1、Designation: E2466 06 (Reapproved 2011)Standard Test Method forColorimetry of Teeth Using Digital Still Camera Technology1This standard is issued under the fixed designation E2466; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONTooth color is an important parameter used to ascertain certain medical and esthetic information.CIE colorim
3、etric values for the teeth are derived from the native RGB signals generated by a digitalstill camera, DSC, by broadband measurement of the reflectance of teeth. The illumination angle is 45degrees and CIELAB colorimetric coordinates are computed using equations contained in PracticeE308. This test
4、method, E2466, specifies the procedure used for the measurement of tooth colorin-vivo and in-vitro with illumination at 45 degrees relative to the sample plane which is also thenormal of the mouth, under an approximate equal energy spectrum. This test method is appropriate foranterior and posterior
5、teeth.1. Scope1.1 This test method covers the procedure, instrumentalrequirements, standardization procedures, material standards,measurement procedures, and parameters necessary to makeprecise measurements of in-vivo tooth color and tooth white-ness. In particular it is meant to measure the color o
6、f teeth inselected human subjects.1.2 Digital images are used to evaluate tooth color of bothposterior and anterior dentition (teeth). All other non-relevantparts, such as gums, spaces, etc., must be separated from themeasurement and the analysis.All localized discoloration; suchas stains, inclusion
7、s, etc., may be separated from the measure-ment and the analysis.1.3 The broadband reflectance factors of teeth are measured.The colorimetric measurement is performed with a digital stillcamera while using an illuminator(s) that provides controlledillumination on the teeth. The measured data from a
8、digitalimage are captured using a DSC. This test method is particu-larly useful for the gamut of tooth color which is:1.3.1 CIE L* from 55 to 95,1.3.2 CIE a* from 3 to 12,1.3.3 CIE b* from 8 to 25 units.1.4 The wavelengths for this test method include thatportion of the visible spectrum from 400 to
9、700 nm.1.5 Data acquired using this test method is for comparativepurposes used during clinical trials or other types of research.1.6 This test method is designed to encompass natural teeth,artificial teeth, restorations, and shade guides.NOTE 1This procedure may not be applicable for all types of d
10、entalwork.1.7 The apparatus, measurement procedure, data analysistechnique are generic, so that a specific apparatus, measure-ment procedure, or data analysis technique may not be ex-cluded.1.8 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for i
11、nformationonly.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use
12、.2. Referenced Documents2.1 ASTM Standards:2D2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesE179 Guide for Selection of Geometric Conditions forMeasurement of Reflection and Transmission Properties ofMaterialsE284 Terminology of Ap
13、pearanceE308 Practice for Computing the Colors of Objects by1This test method is under the jurisdiction of ASTM Committee E12 on Colorand Appearance and is the direct responsibility of Subcommittee E12.06 on ImageBased Color Measurement.Current edition approved June 1, 2011. Published June 2011. Ori
14、ginallyapproved in 2006. Last previous edition approved in 2006 as E2466 - 06. DOI:10.1520/E2466-06R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards
15、 Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Using the CIE SystemE313 Practice for Calculating Yellowness and WhitenessIndices from Instrumentally Measured Color CoordinatesE1345 Practice
16、for Reducing the Effect of Variability ofColor Measurement by Use of Multiple MeasurementsE1767 Practice for Specifying the Geometries of Observa-tion and Measurement to Characterize the Appearance ofMaterials2.2 ISO Publications:3ISO 17321-1, Colour characterization of digital still cam-eras (DSCs)
17、 Part 1: Stimuli, metrology, and test proce-dures2.3 ISCC Publications:4Technical Report 2003-1 Guide to Material Standards andTheir Use in Color Measurement3. Terminology3.1 Terms and definitions in Terminology E284 are appli-cable to this test method.3.2 DefinitionsTerms included in this section a
18、re peculiarto this standard.3.2.1 angle of incidence, nu1and optional u2, the polarangle between the central ray of the illuminator(s), I1and I2,and the Z axis which is normal to the camera. See Fig. A1.1.3.2.2 anterior teeth, nanterior teeth are the six upper andsix lower front teeth; the anterior
19、teeth consist of incisors andcuspids (canines).3.2.3 bit depth, nthe number of digital bits used to storeinformation contained in each pixel.3.2.3.1 DiscussionThe higher the depth, the more colorsare in an image. With 8 bit-per-channel color, there are a totalof 256 bits available for color represen
20、tation in each of the R,G, B channels. RGB 8 bit-per-channel color is sometimescalled “24 bit color.”3.2.4 canine, nthe third tooth from the center of themouth towards the back of the mouth; these are the front teeththat have one rounded or pointed edge used for biting.3.2.5 facial surfaces, nof or
