SIST EN ISO 18675:2023
(Main)Dentistry - Machinable ceramic blanks (ISO 18675:2022)
Dentistry - Machinable ceramic blanks (ISO 18675:2022)
This document specifies test methods for machinable ceramic blanks used for the fabrication of dental fixed restorations. This document also specifies the contents of the test report.
Zahnheilkunde - Maschinierbare Keramikblanks (ISO 18675:2022)
Dieses Dokument legt Prüfverfahren für maschinell bearbeitbare Rohlinge zur Herstellung fester dentaler Restaurationen fest. Dieses Dokument legt zudem den Inhalt von Prüfberichten fest.
Médecine bucco-dentaire - Ébauches en céramique usinables (ISO 18675:2022)
Le présent document spécifie les méthodes d’essai relatives aux ébauches en céramique usinables utilisées pour la fabrication de restaurations dentaires fixes. Le présent document spécifie également le contenu du rapport d’essai.
Zobozdravstvo - Keramični polizdelki, ki jih je mogoče obdelovati (ISO 18675:2022)
Ta dokument določa preskusne metode za strojno obdelane keramične surovce, ki se uporabljajo za izdelavo fiksnih zobnih obnov. Ta dokument določa tudi vsebino poročila o preskusu.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 18675:2023
01-april-2023
Zobozdravstvo - Keramični polizdelki, ki jih je mogoče obdelovati (ISO 18675:2022)
Dentistry - Machinable ceramic blanks (ISO 18675:2022)
Zahnheilkunde - Maschinierbare Keramikblanks (ISO 18675:2022)
Médecine bucco-dentaire - Ébauches en céramique usinables (ISO 18675:2022)
Ta slovenski standard je istoveten z: EN ISO 18675:2022
ICS:
11.060.10 Zobotehnični materiali Dental materials
SIST EN ISO 18675:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST EN ISO 18675:2023
---------------------- Page: 2 ----------------------
SIST EN ISO 18675:2023
EN ISO 18675
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2022
EUROPÄISCHE NORM
ICS 11.060.10
English Version
Dentistry - Machinable ceramic blanks (ISO 18675:2022)
Médecine bucco-dentaire - Ébauches en céramique Zahnheilkunde - Maschinierbare Keramikblanks (ISO
usinables (ISO 18675:2022) 18675:2022)
This European Standard was approved by CEN on 11 December 2022.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18675:2022 E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST EN ISO 18675:2023
EN ISO 18675:2022 (E)
Contents Page
European foreword . 3
2
---------------------- Page: 4 ----------------------
SIST EN ISO 18675:2023
EN ISO 18675:2022 (E)
European foreword
The text of ISO 18675:2022 has been prepared by Technical Committee ISO/TC 106 "Dentistry” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 18675:2022 by
Technical Committee CEN/TC 55 “Dentistry” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2023, and conflicting national standards shall be
withdrawn at the latest by June 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 18675:2022 has been approved by CEN as EN ISO 18675:2022 without any modification.
