ASTM E2670-09

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Designation:E2670 −09
StandardTest Method for
Objective Quantification of Dental Plaque Using Digital Still
Cameras
This standard is issued under the fixed designation E2670; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Dental plaque is a biofilm, which grows on teeth and surrounding tissue. In many cases, dental
plaque is the underlying cause of many oral diseases, that is, cavities and gum diseases. Thus,
controlling dental plaque through its removal and inhibition of re-growth is essential to maintaining
good oral health. Today, there are hundreds of products produced to control dental plaque. Examples
are; toothbrushes, toothpastes, floss, rinses, gums and routine dental cleanings. One universal design
objective maximizes plaque control through enhanced cleaning ability or chemistry which inhibits
plaque growth; that is, anti-bacterial agents. Often, the effectiveness of a product or procedure is
measured in a clinical trial with traditional methods of estimating plaque coverage. For example, the
modified Turesky index is often used. This index is an integer scale ranging from 0 (no plaque) to 5
(complete plaque coverage). The clinical examiner estimates the numerical value or score based on
visual observation of the plaque. Unfortunately, there are drawbacks to this approach. First, the scale
is non-linear with respect to plaque area coverage. Second, the application of the scale is subjective
by nature. Therefore, an objective method of measuring the amount of plaque on teeth represents a
significant improvement in the science of plaque measurement.
1. Scope ment is performed using an illuminator system that provides
controlled illumination on the teeth and surrounding tissue. A
1.1 This method covers the procedure, instrumental
DigitalStillCamera(DSC)isusedtocapturethedigitalimage.
requirements, standardization procedures, material standards,
measurement procedures, and parameters necessary to make 1.4 Data acquired using this method may be used to assess
precisemeasurementsofdentalplaqueontheteethrevealedby personal plaque coverage for the purposes of identifying
fluorescence.Inparticularitismeanttomeasuretheamountof overallhealthstatus,healthstatusatspecificsitesinthemouth,
plaque and plaque coverage on human teeth. or to track changes in personal health status for individuals
over time. Pooled data may be used to assess plaque coverage,
1.2 Digital images are used to measure the coverage of
health, disease among populations in epidemiological surveys,
dental plaque on the teeth using discrimination analysis. All
evaluation of comparative product efficacy, or safety and
localized discoloration, such as stains, inclusions,
treatment response in clinical trials involving plaque coverage
pigmentations, etc., may be separated from the measurement
or disease.
and the analysis. All other non-relevant parts, such as teeth,
tongue, spaces, dental restorations or prostheses, etc., must be 1.5 The apparatus, measurement procedure, and analysis
separated from the measurement and the analysis. technique described herein are generic. The intent is not to
NOTE 1—This procedure may not be applicable for all types of dental
excludeaspecificapparatus,measurementprocedure,oranaly-
work.
sis technique.
1.3 The broadband reflectance factors of the teeth and
1.6 The values stated in SI units are to be regarded as
surrounding tissue are measured. The colorimetric measure-
standard. The values in parenthesis are for information only.
1.7 This standard does not purport to address all of the
This test method is under the jurisdiction of ASTM Committee E12 on Color
safety concerns, if any, associated with its use. It is the
andAppearance and is the direct responsibility of Subcommittee E12.06 on Image
responsibility of the user of this standard to establish appro-
Based Color Measurement.
priate safety and health practices and determine the applica-
Current edition approved Feb. 1, 2009. Published June 2009. DOI: 10.1520/
E2670-09. bility of regulatory limitations prior to use.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2670−09
2. Referenced Documents 3.2.7 disclosing agent, n—a dye which binds to, adsorbs to
2 or is physically retained in the plaque matrix.
2.1 ASTM Standards:
3.2.7.1 Discussion—Common disclosing agents are
E179Guide for Selection of Geometric Conditions for
fluorescein, erythrosine, fast green, and methlyene blue.
Measurement of Reflection and Transmission Properties
3.2.8 facial surfaces, n—the surfaces of teeth and gingiva
of Materials
that are oriented outward toward the lips (labial) and cheeks
E284Terminology of Appearance
(buccal), and facing away from the tongue or roof of the
E1345Practice for Reducing the Effect of Variability of
mouth.
Color Measurement by Use of Multiple Measurements
E1767Practice for Specifying the Geometries of Observa-
3.2.9 in-vivo, adj—within a living body.
tion and Measurement to Characterize the Appearance of
3.2.9.1 Discussion—Pertaining to measurements made in a
Materials
living body.
