ASTM E2545-07

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: E2545 – 07
Standard Test Method for
Objective Measurement of Gingival Color Using Digital Still
Cameras
This standard is issued under the fixed designation E2545; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The color of gingiva is an important parameter used to ascertain certain medical and esthetic
information. RGB color values for gingiva are derived from the native signals generated by a digital
stillcamera,DSC,bybroadbandmeasurementofthereflectanceofgingiva.Thistestmethod,E 2545,
specifies the procedure used for the color measurement of gingival color at 45° relative to the sample
plane containing the gingiva under a nearly equal energy illuminating at 45° and viewing at 0°. This
method is appropriate for evaluating the color of facial gingiva.
1. Scope 1.4 The apparatus, measurement procedure, and data analy-
sis technique are generic, so that a specific apparatus, measure-
1.1 This test method covers the procedure, instrumental
ment procedure, or data analysis technique may not be ex-
requirements, standardization procedures, material standards,
cluded.
measurement procedures, and parameters necessary to make
1.5 The values stated in SI units are to be regarded as the
precise measurements of gingival color. In particular it is
standard. The values given in parentheses are for information
meant to measure the color of gingiva in human subjects.
only.
1.2 Digital images are used to evaluate gingival color on the
1.6 This standard does not purport to address all of the
facial labial or buccal surfaces of the gingiva. The marginal
safety concerns, if any, associated with its use. It is the
gingival tissue adjacent to natural teeth may be of particular
responsibility of the user of this standard to establish appro-
interest for analysis.All other non-relevant parts; such as teeth,
priate safety and health practices and determine the applica-
tongue, spaces, dental restorations or prostheses, etc., must be
bility of regulatory limitations prior to use.
separated from the measurement and the analysis.All localized
discoloration; such as stains, inclusions, pigmentations, etc.,
2. Referenced Documents
may be separated from the measurement and the analysis.
2.1 ASTM Standards:
1.2.1 The broadband reflectance factors of gingiva and the
E179 Guide for Selection of Geometric Conditions for
surrounding tissue are measured. The colorimetric measure-
Measurement of Reflection andTransmission Properties of
ment is performed using an illuminator(s) that provides con-
Materials
trolled illumination on the gingiva using a digital still camera
E284 Terminology of Appearance
to capture the digital image.
E308 Practice for Computing the Colors of Objects by
1.3 Data acquired using this test method may be used to
Using the CIE System
assess personal gingival color for the purposes of identifying
E1345 Practice for Reducing the Effect of Variability of
overallhealthstatus,healthstatusatspecificsitesinthemouth,
Color Measurement by Use of Multiple Measurements
or to track changes in personal health status for individuals
E1767 Practice for Specifying the Geometries of Observa-
over time. Pooled data may be used to assess gingival color,
tion and Measurement to Characterize the Appearance of
health and disease among populations in epidemiological
Materials
surveys, evaluation of comparative product efficacy, or safety
2.2 ISO Publications:
and treatment response in clinical trials involving gingival
health or disease.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is under the jurisdiction of ASTM Committee E12 on Color contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and Appearance and is the direct responsibility of Subcommittee E12.06 on Image Standards volume information, refer to the standard’s Document Summary page on
Based Color Measurement. the ASTM website.
Current edition approved May 1, 2007. Published July 2007. DOI: 10.1520/ Available from International Imaging Industry Association (13A), 701
E2545-07. Westchester Avenue, Suite 317W, White Plains NY 10604, www.13a.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E2545 – 07
ISO 17321–1 Colour characterization of digital still cam- converting the RGB camera values to component CIELAB
eras (DSCs) — Part 1: Stimuli, metrology, and test values are also presented.
procedures
5. Significance and Use
ISO/IEC 1544–1:2000 – JPEG2000 Information technology
– JPEG 2000 image coding system – Part 1: Core coding 5.1 The color of gingiva or changes in gingival color can be
observed. The light reflected from the facial surfaces of the
system, commonly known as JPEG 2000 jp2 file format
2.3 ISCC Publications: gingiva can be used to calculate color coordinates. These data
reveal information about the efficacy of a product, treatment
Technical Report 2003–1 Guide to Material Standards and
Their Use in Color Measurement studied, or epidemiology of anti-gingivitis treatments. For
example, clinical studies of gingivitis treatment systems evalu-
2.4 Other Publications:
ate the efficacy of manufacturers’ products.