3
---------------------- Page: 5 ----------------------
SIST EN ISO 18675:2023
---------------------- Page: 6 ----------------------
SIST EN ISO 18675:2023
INTERNATIONAL ISO
STANDARD 18675
First edition
2022-05
Dentistry — Machinable ceramic
blanks
Médecine bucco-dentaire — Ébauches en céramique usinables
Reference number
ISO 18675:2022(E)
© ISO 2022
---------------------- Page: 7 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized 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 ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
---------------------- Page: 8 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Materials . 1
3.2 Properties . 2
3.3 Types of blanks . 2
3.4 Test piece . 2
4 Homogeneity of partially sintered zirconia blanks. 3
4.1 Classification . 3
4.2 Determination of the shrinkage factor, d . 3
4.2.1 Blanks characterized by one shrinkage factor for all three dimensions in
space . 3
4.2.2 Blanks characterized by two or three shrinkage factors . 5
4.3 Recommendations . 6
4.4 Test report . 6
5 Warpage . 7
5.1 Test method . 7
5.1.1 Large zirconia blanks . 7
5.1.2 Medium- and small-size zirconia blanks . 8
5.2 Recommendations . 8
5.3 Test report . 9
6 Dimensional stability post machining crystallization of glass ceramics .9
6.1 General . 9
6.2 Test method . 9
6.2.1 Sample preparation . 9
6.2.2 Characterization before heat treatment . 10
6.2.3 Heat treatment . 11
6.2.4 Characterization after heat treatment . 11
6.3 Test report .12
7 Machining damage .13
7.1 General .13
7.2 Test methods . 13
7.3 Test report .13
8 Machinability using the merlon fracture test .14
8.1 General . 14
8.2 Test method . 15
8.2.1 Dimensions of test geometries . 15
8.2.2 Machining . 16
8.2.3 Characterization of milled specimen . 16
8.3 Recommendations . 17
8.4 Test report . 17
Bibliography .19
iii
© ISO 2022 – All rights reserved
---------------------- Page: 9 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(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 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, 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 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 the 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 received (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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 9, Dental
CAD/CAM systems, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 55, Dentistry, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
© ISO 2022 – All rights reserved
---------------------- Page: 10 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
Introduction
A variety of ceramic blank materials are being used in machining systems for fabrication of various
restorations. Although all these materials can have different chemical and microstructural makeup,
there are some unique and common concerns for machining and performance of these materials.
Machining damage, minimum machined thickness, and machining tolerances all are common concerns
for these materials.
The overwhelming use of zirconia and alumina is in the form of green or partially sintered blanks with
shrinkage values of 20 % to 35 % by volume when sintered to full density. In order for the restoration
to be fabricated with proper accuracy, the blank density should be carefully measured and conveyed
to the computer controlled milling unit. This allows for proper oversizing and shrinkage to provide
an accurate fit. Furthermore, the blank should be homogeneous throughout the body, otherwise
differential shrinkage occurs resulting in significant warping and departure from linearity.
With respect to glass ceramics, a subset requires crystallization post-machining during which distortion
can occur placing the machined part out of the tolerance specified for the restoration. Also, another
subset is machined in the crystallized state that can cause significant machining damage affecting the
properties of the material.
The machining process can cause surface and subsurface damage that can decrease the flexural
strength of the material. Furthermore, damage can limit the minimum thickness of the material that
can be achieved with the machining process and affect the accuracy of the final part with respect to the
original designed dimensions.
This document provides guidance for evaluating the effects of machining on ceramic materials, the
dimensional changes occurring after crystallization and after sintering, and assessing machining
damage.
Specific qualitative and quantitative recommendations for freedom from biological hazard are not
included in this document, however when assessing possible biological or toxicological hazards,
reference should be made to ISO 10993-1 and ISO 7405. Basic material properties are not included in
this document, however when assessing material properties, reference should be made to ISO 6872.
v
© ISO 2022 – All rights reserved
---------------------- Page: 11 ----------------------
SIST EN ISO 18675:2023
---------------------- Page: 12 ----------------------
SIST EN ISO 18675:2023
INTERNATIONAL STANDARD ISO 18675:2022(E)
Dentistry — Machinable ceramic blanks
1 Scope
This document specifies test methods for machinable ceramic blanks used for the fabrication of dental
fixed restorations. This document also specifies the contents of the test report.