21、toward the face, used todesignate the side of the tooth that is facing away from thetongue side.3.2.6 in-vitro, adj or advin an artificial environmentoutside of the human body.3.2.7 in-vivo, adj or advwithin a living body; that is,measurements made of a living tooth in a living body.3.2.8 maxillary
22、anterior teeth, nthe four front upperincisors and the canine teeth. See Fig. A1.5.3.2.9 native digital still camera spectral response function,nthe function relating scene radiance to image intensity of animaging system is called the digital still camera spectralresponse function.3.2.10 polarization
23、, nthe orientation of the vibration pat-tern of light waves in a singular plane.3.2.11 polarizer filter, na component that blocks one ofthe two planes of vibration of an electromagnetic wave,producing linearly polarized light.3.2.11.1 DiscussionA polarizing filter can be used insunglasses to reduce
24、glare.3.2.12 posterior teeth, nposterior teeth are the large teethin the back of the mouth.3.2.13 spatial whitening response, nthe evaluation ofcolor or color change used to determine unit dosing.4. Summary of Test Method4.1 This test method describes the procedures for broadbandreflectance measurem
25、ent of teeth, in-vivo and in-vitro. Thestandardization of the instrumentation used to measure asubjects teeth is defined. The basis for the selection ofspecimens and the measurement protocol given. The data fromthe reflectance measurements are converted to colorimetricvalues. The results are reporte
26、d in terms of CIE tristimulusvalues, other colorimetric coordinate system values, and colo-rimetric indices.5. Significance and Use5.1 The light reflected from the facial anterior teeth can beused to calculate color coordinates. Monitored over time,changes in color can be observed. These data reveal
27、 informa-tion about the efficacy of a product, treatment study, orepidemiology of tooth color. For example, clinical studies ofconsumer tooth whitening systems evaluate the efficacy ofmanufacturers products.5.2 The change in color of the facial surfaces of anteriorteeth can be used to optimize the e
28、fficacy of tooth whiteningsystems. For example, the data can provide the answer thequestion: “What is the optimum percentage of whitening agentin a consumer tooth whitening system?”5.3 This procedure is suitable for use in research anddevelopment, marketing studies, comparative product analy-ses, an
29、d clinical trials.5.4 Prior research shows that a popular visual assessmentmethod of determining tooth color, changes in tooth color, andwhiteness among clinicians yields less than desirable results(1-4). These assessment tools are designated “shade guides.”They consist of tooth-shaped, synthetic ob
30、jects in the form ofteeth all of slightly different colors or different shades from oneanother. A “shade” is generally regarded as a color slightlydifferent from a reference color (on a comparative basis). Thecolors of the synthetic teeth in these “shade guides” do notprogress linearly as observed v
31、isually or logically in a CIEcolorimetric coordinate system,5and they are metameric to realteeth.5.5 TranslucencyHuman teeth are translucent and thedegree of translucency varies widely between subjects. How-ever, translucency does not vary over the short term and is nottherefore a consideration in t
32、his test method.3Available from International Imaging Industry Association (I3A), 701Westchester Avenue, Suite 317W, White Plains, NY 10604, 914-285-4933,isotc42i3a.org.4Available from ISCC, Inter-Society Color Council, 11491 Sunset Hills Rd.,Reston, Va, 20190.5Available from University of Michigan,
33、 http:/www.lib.umich.edu/dentlib/Dental_tables/Colorshadguid.html.E2466 06 (2011)26. Interferences6.1 If the standard laboratory conditions listed in 6.2 changeduring the test or from test to test by an appreciable amount,these conditions may cause interferences, and the accuracy andprecision requir
34、ements of this test method may not beachieved. In some cases these effects may only be observedduring the performance of the test.6.2 Factors Effecting Test ResultsThe following factorsare known to affect the test results.6.2.1 Environmental:6.2.1.1 Extraneous RadiationExtraneous light from othersou
35、rces and near-infrared (NIR) radiations must be shieldedfrom the test apparatus.6.2.1.2 VibrationsMechanical oscillations that causecomponents of the apparatus to move independently from oneanother may cause errors in test results.6.2.1.3 Thermal ChangesTemperature changes occurringduring a test or
36、differences in temperature between testinglocations may affect the reflectance factor of the standardiza-tion, calibration, and verification plaques, and the apparatusspectral response function.6.2.1.4 Power Input FluctuationsLarge changes in theline frequency or supply voltage may cause the apparat
37、us toreport erroneous results.6.2.2 RetractorsThe surface finish of the retractors affectsthe experimental test results. It has been determined that aneutral (clear) finish on the surface of the retractors mayintroduce a bias into the test results.6.3 StandardizationThe system must allow for success
38、fulstandardization.6.4 Equipment OperationIf the system cannot be stan-dardized, a series of checks must be performed (lighting,camera, etc.) to identify the reason. The component of thesystem in error will be adjusted or replaced to bring the systemback into calibration.6.5 Controlling Factors:6.5.