2.2 ISO Publications:
3.2.10 NIR cutoff filter, n—anopticalfilterthatdoesnotpass
ISO 17321-1Colour characterization of digital still cameras
wavelengths longer than 700 nm.
(DSCs) — Part 1: stimuli, metrology, and test procedures
3.2.11 posterior teeth, n—the large teeth in the back of the
ISO/IEC 15444-1:2000–JPEG2000Information technology
mouth.
— JPEG 2000 image coding system — Part 1: Core
coding system, commonly known as JPEG 2000 jp2 file
4. Summary of Test Method
format
4.1 This method describes the procedures for in-vivo broad
2.3 ISCC Publications:
bandreflectometryofthesubjects’teeth,plaque,andsurround-
TechnicalReport2003-1GuidetoMaterialandTheirUsein
ing tissue.
Color Measurement
4.2 This method describes the standardization of the mea-
3. Terminology
surement instrumentation used to measure a subject’s teeth.
3.1 Terms and definitions in Terminology E284 are appli-
4.3 The DSC captures and stores the RGB values of the
cable to this test method.
images. The data from the reflectance measurements are
3.2 Definitions: Terms included in this section that are analyzed to discriminate between plaque, teeth, and surround-
peculiar to this standard.
ing tissue.
3.2.1 angle of incidence, n—θ and θ optional, the polar
1 2
4.4 Discrimination analysis allows one to calculate percent-
angle between the central ray of the illuminator(s), I and I ,
1 2
age of plaque coverage on teeth.
and the Z axis, which is the optical axis of the camera.
4.5 Guidelines are given for disclosing of plaque.
3.2.1.1 Discussion—These are shown in Fig. A1.1.
3.2.2 anterior teeth, n—anterior teeth are the six upper and
5. Significance and Use
six lower front teeth; the anterior teeth consist of incisors and
5.1 The light reflected from the teeth and emitted from the
cuspids (canines).
plaqueontheteethiscapturedbyaDSC.Digitaldataextracted
3.2.3 bit depth, n—the number of digital bits used to store
from the images can be used to discriminate and classify
information contained in each color channel of each pixel.
pixels. Monitored over time, changes in plaque coverage can
3.2.3.1 Discussion—Thebitdepthdeterminesthemaximum
be observed. An example is a clinical study of the efficacy of
number of colors that may be encoded by the system. For
tooth brushes to remove dental plaque.
example, a 24 bit system comprising 8 bits per channel can
8 8 8 5.2 Assessingthequantityandcoverageofdentalplaqueon
encode 2 ×2 ×2 or about 17 million colors; far more than
teeth can be used to optimize the design of products and
are distinguishable by the human observer.
procedures intended to reduce dental plaque coverage.
3.2.4 biofilm, n—acomplexaggregationofmicroorganisms.
5.3 Clinical assessment, for example, the modified Turesky
3.2.4.1 Discussion—Biofilms have been implicated in the
5,6
PlaqueIndex, isasubjective,non-linear,integerbasedscale
formulation of dental plaque and gingivitis.
that may require extensive examiner training and recertifica-
3.2.5 canine,n—thethirdtoothfromthecenterofthemouth
tion. The method described here provides increased precision,
towards the back of the mouth; these are the front teeth that
repeatability, and reproducibility in comparison to other meth-
have one rounded or pointed edge used for biting.
ods.
3.2.6 dentalplaque,n—abiofilmconsistingofbacteriainan
5.4 This procedure is suitable for use in research and
intrabacterial matrix, which adheres to teeth.
development, marketing claims and advertising, comparative
product analysis, and clinical trials.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Turesky S., Gilmore, N. D., Glickman I., “Reduced plaque formation by the
the ASTM website. chloromethylanalogueofVitaminC,” Journal of Periodontology,Vol.41,1970,pp.
Available from International Imaging Industry Association (13A), 701 41-43.
Westchester Ave., Suite 317W, White Plains, NY 10064, www.13A.org. QuigleyG.A.,andHeinJ.W.,“Comparativecleansingefficiencyofmanualand
Available from ISCC, Inter-Society Color Council, 11491 Sunset Hills Rd., power brushing,” Journal of the American Dental Association, Vol. 65, 1962, pp.
Reston, VA 20190, www.iscc.org. 26-29.
