from the gray card

where averaged and compared with the

ideal value of L*75; a*0; b*0. If ∆E* was

< 1.0, the measurement sequence was

included in the study; if the value was

∆E* > 1.0, the tooth was to be measured

again (which was never the case). Once

the color coordinates for the five differ

ent diffuser groups were recorded, white

balancing was carried out by choosing

the eyedropper tool in Adobe Lightroom

CC and clicking on a randomly chosen

gray area in close proximity to the tooth.

In most cases it was then necessary to

adjust the exposure values again to ob

tain L*75; a*0; b*0, before the color coor-

dinates of the tooth could be recorded.

Results

∆E* was calculated as described in the

CIE prescriptions:

∆E*

= √(L*

- L*

)

+ (a*

- a*

)

+ (b*

- b*

)

All diffuser materials caused visually per-

ceivable color changes on the extracted

teeth. The values for the different diffus

er materials before and after white bal-

ance correction can be seen in Figure 7:

White Frost (∆E* 1.24; sd 0.47), 80 gsm

printing paper (∆E* 2.94; sd 0.35), Lu

miQuest polyamide (∆E* 3.68; sd 0.54),

PET (∆E* 6.55; sd 0.41), and 3M linear

polarizing filter sheet (∆E* 7.58; sd 1.00).

The use of a standardized gray refer

ence card (WhiBal) could correct these

values below the visually perceivable

threshold (Fig 8): White Frost (∆E* 0.58;

sd 0.36), 80 gsm printing paper

Fig 6 Color measurements were carried out using

Classic Color Meter software in the middle of each

tooth. The measurement window was adjusted to

the maximum size possible within the boundary of

the tooth to measure CIEL*a*b* color coordinates.

Once this position was locked, values for each tooth

were recorded in the exact same position.

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(∆E* 0.93; sd 0.54), LumiQuest polyam-

ide (∆E* 0.66; sd 0.58), PET (∆E* 0.59;

sd 0.33), and 3M linear polarizing filter

Fig 7 Color changes of 40 extracted teeth caused

by five diffuser materials commonly used in den-

tal photography. White Frost (∆E* 1.24; sd 0.47),

80gsm printing paper (∆E* 2.94; sd 0.35), Lumi-

Quest polyamide (∆E*3.68; sd0.54), PET (∆E*6.55;

sd0.41), and linear polarizing filter sheet (∆E*7.58;

sd1.00).

∆E

0.00

2.25

Trend 1

4.50

6.75

9.00

2 4 6 8

y = x

= 1

∆E

1.24

∆E

2.94

∆E

3.68

∆E

6.55

∆E

7.58

Fig 8 The use of a standardized gray reference

card (WhiBal) could correct the color changes be-

low the visually perceivable threshold: White Frost

(∆E*0.58; sd0.36), 80gsm printing paper (∆E*0.93;

sd0.54), LumiQuest polyamide (∆E*0.66; sd0.58),

PET (∆E*0.59; sd0.33), and linear polarizing filter

sheet (∆E*0.53; sd0.42).

∆E

0.00

0.40

0.80

1.20

1.60

0 1

y = x + 1.986E-16

= 1

∆E

0.53

∆E

0.66

∆E

0.93

Fig 9 The average exposure compensation that

was required during digital postproduction was:

White Frost (EV-0.20; sd 0.106), 80gsm printing

paper (EV-0.38; sd0.114), LumiQuest polyamide

(EV-0.55; sd0.108), PET (EV-0.55; sd0.197), and

linear polarizing filter sheet (EV-0.70; sd0.116).

-0.90

-0.68

Average exposure adjustment

-0.45

-0.23

0.00

-0.7 -0.525 -0.35 -0.175

y = x

= 1

-0.20

-0.38

-0.55

-0.70

sheet (∆E* 0.53; sd 0.42). The aver-

age exposure compensation that was

required during digital postproduction

is illustrated in Figure 9: White Frost

(EV -0.20; sd 0.106), 80 gsm print

ing paper (EV -0.38; sd 0.114), Lumi-

Quest polyamide (EV -0.55; sd 0.108),

PET (EV -0.55; sd 0.197), and 3M lin

ear polarizing filter sheet (EV -0.70;

sd 0.116).

