1、Dentistry Guidance on colour measurement PD ISO/TR 28642:2016 BSI Standards Publication WB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06National foreword This Published Document is the UK implementation of ISO/TR 28642:2016. The UK participation in its preparation was entrusted by Technical
2、Committee CH/106, Dentistry, to Subcommittee CH/106/2, Prosthodontic materials. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its co
3、rrect application. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 91145 3 ICS 11.060.10 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of the Standards Policy
4、and Strategy Committee on 31 December 2016. Amendments/corrigenda issued since publication Date Text affected PUBLISHED DOCUMENT PD ISO/TR 28642:2016 ISO 2016 Dentistry Guidance on colour measurement Mdecine bucco-dentaire Directives relatives au mesurage de la couleur TECHNICAL REPORT ISO/TR 28642
5、Reference number ISO/TR 28642:2016(E) Second edition 2016-12-01 PD ISO/TR 28642:2016 ISO/TR 28642:2016(E)ii ISO 2016 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or u
6、tilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copy
7、right office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyrightiso.org www.iso.org PD ISO/TR 28642:2016 ISO/TR 28642:2016(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Visual and inst
8、rumental colour assessment . 3 4.1 Devices . 3 4.2 Setting . 4 4.2.1 llluminant . 4 4.2.2 Standard observer 4 4.2.3 Geometric conditions . 4 4.2.4 Illuminance . 4 4.2.5 Visual angle of subtense 4 4.2.6 Background. 4 4.2.7 Surround . 4 4.2.8 Additional/other considerations . 5 5 Observers . 5 5.1 Eva
9、luation of colour competency of candidate for observer in studies on acceptability or perceptibility in dentistry . 5 5.1.1 Ishihara colour blindness test 5 5.1.2 Farnsworth-Munsell 100 hue test . 5 5.1.3 Test for colour discrimination competency in dentistry . 5 5.2 Guidelines for observer selectio
10、n for acceptability or perceptibility evaluation in dentistry . 5 5.2.1 General tests 5 5.2.2 Test for colour discrimination competency in dentistry . 5 5.2.3 Testing intervals for qualified observers 6 6 Testing of acceptability and perceptibility thresholds . 6 6.1 Tissues and materials to be test
11、ed for perceptibility and acceptability thresholds . 6 6.2 Test methods . 6 6.2.1 Visual judgments . 6 6.2.2 Instrumental evaluation 6 7 Application and interpretation . 6 7.1 Colour compatibility 7 7.1.1 Colour compatibility between dental material and human tissues . 7 7.1.2 Colour compatibility b
12、etween dental materials . 7 7.1.3 Coverage error of dental shade guides . 7 7.2 Colour stability 7 7.2.1 Colour stability during fabrication/at placement . 7 7.2.2 Colour stability after aging and staining 12 7 7.3 Colour interactions 7 7.3.1 Colour shifting of aesthetic restorative materials 13 14
13、7 7.3.2 Masking potential of opaque materials 8 8 Reporting of colour and colour difference assessment . 8 8.1 Illuminant 8 8.2 Object 8 8.3 Observer/instrument 8 8.3.1 Observer 8 8.3.2 Instrument 9 Bibliography .10 ISO 2016 All rights reserved iii Contents Page PD ISO/TR 28642:2016 ISO/TR 28642:201
14、6(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for whic
15、h a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all ma
16、tters of electrotechnical standardization. The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This
17、document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or a
18、ll such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users a
19、nd does not constitute an endorsement. For an explanation on the meaning of ISO specific terms and expressions related to conformit y assessment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following UR
20、L: www.iso.org/iso/foreword.html. The committee responsible for this document is ISO/TC 106, Dentistry, Subcommittee SC 2, Prosthodontic materials. This second edition cancels and replaces the first edition (ISO/TR 28642:2011), which has been technically revised.iv ISO 2016 All rights reserved PD IS
21、O/TR 28642:2016 ISO/TR 28642:2016(E) Introduction The colour appearance of teeth and other dentistryrelated tissues need to be matched and reproduced in order to achieve acceptable aesthetics in an efficient manner. Three major groups of issues, related to colour compatibility, colour stability and
22、colour interactions, are identified and considered in this document. Interpretation of colour differences associated with these three groups through 50:50 % perceptibility and acceptability visual thresholds is suggested. Colour is a psychophysical phenomenon that is assessed by both visual and inst
23、rumental methods. Other elements of appearance, including gloss and translucency, affect aesthetics and may influence the characterization of colour appearance. The International Commission on Illumination (CIE) colour difference formulae and resources, in particular CIE Pub No 15.3, were used in th
24、is document. ISO 2016 All rights reserved v PD ISO/TR 28642:2016 Dentistry Guidance on colour measurement 1 Scope This document identifies three types of topics related to shade conformity and interconvertibility of monochromatic and polychromatic tissues and materials related to the discipline of d
25、entistry; it describes visual and instrumental methods for assessment of these topics. This document suggests interpretation of the findings through colour difference thresholds and provides guidelines for future standardization related to dental shade conformity and interconvertibility. It also inc
26、ludes guidelines related to colour vision of persons undertaking visual colour assessments and instructions for reporting of colour and colour difference assessments. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitute
27、s requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 1942, Dentistry Vocabulary ISO 11664-1, Colorimetry Part 1: CIE standard colorimetric observers 3 T erm
28、s a nd definiti ons For the purposes of this document, the terms and definitions given in ISO 1942 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/ /www.electropedia.org/ ISO Online bro
29、wsing platform: available at http:/ /www.iso.org/obp 3.1 colour difference single number or metric expressing the distance from complete match in colour or shade Note 1 to entry: A colour distance metric defined by the International Commission on Illumination (CIE) is called delta E (E). Note 2 to e