2 Normative references
The following documents are referred to in the text in such a way 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 6872, Dentistry — Ceramic materials
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1942, ISO 6872 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Materials
3.1.1
feldspathic ceramic
inorganic, non-metallic material which is predominantly a glassy material that consists of aluminum
silicates with either potassium, sodium or calcium
3.1.2
polymer infiltrated ceramic
dental ceramic which is an interconnected network of a ceramic and polymer formed by infiltration of a
porous ceramic network with a monomer
3.1.3
zirconia
ZrO
2
oxidized form of the metal zirconium (Zr), exhibiting three well-defined crystal structures (polymorphs
or phases) that can be monoclinic, tetragonal or cubic
3.1.4
glass ceramic
material manufactured by melting a glass, cooling it to the amorphous state, forming nuclei by controlled
heat treatment and then growing the nuclei into the crystalline phase(s) by a second controlled heat
treatment
1
© ISO 2022 – All rights reserved
---------------------- Page: 13 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
3.2 Properties
3.2.1
homogeneity
degree to which the density and properties are uniform throughout the entirety of the dental blank
3.2.2
shrinkage factor
volumetric or linear change in dimension during sintering of a green blank (3.3.1) or a partially sintered
blank (3.3.2) as labelled with a bar code or stated in the packaging
3.2.3
warpage
degree to which sections of the fully dense blank (3.3.3) or partially sintered blank (3.3.2) has a uniform
flat surface after final sintering to full density or post machining processing
3.2.4
machining damage
effect on surface and sub surface structure occurring during machining the blank to form the final part
or device
3.2.5
crystallization distortion
change in dimension of the machined part due to crystallization from a glass or a partially crystallized
glass ceramic to a fully crystallized glass ceramic
3.2.6
minimum machined thickness
minimum thickness that an intact part can be machined from a given blank of material
3.2.7
machinable ceramic blank
piece of material subjected to subtractive methods to remove material from the piece leaving the final
desired part
3.3 Types of blanks
3.3.1
green blank
blank in which powder has been pressed or cast to form the structure
3.3.2
partially sintered blank
blank which has been subjected to heating to cause partial sintering of the blank resulting in a blank
with improved mechanical properties but that is still porous and not fully dense
3.3.3
fully dense blank
blank which has been subjected to heating to cause full sintering of a ceramic powder to achieve full
density such as feldspathic, leucite and glass ceramic materials
3.4 Test piece
3.4.1
merlon
free standing wall of the test piece after the milling
2
© ISO 2022 – All rights reserved
---------------------- Page: 14 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
4 Homogeneity of partially sintered zirconia blanks
4.1 Classification
For the purposes of this document, machinable ceramic blanks shall be classified into the following
types:
— type 1: green blank (3.3.1);
— type 2: partially sintered blank (3.3.2);
— type 3: fully dense blank (3.3.3).
4.2 Determination of the shrinkage factor, d
4.2.1 Blanks characterized by one shrinkage factor for all three dimensions in space
4.2.1.1 Bar-size test specimen — Large zirconia blanks
Blanks of this type are discs and blocks that can be used to fabricate a wide variety of crown- and
bridgework, mostly covering multiple units up to full arches (if indicated by the manufacturer for the
provided zirconia material).
Mill five bar-size specimens with the following dimensions, w , b and l , out of the original blank (type
1 1 1
2) using the same thickness (e.g. 18 mm):
— width for specimen 1, w = (7,5 ± 2,5) mm;
1
— thickness for specimen 1, b = (7,5 ± 2,5) mm;
1
— length for specimen 1, l = (60 ± 10) mm.
1
Width and thickness can vary within the given limits. However, it is advised to manufacture specimen
with a square cross section to further improve the reproducibility of the measured shrinkage factor.
NOTE The specimen is positioned evenly within the blank geometry (avoid milling in extreme edge locations)
and does not include the surface of the blank.
Determine the exact dimensions (at least ±0,005 mm) of the milled partially sintered zirconia specimens
in all three directions in space by using a calibrated micrometre screw gauge or another appropriate
device accurate to at least ±0,005 mm. Repeat each measurement three times and calculate the average
value for all three directions in space respectively.
Afterwards sinter all five specimens according to the manufacturer’s instruction for use (including
recommendations for correct sintering support of the specimen).
Determine the dimensions of the fully sintered zirconia specimens in all three directions, width, w ,
2
thickness, b , and length, l , in space (at least ±0,005 mm) by using the calibrated micrometre screw
2 2
gauge or another appropriate device accurate to at least ±0,005 mm to yield the following values: w b
2, 2
and l .
2
Finally, calculate the resulting shrinkage factors, d, for all three directions in space with an accuracy of
at least at least 0,001 mm by using the following formulae:
— shrinkage factor width, d = w /w ;
w 1 2
— shrinkage factor thickness, d = b /b ;
b 1 2
— shrinkage factor length, d = l /l .
l 1 2
3
© ISO 2022 – All rights reserved
---------------------- Page: 15 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
Calculate the average shrinkage factor, d , for each bar-size specimen by using Formula (1) for specimen
av
1:
d = (d + d + d ) / 3 (1)
av1 w1 b1 l1
Calculate the final average shrinkage factor of the large zirconia blank by averaging the individual
results of all five test bars as given in Formula (2):
d = (d + d + d + d + d ) / 5 (2)
av av1 av2 av3 av4 av5
Compare d to the official value stated by the manufacturer for the given blank.
av
An example of a resulting shrinkage factor, d , is 1,229 5. Blanks of this type are blocks and can be used
av
to fabricate, for example, three-unit bridges (medium-size blanks) or single crowns (small-size blanks)
and are usually supplied in various (block-size) rectangular geometries.