TIFF Tagged Image File Format
5.2 The change in color of the facial surface gingiva can be
3. Terminology used to determine and optimize the efficacy of anti-gingivitis
treatments.Forexample,thedatacanprovidetheanswertothe
3.1 Terms and definitions in Terminology E284 are appli-
question: “What product or system is the most efficacious in
cable to this test method.
the treatment of gingivitis?”
3.2 Definitions: Terms included in this section are peculiar
5.3 Chronic inflammatory disease of the gingiva and peri-
to this standard.
odontium results in destruction of gingival connective tissue,
3.2.1 angle of incidence, n—u and optional u , the polar
1 2
periodontal ligament, and alveolar bone. Clinically, inflamma-
angle between the central ray of the illuminator(s), I and I ,
1 2
tion is seen as redness, swelling, and bleeding observed upon
and the Z axis which is the optical axis of the camera.
probing.
3.2.1.1 Discussion—These are shown in Fig. A1.1.
5.4 This procedure is suitable for use in diagnosis and
3.2.2 bit depth, n—the number of digital bits used to store
monitoring, research and development, epidemiological or
information contained in each color channel of each pixel.
other surveys, marketing studies, comparative product analy-
3.2.2.1 Discussion—Thebitdepthdeterminesthemaximum
sis, and clinical trials.
number of colors that may be encoded by the system. For
5.5 Popular methods assess gingival inflammation via re-
example, a 24 bit system comprising 8 bits per channel can
6,7
8 8 8
peated clinical examination of the gingival tissues. These
encode 2 by 2 by 2 or about 17 million; colors far more than
methods typically quantify gingival color, which are used to
are distinguishable by the human observer.
assess gingival health or disease, at multiple intraoral sites on
3.2.3 facial surfaces, n—the surfaces of teeth and gingiva
the gingiva using a simple non-linear scoring system or index.
that are oriented outward toward the lips (labial) and cheeks
Assessment of gingival color is an important component of
(buccal), and facing away from the tongue or roof of the
health status for mild-to-severe gingival disease. These tech-
mouth.
niques are time-consuming, subjective, and often invasive, and
3.2.4 gingivitis, n—inflammation of the marginal gingiva in
for archival purposes, separate intraoral photographs must be
response to dental plaque accumulation on adjacent tooth
collected to document gingival color and appearance.Variation
surfaces.
between and among examiners may contribute to appreciable
3.2.5 in-vivo—adj, or adv, within a living body.
differences in measurement.
3.2.5.1 Discussion—Used to describe measurements made
in a living body.
6. Interferences
3.2.6 polarization, n—the process by which vibrations of
6.1 The interferences identified below may be eliminated
light are given a definite orientation; also the state produced by
andproblemsavoidedbycontrollingandregulatingeachfactor
that process.
within the constraints of the allowable experimental error. The
3.2.7 polarizing filter, n—a component that blocks one of
values and limits for these factors are typically determined
the two planes of vibration of an electromagnetic wave, thus
experimentally. If the standard laboratory conditions listed
producing linearly polarized light.
below change during the test or from test to test by an
appreciable amount, these conditions may cause interferences,
4. Summary of Test Method
andtheaccuracyandprecisionrequirementsofthistestmethod
4.1 Thistestmethoddescribestheproceduresforbroadband
may not be achieved. In some cases these effects may only be
reflectometry of gingival tissue. The standardization of the
observed during the performance of the test.
instrument used to measure the tissue is defined.The images of
6.1.1 Factors Affecting Test Results—The following envi-
artifact standards and samples are captured with a DSC. The
ronmental factors are known to affect the test results.
RGBvaluesoftheseimagesarereadandstored.Theresultsare
reported as RGB values and can be converted to other
colorimetric coordinates such as CIELAB. Procedures for Loe H., and Silness, J., “Prevalence and Severity,” Journal Peridontal Disease
in Pregnancy, I, Acta Odontologica Scand , 1963, 21:533-551.
Lobene,R.R.,Weatherford,T.,Ross,N.M.,Lamm,R.A.,andMenaker,L.,“A
modified gingival index for use in clinical trials,” Clinical Prevention Dentistry,
Available from ISSC, Inter-Society Color Council, 11491 Sunset Hills Rd., 1986, 8:3–6.