30、ntry: Two formulae for calculating E are recommended in this document: CIE 76 (denoted E* ab ) and CIEDE2000 (denoted E 00 ). 3.2 50:50 % perceptibility threshold of colour difference PT difference in colour that can be detected by 50 % of observers under controlled conditions, with the other 50 % o
31、f observers noticing no difference in colour between the compared objects Note 1 to entry: A nearly perfect colour match in dentistry is a colour difference at or below the 50:50 % perceptibility threshold. TECHNICAL REPORT ISO/TR 28642:2016(E) ISO 2016 All rights reserved 1 PD ISO/TR 28642:2016 ISO
32、/TR 28642:2016(E) 3.3 50:50 % acceptability threshold of colour difference AT difference in colour that is considered acceptable by 50 % of observers under controlled conditions, with the other 50 % of observers replacing or correcting the restoration Note 1 to entry: An acceptable colour match in d
33、entistry is a colour difference at or below the 50:50 % acceptability threshold. 3.4 colour standards in dentistry sets of polychromatic or monochromatic samples (tabs, chips, or patches), most frequently made of dental ceramic or resin (tooth shade guides), or silicone elastomer (skin shade guides
34、in maxillofacial prosthodontics) Note 1 to entry: The polychromatic and monochromatic samples are fabricated for the purposes of colour matching hard and soft oral tissues, and human skin (see Reference 2). 3.5 coverage error index that describes the mean of minimal colour differences (E* min ) betw
35、een the specimens of one set (e.g. a shade guide) to each specimen of another set (e.g. natural teeth) Note 1 to entry: The coverage error is calculated as the mean E* minfor all best matches as follows: n where n is the number of best matches. Note 2 to entry: The smaller the coverage error, the hi
36、gher the chances of successful shade matching. 3.6 tooth whitening change in tooth colour caused by bleaching or stainremoval agents and manifested by the increase in the value of lightness and the decrease of chroma 3.7 colour shifting change in perceived colour that is a sum of a blending effect a
37、nd an effect of physical translucency 3.7.1 colour shifting due to blending change in perceived colour of a material due to a change in surroundings Note 1 to entry: Colour shifting due to blending is a psychophysical phenomenon and is not modelled by the current CIELAB mathematical model; it is an
38、optical illusion, visually perceptible, but not quantifiable or measurable by any instrument. 3.7.2 colour shifting due to physical translucency change in colour of translucent dental restorations caused by surroundings and background (underlying layers of hard dental tissues or other restorative ma
39、terials) 3.8 opacity measure of the ability of a material to block the passage of light Note 1 to entry: A material with high opacity is one with low translucency/transparency.2 ISO 2016 All rights reserved PD ISO/TR 28642:2016 ISO/TR 28642:2016(E) 3.9 transparency physical property of allowing the
40、transmission of light through a material Note 1 to entry: A material with high transparency is one with low opacity. Note 2 to entry: Transparency is the extreme value of high translucency. Note 3 to entry: A transparent material allows light to pass through undiminished, while a negligible portion
41、of the transmitted light is scattered. 3.10 translucency ability of a material to allow light to pass through it Note 1 to entry: A material with high translucency is one with low opacity. Note 2 to entry: Translucent materials allow light to pass through only diffusely (they cannot be seen through
42、clearly). 3.11 gloss capacity of a surface to reflect more light in some directions than in others 3.12 specular gloss ratio of flux reflected in the specular direction to incident flux (i.e. the angle of the reflected light is equal and opposite to the angle of the incident beam) for a specified an
43、gle of incidence, source, and receptor angular aperture Note 1 to entry: These reflections normally have the highest reflectances (see References 2 and 3). 4 Visual and instrumental colour assessment 4.1 Devices Frequently used devices for visual and instrumental colour assessment in dentistry are s
44、pectrophotometers, spectroradiometers, colourimeters, imaging systems for traditional digital imaging and spectral imaging, viewing booths, and different types of handheld shade matching lights. Spectral measurement is performed using a spectrophotometer, a device designed to measure spectral transm
45、ittance and spectral reflectance of objects. Compared to colourimetric measurements, spectral measurements enable more flexible measurements to calculate colour differences under arbitrary illuminants and observers. Spectrometer parameters relevant for dentistry include wavelength range, wavelength
46、resolution, integration time and spectral sensitivity. In addition to these parameters, method of measurement, technology and geometry have to be taken in account when selecting the equipment or designing a system to measure spectra. Spectral measurement accuracy can be measured in terms of root mea
47、n square error (rms) or degree of correlation between spectral data, and other weighted spectral measurements that emphasize the wavelength that are more relevant for human vision. Having spectral measurements of both reference and test samples, it is possible to calculate how robust is the pair of
48、samples to changes in illumination and observers by means of index of metamerism. ISO 2016 All rights reserved 3 PD ISO/TR 28642:2016 ISO/TR 28642:2016(E) 4.2 Setting Colour assessment requires careful control of factors that affect colour perception and/or measurement. The following aspects of the
49、test conditions should be specified in reporting visual assessments of colour appearance. 4.2.1 llluminant The characteristics of the light source or sources that illuminate the object of a colour measurement as specified preferably by the spectral power distribution (SPD) and correlated colour temperature (CCT) specified according to ISO 116442. CIE standard illuminant D65 (representing noon daylight, CCT of 6500 K) with a Colour Rendering Index (CRI) of 90 or greater is recommend