Randomly choose five partially sintered zirconia blanks of the same lot of a given geometry, determine
the outer dimensions and sinter them to complete density.
Ensure that the provided energy of the sintering furnace which follows the originally supplied sintering
program by the manufacturer, ensures complete sintering and guarantees elimination of all porosities
within the examined blank. Details concerning the characterization of the used furnace shall be given
in the final report (see 4.4).
If it is uncertain that the large zirconia block can be sintered to full density in the available furnace then
fabricate smaller specimens (with the dimensions as defined in this subclause) and sinter those five
specimens (one specimen per zirconia blank, five blanks overall) to complete the density by using the
sintering program as provided by the manufacturer. Always apply appropriate sintering support of the
specimen according to the manufacturer’s recommendation.
If the characterized zirconia blank does not allow the fabrication of test specimen with the dimensions,
w , b and l , (because the outer dimensions of the blank are too small), the manufacturer may modify
1 1 1
the dimensions of the test specimen as follows:
— w = (7,5 ± 2,5) mm;
1
— b = (7,5 ± 2,5) mm;
1
— l ≥ 2 × w (or ≥ 2 × b , whichever is larger).
1 1 1
Width and thickness may vary within the given limits. However, it is advised to manufacture the
specimen with a square cross section to further improve the reproducibility of the measured shrinkage
factor.
The dimensions of these individual test specimens shall be reported (before and after sintering, see
4.4).
Finally, calculate the resulting five shrinkage factors with an accuracy of at least ±0,005 mm following
the routine and formulae and compare to the values stated by the manufacturer for those five individual
zirconia blanks.
4.2.1.2 Cubic test specimen
Mill five cubic specimens each with the dimension 10 mm × 10 mm × 10 mm out of the originally
partially sintered blank using a common thickness (e.g. 18 mm).
Determine the exact dimensions (at least ±0,005 mm) of the milled partially sintered zirconia specimens
in all three directions in space by using a calibrated micrometer screw gauge or another appropriate
device accurate to at least ±0,005 mm. Repeat each measurement three times and calculate the average
value for all three directions in space respectively.
4
© ISO 2022 – All rights reserved
---------------------- Page: 16 ----------------------
SIST EN ISO 18675:2023
ISO 18675:2022(E)
Afterwards, sinter all five specimens to complete the density according to the sintering program
provided by the manufacturer in the official instruction for use (including recommendations for
correct sintering support of the specimen). If necessary, adjust the sintering program slightly to ensure
complete elimination of any residual porosity.
Determine the volume before sintering (v ) and after sintering (v ) for each individual cube.
BS AS
The shrinkage factor for each specimen (d ) is the volume before sintering determined as given in
V
Formula (3) (here, it is given for cube 1):
1/3
d = (v / v ) (3)
V1 BS1 AS1
where
d is the shrinkage factor for specimen 1;
V1
v is the volume before sintering for specimen 1;
...
