1、 ISO 2017 Dentistry Test methods for machining accuracy of computer- aided milling machines Mdecine bucco-dentaire Mthodes dessai pour lexactitude dusinage des fraiseuses commande numrique TECHNICAL REPORT ISO/TR 18845 Reference number ISO/TR 18845:2017(E) First edition 2017-06 ISO/TR 18845:2017(E)i
2、i ISO 2017 All rights reserved COPYRIGHT PROTECTED DOCUMENT ISO 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or postin
3、g 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 copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41
4、 22 749 09 47 copyrightiso.org www.iso.org ISO/TR 18845:2017(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Recommendations 1 5 Test methods . 1 5.1 Target restorations 1 5.2 Apparatus 2 5.3 Preparation of three-dimensional data . 2 5.4 Machining of
5、restorations 6 5.5 Evaluation of accuracy 7 5.5.1 General 7 5.5.2 Class II inlay . 7 5.5.3 Crown 9 5.5.4 Four-unit bridge 11 6 Test report 12 7 Information .13 Annex A (informative) Flow chart of test method 14 Annex B (informative) Test methods using coordinate measuring machine (CMM) .15 Annex C (
6、informative) Contents of test report.24 Bibliography .28 ISO 2017 All rights reserved iii Contents Page ISO/TR 18845:2017(E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing Internation
7、al Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which 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,
8、 also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters 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
9、 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This 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 th
10、e elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all 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 r
11、eceived (see www .iso .org/ patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assess
12、ment, as well as information about ISOs adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: w w w . i s o .org/ iso/ foreword .html. This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 9, Dent
13、al CAD/CAD systems.iv ISO 2017 All rights reserved ISO/TR 18845:2017(E) Introduction Dental CAD/CAM systems have been successfully used for the fabrication of indirect dental restorations such as inlays, crowns and bridges. The accuracy of these restorations is one of the most important factors for
14、their clinical success. This document provides standardized test methods to evaluate the machining accuracy of computer-aided milling machines which are used as a part of dental CAD/CAM systems and the information to be provided by the manufacturer. A flow chart of test method is shown in Annex A. T
15、here is another method to evaluate accuracy of the target restoration(s) using coordinate measuring machine (CMM) and software. Test methods using CMM are shown in Annex B. ISO 2017 All rights reserved v Dentistry Test methods for machining accuracy of computer-aided milling machines 1 Scope This do
16、cument specifies the test methods to evaluate the machining accuracy of computer-aided milling machines as a part of dental CAD/CAM systems, which fabricate dental restorations, e.g. inlays, crowns and bridges. 2 Normative references The following documents are referred to in the text in such a way
17、that some or all of their content constitutes 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 18739, Dentistry Vocabulary
18、of process chain for CAD/CAM systems 3 T erms a nd definiti ons For the purposes of this document, the terms and definitions given in ISO 1942, ISO 18739 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: av
19、ailable at h t t p :/ www .electropedia .org/ ISO Online browsing platform: available at h t t p :/ www .iso .org/ obp 3.1 computer-aided milling machine computer-aided machining device designed for subtractive manufacturing of dental prostheses using rotary instruments for cutting and grinding 4 Re
20、commendations The accuracy of target restoration(s) should be evaluated using the test methods described in Clause 5. The test method and its results should be provided in the instruction for use, the technical manual or other means. When the machining accuracy is affected by the material, appropria
21、te material(s) should be tested. Testing should be performed on each material type that the manufacturer indicates for use by the device. 5 Test methods 5.1 Target restorations Three types of restorations, a) Class II inlay, b) crown and c) four-unit bridge, are the targets of this document. Choose
22、the type(s) following the applicable restoration(s) specified by the manufacturer. If any of the three restorations is not specified as applicable by the manufacturer, this restoration TECHNICAL REPORT ISO/TR 18845:2017(E) ISO 2017 All rights reserved 1 ISO/TR 18845:2017(E) is eliminated from the ta
23、rget. In other words, the fabrication of the restoration(s) and the accuracy evaluation are carried out only for the applicable restoration(s) specified by the manufacturer. NOTE This test method is designed adopting the same principle as the examination method of clinical marginal adaptation. The c
24、linical adaptation is examined checking the discrepancy between the restoration and the cavity margin or between it and the shoulder margin of abutment. The metal die for crown and four-unit bridge is used as same as ISO 12836. 5.2 Apparatus Two types of metal dies given in Figure 1 (Class II inlay)
25、 and Figure 2 (crown and four-unit bridge dies) are used both for the preparation of three-dimensional data (manufacturing data set) and the evaluation of the accuracy of restorations. As shown in Figure 1 and Figure 2, these dies consist of a non-malleable metal die and one or more removable struct
26、ure(s) used for the evaluation of accuracy. Each die should be measured using a measuring device with accuracy of 2 m to confirm the specified shape and dimensions. The measured data are used to prepare the three-dimensional data (see 5.3). The diameter of the removable occlusal part should be not l
27、ess than the diameter of abutment and the difference of diameter should be not more than 10 m. The surface roughness (Sa) of the die, excepting the surfaces which do not come in contact with the test specimens/machined restorations, should be less than 2 m. Refer to ISO 25178-2 and other parts for t
28、est methods. If a mark for reference point is necessary, a groove and/or a ridge may be placed on the part, but should be placed so as to not influence the evaluation of the results according to 5.5. The shapes and sizes of test specimen of the crown and the bridge should conform to Figure 3 (crown)