39、1 These interferences may be eliminated and problemsavoided by controlling and regulating each factor within theconstraints of the allowable experimental error. The values andlimits for these factors are typically determined experimentally.7. Apparatus7.1 GeneralThe components described in this sect
40、ion aredescribed generically. The intention is not to exclude anycomponent from being used, or to exclude any type ofinstrument that may be available commercially. Between 4 and6 different components or component assemblies are requiredto accomplish the measurement.7.2 GeometryThe geometry of the sy
41、stem is 45:0 asdescribed in Practice E1767 and Guide E179. The DSC SystemGeometry (Coordinate System) and Angular Convention areshown in Fig. A1.1.7.3 ComponentsA block diagram of these componentassemblies is shown diagrammatically in Fig. A1.2.7.3.1 Source Illumination AssemblyContains the sourceof
42、 illumination and associated optics to produce irradiance, E,on the sample over a specified spot area, designated A. Thesource is broadband and continuous in nature. A diagrammaticrepresentation of the components of a typical Source Illumi-nation Assembly Unit is shown in Fig. A1.3.7.3.2 Source Beam
43、(s)A collimated or slightly convergingbeam(s) focused on the sample plane. Since the shape andposition of the specimens being measured vary widely, a smallconvergence angle minimizes local variations in intensity. Twobeams located at 45 relative to the normal of the sample planeare required to exami
44、ne posterior teeth (on each side of themouth) and to achieve the uniformity requirements.7.3.3 PositionTypically the Source Illumination Assem-blies are in a fixed position relative to the sample (Subject)holder and the DSC. Therefore, small variations in u areminimized. The angle u is the subtended
45、 angle between theSource Illumination Assembly Units and the DSC. Refer toFig. A1.1.7.3.4 Source Optical ElementsThe optical elements mustcondition the radiation from the source so that it is spatiallyuniform within 610 %. The distance, d, from the DSC to thesample plane must be selected to maintain
46、 the uniformityrequirements. Refer to Fig. A1.6.7.3.5 Spectral Power DistributionThe exact spectral na-ture of the illuminator is immaterial for the measurement ofteeth and non-fluorescent specimens so long as the source isstable with time and has adequate energy at all wavelengths inthe region requ
47、ired for measurement.An approximation to D50provides an equal energy spectrum over the area of interest forDSCs. Commonly used light sources include incandescentlamps, either operated without filters or filtered to simulatestandard illuminants, flashed or continuous-wave xenon-arclamps and discrete
48、pseudo-monochromatic sources, such aslight emitting diodes (LEDs).7.3.6 PolarizationThe linear polarizer provides and con-trols the polarization state of the incident light. This polarizeron the illuminators plus a cross polarizer filter on the lenssystem of the DSC eliminates glare caused by reflec
49、tion of thesubjects teeth during imaging. Wavelength range, extinctionratio, transmittance, and beam deviation are important param-eters and must be selected.7.3.7 Heat Rejection FiltersThese filters remove unde-sired near-infrared (NIR) radiation including heat that ad-versely affects the subject and provide spectral shaping of thespectral power distribution of the source illumination.7.3.8 Selective Blue FiltersThese filters condition thespectral power distribution of the illumination so that thespectral power distribution is similar to a