SLOVENSKI STANDARD
oSIST prEN ISO 18675:2022
01-oktober-2022
Zobozdravstvo - Keramični polizdelki, ki jih je mogoče obdelovati (ISO 18675:2022)
Dentistry - Machinable ceramic blanks (ISO 18675:2022)
Zahnheilkunde - Maschinierbare Keramikblanks (ISO 18675:2022)
Médecine bucco-dentaire - Ébauches en céramique usinables (ISO 18675:2022)
Ta slovenski standard je istoveten z: prEN ISO 18675
ICS:
11.060.10 Zobotehnični materiali Dental materials
oSIST prEN ISO 18675:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 18675:2022
---------------------- Page: 2 ----------------------
oSIST prEN ISO 18675:2022
INTERNATIONAL ISO
STANDARD 18675
First edition
2022-05
Dentistry — Machinable ceramic
blanks
Médecine bucco-dentaire — Ébauches en céramique usinables
Reference number
ISO 18675:2022(E)
© ISO 2022
---------------------- Page: 3 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized 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 ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
© ISO 2022 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
3.1 Materials . 1
3.2 Properties . 2
3.3 Types of blanks . 2
3.4 Test piece . 2
4 Homogeneity of partially sintered zirconia blanks. 3
4.1 Classification . 3
4.2 Determination of the shrinkage factor, d . 3
4.2.1 Blanks characterized by one shrinkage factor for all three dimensions in
space . 3
4.2.2 Blanks characterized by two or three shrinkage factors . 5
4.3 Recommendations . 6
4.4 Test report . 6
5 Warpage . 7
5.1 Test method . 7
5.1.1 Large zirconia blanks . 7
5.1.2 Medium- and small-size zirconia blanks . 8
5.2 Recommendations . 8
5.3 Test report . 9
6 Dimensional stability post machining crystallization of glass ceramics .9
6.1 General . 9
6.2 Test method . 9
6.2.1 Sample preparation . 9
6.2.2 Characterization before heat treatment . 10
6.2.3 Heat treatment . 11
6.2.4 Characterization after heat treatment . 11
6.3 Test report .12
7 Machining damage .13
7.1 General .13
7.2 Test methods . 13
7.3 Test report .13
8 Machinability using the merlon fracture test .14
8.1 General . 14
8.2 Test method . 15
8.2.1 Dimensions of test geometries . 15
8.2.2 Machining . 16
8.2.3 Characterization of milled specimen . 16
8.3 Recommendations . 17
8.4 Test report . 17
Bibliography .19
iii
© ISO 2022 – All rights reserved
---------------------- Page: 5 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(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 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, 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 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 the 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 received (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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 9, Dental
CAD/CAM systems, in collaboration with the European Committee for Standardization (CEN) Technical
Committee CEN/TC 55, Dentistry, in accordance with the Agreement on technical cooperation between
ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
© ISO 2022 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
Introduction
A variety of ceramic blank materials are being used in machining systems for fabrication of various
restorations. Although all these materials can have different chemical and microstructural makeup,
there are some unique and common concerns for machining and performance of these materials.
Machining damage, minimum machined thickness, and machining tolerances all are common concerns
for these materials.
The overwhelming use of zirconia and alumina is in the form of green or partially sintered blanks with
shrinkage values of 20 % to 35 % by volume when sintered to full density. In order for the restoration
to be fabricated with proper accuracy, the blank density should be carefully measured and conveyed
to the computer controlled milling unit. This allows for proper oversizing and shrinkage to provide
an accurate fit. Furthermore, the blank should be homogeneous throughout the body, otherwise
differential shrinkage occurs resulting in significant warping and departure from linearity.
With respect to glass ceramics, a subset requires crystallization post-machining during which distortion
can occur placing the machined part out of the tolerance specified for the restoration. Also, another
subset is machined in the crystallized state that can cause significant machining damage affecting the
properties of the material.
The machining process can cause surface and subsurface damage that can decrease the flexural
strength of the material. Furthermore, damage can limit the minimum thickness of the material that
can be achieved with the machining process and affect the accuracy of the final part with respect to the
original designed dimensions.
This document provides guidance for evaluating the effects of machining on ceramic materials, the
dimensional changes occurring after crystallization and after sintering, and assessing machining
damage.
Specific qualitative and quantitative recommendations for freedom from biological hazard are not
included in this document, however when assessing possible biological or toxicological hazards,
reference should be made to ISO 10993-1 and ISO 7405. Basic material properties are not included in
this document, however when assessing material properties, reference should be made to ISO 6872.
v
© ISO 2022 – All rights reserved
---------------------- Page: 7 ----------------------
oSIST prEN ISO 18675:2022
---------------------- Page: 8 ----------------------
oSIST prEN ISO 18675:2022
INTERNATIONAL STANDARD ISO 18675:2022(E)
Dentistry — Machinable ceramic blanks
1 Scope
This document specifies test methods for machinable ceramic blanks used for the fabrication of dental
fixed restorations. This document also specifies the contents of the test report.