Discussion

During the era of film photography, so

called “gray cards” (ie, Kodak) were

used in conjunction with the camera’s

light metering system (TTL) to determine

the correct exposure for objects illumi

nated by continuous light sources like

the sun. With the arrival of digital photog

raphy, it became necessary to use white

balance reference cards, which in their

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general appearance were similar to the

older gray cards but darker, in order to

correct the color cast of digital images,

either by defining a custom white bal

ance value using the camera’s menu, or

during postproduction using software.

The protocol that has been put forward

here is an adapted, simplified version

of the one suggested by Meng et al,

which combines the correction of white

balance with exposure correction to a

defined standard.

The use of a white balance refer

ence card was indeed effective in

compensating the changes in tooth

color caused by different diffuser ma

terials (∆E*

min

0.53-∆E*

max

0.93) and

software interpretation. Every diffuser

caused characteristic tooth chroma

Figs 10a and b Changes of tooth color caused by different diffuser materials (a) before, and (b) after

white balancing, using a standardized gray reference card.

Fig 11 Average change

of chromaticity caused by

different diffuser materials.

∆a*

0.00

2.00

4.00

6.00

8.00

White Frost

1.28

∆b*

Printing paper

(80 gsm)

LumiQuest

SoftBox

Polyethylene

PET

Linear

polarizer

0.51

0.72

0.30

2.96

2.57

6.20

2.86

7.81

1.33

Fig 12 The average tooth color found in this study

showed little deviation.

0.00

20.00

Average tooth color

40.00

60.00

80.00

0 20 40 60

y = x+8.205E-15

= 1

L* 74.78

a* 3.78

b* 16.53

a b

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ticity changes, which can be seen in

Figures 10 and 11. The ranking of ∆E*

values after white balancing correlated

well with the ranking of CRI values for

each diffuser (Fig

12), suggesting that

software interpretation plays the most

significant role in the visually perceiv

able alteration of tooth color before

white balancing.

The average tooth color found in this

study showed little deviation (Table 2).

This result corresponds generally well

with those of other studies,

but in par-

ticular with one in vivo study by Gozalo-

Diaz et al, which utilized a similar experi

mental setup and equipment, and which

found a similar average tooth color value

to that found in this study (∆C* 2.99).

This supports the suggestions by ear

lier authors

14-18

that digital cameras can

be used confidently for quantification of

tooth colors.

The closest match to conventional

shade guide systems was the shade

1C (∆E* 1.90) from the Ivoclar PE shade

guide system, which is made of hard

acrylic, followed by Vita 3M shade 2R2.5

(∆E* 2.14), and Ivoclar PE shade 1A

(∆E* 2.31) (Table 3).

A basic protocol for practical use in

the dental surgery and dental laboratory

is provided in Figures 13 to 15.

Table 2 The ranking of ∆E* values after white balancing correlated well with the ranking of CRI values for

each diffuser, suggesting that software interpretation plays the most significant role in the visually perceiv-

able alteration of tooth color before white balancing

Diffuser material CRI ∆E*

Linear polarizer

97.2 0.53

White Frost

97.6 0.58

PET

97.6 0.59

LumiQuest SoftBox

96.0 0.66

Printing paper (80 gsm)

92.4 0.93

Table 3 The closest match to conventional shade guide systems

L* a* b* Shade ∆E*

72.960 4.336 16.527 1C

1.90

73.928 3.865 14.571 2R2.5

2.14

73.094 3.381 15.003 1A

2.31

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Fig 13 White balancing procedure: After importing the RAW file into Adobe LightroomCC, the color

picker tool is selected to click on a randomly selected area of the white balance reference card ideally

located in the center of the image. This will neutralize chromaticity values a* and b* towards 0 (±0.5).