E2670−09
6. Interferences
6.1 The interferences identified below may be eliminated
andproblemsavoidedbycontrollingandregulatingeachfactor
within the constraints of the allowable experimental error. The
values and limits for these factors are typically determined
experimentally. If the standard laboratory conditions listed
below change during the test or from test to test by an
appreciable amount these conditions may cause interferences,
andtheaccuracyandprecisionrequirementsofthistestmethod
may not be achieved. In some cases these effects may only be
observed during the performance of the test.
6.1.1 Factors Affecting Test Results—The following factors
FIG. 1Subject Positioned in Chin Rest
are known to affect the test results.
6.1.1.1 Extraneous Radiation—Light including near infra-
redfromsourcesotherthantheilluminator(s)mustbeshielded
from the test apparatus.
6.1.1.2 Vibrations—Mechanicaloscillationsthatcausecom-
ponents of the apparatus to move relative to one 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
standardization, calibration, and verification plaques, and the
apparatus spectral response function.
6.1.1.4 Power Input Fluctuations—Large changes in the
FIG. 2Chin Rest
line frequency or supply voltage may cause the apparatus to
report erroneous results.
6.1.2 Retractors—Thesurfacefinishoftheretractorsaffects
the experimental test results. It has been determined that a
glossy finish on the surface of the retractors may introduce a
bias into the test results.
6.2 Standardization—The system must allow for successful
standardization. If the system cannot be standardized, a series
ofchecksmustbeperformed(lighting,camera,etc.)toidentify
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 FIG. 3Matte Lip Retractors
component from being used, or to exclude any type of
instrumentthatmaybeavailablecommercially.Between4and
6 different components or component assemblies are required
source must be stable with time and have adequate energy at
to accomplish the measurement.
the wavelengths of interest. The illumination must excite the
7.2 Geometry—The geometry of the system is 45:0 as
disclosing agent. Commonly used light sources include incan-
recommended in Practice E1767. The DSC System Geometry
descent lamps, either operated without filters or filtered to
(Coordinate System) and Angular Convention are shown in
simulate standard illuminants, flashed or continuous-wave
Fig. A1.1, included in Annex A1.
xenon-arc lamps, and discrete monochromatic or polychro-
7.3 Components—A block diagram of component assem- matic sources, such as light emitting diodes (LEDs).
blies is shown in Fig. A1.2, included in Annex A1. 7.3.3 Sample Plane Holder—The sample plane holder pro-
7.3.1 Source IlluminationAssembly—Containstheillumina- vides a secure mount so that it positions the subject’s incisors
tion source and associated optics to produce irradiance, E,on normaltotheZaxisandcenteredalongtheXandYaxes.This
the sample over a specified spot area, designated A.Adiagram must be done so that the teeth are presented to the DSC in a
ofthecomponentsofatypicalilluminationsystemisshownin repeatable and reproducible manner. The sample mount must
Fig. A1.3, included in Annex A1. bekeptunobtrusivesothatitis“friendly”andnotintimidating
7.3.2 Spectral Power Distribution—The exact spectral na- tothesubjects.Achinrestcanbeusedtopreciselypositionthe
ture of the illuminator is immaterial for the measurement. The subjects relative to the instrumentation (Fig. 1). The subject
E2670−09
places their chin on a chin rest which is a quartercup shaped product. It can also be used to assess the status of health of an
rig, as shown in Fig. 2, chin rest. individual or a group.
7.3.4 Lip Retractors (Fig.3)areusedtoexposethemajority 8.1.2 Aclinicaltrialusuallyhasentrancecriteria.Volunteers
of the subject’s teeth to the DSC. The subject holds the head who meet clinical trial entrance criteria and provide informed
straight, join the tips of the upper and lower incisors together, consent are chosen. For example, the clinical trial may require
and places the tongue against the top of the mouth. The facial subjects of a particular age.
surface of the central incisors should be aligned with a line 8.1.3 Subjects may be excluded from participation in a
marked on the chin rest indicating the center along the X axis. clinical trial due to restorative dentistry involving facial
7.3.5 Detector Optical Elements: surfaces of the anterior teeth.
7.3.5.1 The typical detector optical elements are shown in
8.2 Sampling:
Fig. A1.4, included in Annex A1.
8.2.1 The subjects are to disclose the plaque using the
7.3.6 Digital Still Camera—
...