2 Normative references
The following documents are referred to in the text in such a way 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 6872, Dentistry — Ceramic materials
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1942, ISO 6872 and the
following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Materials
3.1.1
feldspathic ceramic
inorganic, non-metallic material which is predominantly a glassy material that consists of aluminum
silicates with either potassium, sodium or calcium
3.1.2
polymer infiltrated ceramic
dental ceramic which is an interconnected network of a ceramic and polymer formed by infiltration of a
porous ceramic network with a monomer
3.1.3
zirconia
ZrO
2
oxidized form of the metal zirconium (Zr), exhibiting three well-defined crystal structures (polymorphs
or phases) that can be monoclinic, tetragonal or cubic
3.1.4
glass ceramic
material manufactured by melting a glass, cooling it to the amorphous state, forming nuclei by controlled
heat treatment and then growing the nuclei into the crystalline phase(s) by a second controlled heat
treatment
1
© ISO 2022 – All rights reserved
---------------------- Page: 9 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
3.2 Properties
3.2.1
homogeneity
degree to which the density and properties are uniform throughout the entirety of the dental blank
3.2.2
shrinkage factor
volumetric or linear change in dimension during sintering of a green blank (3.3.1) or a partially sintered
blank (3.3.2) as labelled with a bar code or stated in the packaging
3.2.3
warpage
degree to which sections of the fully dense blank (3.3.3) or partially sintered blank (3.3.2) has a uniform
flat surface after final sintering to full density or post machining processing
3.2.4
machining damage
effect on surface and sub surface structure occurring during machining the blank to form the final part
or device
3.2.5
crystallization distortion
change in dimension of the machined part due to crystallization from a glass or a partially crystallized
glass ceramic to a fully crystallized glass ceramic
3.2.6
minimum machined thickness
minimum thickness that an intact part can be machined from a given blank of material
3.2.7
machinable ceramic blank
piece of material subjected to subtractive methods to remove material from the piece leaving the final
desired part
3.3 Types of blanks
3.3.1
green blank
blank in which powder has been pressed or cast to form the structure
3.3.2
partially sintered blank
blank which has been subjected to heating to cause partial sintering of the blank resulting in a blank
with improved mechanical properties but that is still porous and not fully dense
3.3.3
fully dense blank
blank which has been subjected to heating to cause full sintering of a ceramic powder to achieve full
density such as feldspathic, leucite and glass ceramic materials
3.4 Test piece
3.4.1
merlon
free standing wall of the test piece after the milling
2
© ISO 2022 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
4 Homogeneity of partially sintered zirconia blanks
4.1 Classification
For the purposes of this document, machinable ceramic blanks shall be classified into the following
types:
— type 1: green blank (3.3.1);
— type 2: partially sintered blank (3.3.2);
— type 3: fully dense blank (3.3.3).
4.2 Determination of the shrinkage factor, d
4.2.1 Blanks characterized by one shrinkage factor for all three dimensions in space
4.2.1.1 Bar-size test specimen — Large zirconia blanks
Blanks of this type are discs and blocks that can be used to fabricate a wide variety of crown- and
bridgework, mostly covering multiple units up to full arches (if indicated by the manufacturer for the
provided zirconia material).
Mill five bar-size specimens with the following dimensions, w , b and l , out of the original blank (type
1 1 1
2) using the same thickness (e.g. 18 mm):
— width for specimen 1, w = (7,5 ± 2,5) mm;
1
— thickness for specimen 1, b = (7,5 ± 2,5) mm;
1
— length for specimen 1, l = (60 ± 10) mm.
1
Width and thickness can vary within the given limits. However, it is advised to manufacture specimen
with a square cross section to further improve the reproducibility of the measured shrinkage factor.
NOTE The specimen is positioned evenly within the blank geometry (avoid milling in extreme edge locations)
and does not include the surface of the blank.
Determine the exact dimensions (at least ±0,005 mm) of the milled partially sintered zirconia specimens
in all three directions in space by using a calibrated micrometre screw gauge or another appropriate
device accurate to at least ±0,005 mm. Repeat each measurement three times and calculate the average
value for all three directions in space respectively.