white balance

Fig 14 Exposure balancing procedure: The color picker tool is held steadily over the central area of the

white balance reference card while the exposure value is adjusted simultaneously until the L* value is as

close as possible to the known L* value of the gray reference card (ie, L*75 WhiBal).

exposure balance

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Fig 15 The adjustments during white balancing and exposure balancing can be copied and pasted to

achieve synchronicity among images which were obtained with the same type of diffusor.

copy and paste

Conclusion

Within the limitations of this study, the

use of a white balance reference card

with known color coordinates can be

recommended when diffusers are used

for dental photography in daily practice

to record color accurate images, espe

cially for shade communication and for

documentation of clinical results.

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References

1. Bengel W. Mastering Digital

Dental Photography. Quin-

tessence, 2006:2–6.

2. Ahmad I. Digital dental

photography. Part 4: choos-

ing a camera. Br Dent J

2009;206:575–581.

3. Ahmad I. Digital dental pho-

tography. Part 5: lighting. Br

Dent J 2009;207:13–18.

4. Bazos P, Magne P. Bio-

Emulation: biomimetically

emulating nature utilizing

a histoanatomic approach;

visual synthesis. Int J Esthet

Dent 2014;9:330–352.

5. Gordon P, Wander P. Spe-

cialised equipment for dental

photography. Br Dent J

1987;162:346–359.

6. Ahmad I. Digital dental

photography. Part 8: intra-

oral set-ups. Br Dent J

2009;207:151–157.

7. Berns RS. Billmeyer and

Salzman’s Principles of Color

Theory, ed 3. New York: John

Wiley and Sons, 2000:4.

8. Martinec E. “Noise, Dynamic

Range, and Bit Depth in

Digital SLRs”, 2008. http://

theory.uchicago.edu/~ejm/

pix/20d/tests/noise/noise-p3.

html. Accessed 17 Septem-

ber 2015.

9. Bengel W. Mastering Digital

Dental Photography. Quin-

tessence, 2006:148–149.

10. Meng J, Kontogiorgos E,

Newby M. An Alternative

Method of Shade Selection

for Indirect Dental Res-

torations: A Case Report.

http://www.mtmengs.net/

images/joe/Articles/Joe%20

Meng-%20Poster%20-Ameri-

can%20Adademy%20of%20

Fixed%20Prosthodontics%20

2008.pdf. Accessed 10 May

2015.

11. Snow SR. Assessing and

Achieving Accuracy in Digi-

tal Dental Photography. CDA

Journal 2009;37.

12. Bosch JJ, Coops JC. Tooth

color and reflectance as

related to light scattering and

enamel hardness. J Dent

Res 1995;74:374–380.

13. Gozalo-Diaz D, Johnston

WM, Wee AG. Estimating

the color of maxillary cen-

tral incisors based on age

and gender. J Prosthet Dent

2008;100:93–98.

14. Cal E, Sonugelen M, Guneri

P, Kesercioglu A, Kose

T. Application of a digital

technique in evaluating the

reliability of shade guides. J

Oral Rehabil 2004;31:483–

491.

15. Jarad FD, Russel MD, Moss

BW. The use of digital imag-

ing for colour matching and

communication in restora-

tive dentistry. Br Dent J

2005;199:43–49.

16. Luo W, Westland S, Ellwood

R, Petty I. Uncertainties in

tooth colour measurement

using digital camera. In:

Proceedings of the 30th

International Congress of

Imaging Science, Rochester,

2006:582–584.

17. Reno EA, Lapujade P, Poore

CM, Crisanti MM, Miller JM,

Anastasia MK. Reproducibil-

ity of a digital imaging meth-

od for measuring tooth color.

J Dent Res 2002;81(special

issue A):2726.

18. Smith RN, Collins LZ, Naeeni

M, et al. The in vitro and in

vivo validation of mobile

non-contact camera-based

digital imaging system for

tooth colour measurement. J

Dent 2008;36(suppl 1):S15–

S20.