29、 and Figure 4 (bridge). One proximal-side of crown and bridge should have a flat plane to orient their position. NOTE 1 An example of the machining device to fabricate the dies is Vertical Center NEXUS 410B 1) . NOTE 2 Coordinate measuring machine (CMM) can be useful to measure the size of die. An e
30、xample of a CMM is America Strato-Apex 574 2) . 5.3 Preparation of three-dimensional data To fabricate the target restorations, a design data set (STL data) for each of the restorations should be prepared. This design data set should then be processed by the CAM software to prepare the manufacturing
31、 data set. The design data set should not be modified by the CAM software. The dimensions of any surfaces in contact with the die surfaces are obtained from the measuring process in 5.2. Other dimensions are determined from Figure 3 and Figure 4. The design data set should be prepared to ensure that
32、 the restoration comes in contact with the die without an allowance for cement space. 1) Vertical Center NEXUS 410B is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of thi
33、s product. 2) America Strato-Apex 574 is an example of a suitable product available commercially. This information is given for the convenience of users of this document and does not constitute an endorsement by ISO of this product.2 ISO 2017 All rights reserved ISO/TR 18845:2017(E) Dimensions in mi
34、llimetres Key 1 metal die 2 removable part 3 positioning pin 4 fixing screw Figure 1 Die for class II inlay specimen ISO 2017 All rights reserved 3 ISO/TR 18845:2017(E) Dimensions in millimetres Key 1 metal die 2 abutment 3 removable occlusal part 4 removable shoulder d height of removable shoulder
35、Figure 2 Die for crown and bridge specimen4 ISO 2017 All rights reserved ISO/TR 18845:2017(E) Dimensions in millimetres Key 1 metal die 2 abutment 3 removable occlusal part 4 removable shoulder 5 test specimen NOTE The unspecified dimensions are determined using the measured data specified in the fi
36、rst paragraph of 5.2. Figure 3 Test specimen of crown ISO 2017 All rights reserved 5 ISO/TR 18845:2017(E) Dimensions in millimetres Key 1 metal die 2 abutment 3 removable occlusal part 4 removable shoulder 5 test specimen NOTE The unspecified dimensions are determined using the measured data specifi
37、ed in the first paragraph of 5.2. Figure 4 Test specimen of bridge 5.4 Machining of restorations The prepared manufacturing data set should be input into the computer-aided milling machine following the manufacturers instruction. The CAM software should use the same configuration and parameters 6 IS
38、O 2017 All rights reserved ISO/TR 18845:2017(E) as is usually delivered. The target restoration should be machined using the material specimen (blank) following the manufacturers instruction. NOTE A manufacturer means a natural or legal person actually manufacturing a computer-aided milling machine
39、or a natural or legal person supplying necessary information to use the computer-aided milling machine. This test is carried out using a computer-aided milling machine maintained according to the manufacturers instruction. The evaluation of accuracy (see 5.5) is carried out using the restoration wit
40、hout any after treatment such as a sintering process. If any support structures are necessary for fabrication, they should not be positioned on the surface contacting the die and should be removed before the measurement. Fabricate six specimens for each of the target restorations. 5.5 Evaluation of
41、accuracy 5.5.1 General The accuracy of the restorations is expressed by the discrepancy between the margin of a restoration and baseline (cavity margin for inlays and abutment shoulder for crown and bridge). The measurement is carried out using a measuring device with an accuracy of 5 m, e.g. three-
42、 dimensional measuring microscope. The measured value should be expressed in millimetre to two decimal places. When two or more dies for each restoration type are prepared, the restoration should be fabricated using three-dimensional data based on the actual dimension of the die used for accuracy me
43、asurement. 5.5.2 Class II inlay Place the inlay in the cavity of a metal die and apply a load of 50 N on the centres of occlusal and proximal surfaces simultaneously and remove it after 30 s. Remove the load and examine where the margin of the inlay is located. When the occlusal margin of the inlay
44、is located higher than the occlusal baseline (occlusal margin of the die cavity), measure the discrepancy between the inlay margin and the baseline +A in Figure 5 a). Similarly, when the proximal margin of the inlay extends past the proximal baseline (proximal margin of the die cavity), measure the
45、discrepancy between the inlay margin and baseline +B in Figure 5 b). The measured values for both occlusal and proximal discrepancies are expressed as positive values. When the occlusal and proximal margins of the inlay are located at the same level of the baseline or beneath the baseline, remove th
46、e cavity base and place the inlay in the die cavity. Apply a load of 50 N on the occlusal and proximal surfaces simultaneously and remove it after 30 s. Measure the N on the occlusal and proximal surfaces simultaneously and remove it after 30 s. Measure the discrepancies between the occlusal inlay m
47、argin and the occlusal baseline A in Figure 5 c) and between the occlusal inlay margin and the proximal baseline B in Figure 4 d). The measured values are expressed as negative values. If the inlay margin is located at the same level of the baseline, the discrepancy is 0,00 mm. For both cases, measu
48、rements with and without metal die, the measurement should be carried out at three points for the occlusal discrepancy see Figure 5 e) and at four points for the proximal discrepancy see Figure 5 f). A discrepancy should be measured as horizontal discrepancy judging from the top. NOTE When a measuri
49、ng microscope is used, the discrepancy in the Z-direction cannot be precisely measured because of its poor focusing accuracy. The measured discrepancy data (three points for the occlusal discrepancy and four points for the proximal discrepancy) of one inlay are averaged to represent the discrepancy of that inlay. Calculate ISO 2017 All rights reserved 7 ISO/TR 18845:2017(E) the average of the six representative discrepancy values and the standard deviations to express the accuracy of the inl