Reston, VA 20190, www.iscc.org. McClanahan, S. F., Bartizek, R. D., and Biesbrock, A. R., “Identification and
TIFF, Tagged Image File Format, Adobe Systems Incorporated, San Jose, CA, consequences of distinct Loe-Silness gingival index examiner styles for the clinical
http://www.adobe.com. assessment of gingivitis,” Journal of Periodontology, 2001, 72:383–92.
E2545 – 07
6.1.1.1 Extraneous Radiation—Light including near infra-
red from sources other than the illuminator(s) must be shielded
from the test apparatus.
6.1.1.2 Vibrations—Mechanical oscillations that cause
components of the apparatus to move relative to one and
another may cause errors in test results.
6.1.1.3 Thermal Changes—Temperature changes occurring
during a test or differences in temperature between testing
locations may affect the reflectance factor of the standardiza-
tion, calibration, and verification plaques, and the apparatus
spectral response function.
6.1.1.4 Power Input Fluctuations—Large changes in the
line frequency or supply voltage may cause the apparatus to
report erroneous results
6.1.2 Retractors—The surface finish of the retractors affects
the experimental test results. It has been determined that a
FIG. 1 Subject Positioned in Instrumentation
glossy finish on the surface of the retractors may introduce a
bias into the test results.
6.2 The system must allow for successful standardization. If
the system cannot be standardized, a series of checks must be
performed (lighting, camera, etc.) to identify the reason. The
component of the system in error will be adjusted or replaced
to bring the system back into calibration.
7. Apparatus
7.1 General—The components described in this section are
described generically. The intention is not to exclude any
component from being used, or to exclude any type of
instrument that may be available commercially. Between 4 and
6 different components or component assemblies are required
to accomplish the measurement.
7.2 Geometry—The geometry of the system is 45:0 as
FIG. 2 Chin Rest
described in Practice E1767. The DSC System Geometry
(Coordinate System) and Angular Convention are shown in
Fig. A1.1 included in Annex A1.
ratio, transmittance, and beam deviation are important param-
7.3 Components—A block diagram of these component
eters of the components and must be selected.
assembliesisshowndiagrammaticallyinFig.A1.2,includedin
7.3.4 Heat Rejection Filters—These filters remove undes-
Annex A1.
ired near infrared (IR) radiation including heat that adversely
7.3.1 Source Illumination Assembly—Contains the source
affects the subject, and provide spectral shaping of the spectral
of illumination and associated optics to produce irradiance, E,
power distribution of the source illumination
on the sample over a specified spot area, designated A. The
7.3.5 Selective Blue Filters—These filters condition the
source is broadband and continuous in nature.Adiagrammatic
spectral power distribution of the illumination so that the
representation of the components of a typical source illumina-
spectral power distribution is similar to Illuminant D50.
tion assembly Unit is shown in Fig. A1.3, included in Annex
7.3.6 Sample Plane Holder—The sample plane holder pro-
A1.
vides a secure mount so that it positions the subject’s incisors
7.3.2 Spectral Power Distribution—The light source should
normaltotheZaxis,andcenteredalongtheXandYaxes.This
be spatially uniform over the area of interest, and have a
mustbedonesothatthegingivaltissueispresentedtotheDSC
spectrum that approximates CIE Illuminant D50 over the
in a repeatable and reproducible manner. The sample mount
spectral range of the DSC, a choice that is customary and
must be kept unobtrusive so that it is “friendly” and not
achieves the uniformity of practice. Commonly used light
intimidating to the subjects. A chin rest is used to precisely
sources include incandescent lamps with filters to simulate a
position the subjects relative to the instrumentation (Fig. 1).
standard illuminant, flash xenon with filters, or white-LED
The subjects place their chin on a chin rest which is a
lamps to realize the approximate color temperature of 5000K.
quarter-cup shaped rig, as shown in Fig. 2.
7.3.3 Polarizer—The linear polarizer provides and controls
7.3.6.1 Lip retractors (Fig. 3) are used to expose the
the polarization state of the incident light.This polarizer on the
majority of the subject’s gingiva to the DSC system. Subjects
illuminators plus a cross polarizing filter on the lens system of
the DSC eliminates glare caused by reflection of the subject’s
gingiva tissue during imaging. Wavelength range, extinction Retractors with a matte finish have been found satisfactory for this purpose.
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