Afterwards sinter all five specimens according to the manufacturer’s instruction for use (including
recommendations for correct sintering support of the specimen).
Determine the dimensions of the fully sintered zirconia specimens in all three directions, width, w ,
2
thickness, b , and length, l , in space (at least ±0,005 mm) by using the calibrated micrometre screw
2 2
gauge or another appropriate device accurate to at least ±0,005 mm to yield the following values: w b
2, 2
and l .
2
Finally, calculate the resulting shrinkage factors, d, for all three directions in space with an accuracy of
at least at least 0,001 mm by using the following formulae:
— shrinkage factor width, d = w /w ;
w 1 2
— shrinkage factor thickness, d = b /b ;
b 1 2
— shrinkage factor length, d = l /l .
l 1 2
3
© ISO 2022 – All rights reserved
---------------------- Page: 11 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
Calculate the average shrinkage factor, d , for each bar-size specimen by using Formula (1) for specimen
av
1:
d = (d + d + d ) / 3 (1)
av1 w1 b1 l1
Calculate the final average shrinkage factor of the large zirconia blank by averaging the individual
results of all five test bars as given in Formula (2):
d = (d + d + d + d + d ) / 5 (2)
av av1 av2 av3 av4 av5
Compare d to the official value stated by the manufacturer for the given blank.
av
An example of a resulting shrinkage factor, d , is 1,229 5. Blanks of this type are blocks and can be used
av
to fabricate, for example, three-unit bridges (medium-size blanks) or single crowns (small-size blanks)
and are usually supplied in various (block-size) rectangular geometries.
Randomly choose five partially sintered zirconia blanks of the same lot of a given geometry, determine
the outer dimensions and sinter them to complete density.
Ensure that the provided energy of the sintering furnace which follows the originally supplied sintering
program by the manufacturer, ensures complete sintering and guarantees elimination of all porosities
within the examined blank. Details concerning the characterization of the used furnace shall be given
in the final report (see 4.4).
If it is uncertain that the large zirconia block can be sintered to full density in the available furnace then
fabricate smaller specimens (with the dimensions as defined in this subclause) and sinter those five
specimens (one specimen per zirconia blank, five blanks overall) to complete the density by using the
sintering program as provided by the manufacturer. Always apply appropriate sintering support of the
specimen according to the manufacturer’s recommendation.
If the characterized zirconia blank does not allow the fabrication of test specimen with the dimensions,
w , b and l , (because the outer dimensions of the blank are too small), the manufacturer may modify
1 1 1
the dimensions of the test specimen as follows:
— w = (7,5 ± 2,5) mm;
1
— b = (7,5 ± 2,5) mm;
1
— l ≥ 2 × w (or ≥ 2 × b , whichever is larger).
1 1 1
Width and thickness may vary within the given limits. However, it is advised to manufacture the
specimen with a square cross section to further improve the reproducibility of the measured shrinkage
factor.
The dimensions of these individual test specimens shall be reported (before and after sintering, see
4.4).
Finally, calculate the resulting five shrinkage factors with an accuracy of at least ±0,005 mm following
the routine and formulae and compare to the values stated by the manufacturer for those five individual
zirconia blanks.
4.2.1.2 Cubic test specimen
Mill five cubic specimens each with the dimension 10 mm × 10 mm × 10 mm out of the originally
partially sintered blank using a common thickness (e.g. 18 mm).
Determine the exact dimensions (at least ±0,005 mm) of the milled partially sintered zirconia specimens
in all three directions in space by using a calibrated micrometer screw gauge or another appropriate
device accurate to at least ±0,005 mm. Repeat each measurement three times and calculate the average
value for all three directions in space respectively.
4
© ISO 2022 – All rights reserved
---------------------- Page: 12 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
Afterwards, sinter all five specimens to complete the density according to the sintering program
provided by the manufacturer in the official instruction for use (including recommendations for
correct sintering support of the specimen). If necessary, adjust the sintering program slightly to ensure
complete elimination of any residual porosity.
Determine the volume before sintering (v ) and after sintering (v ) for each individual cube.
BS AS
The shrinkage factor for each specimen (d ) is the volume before sintering determined as given in
V
Formula (3) (here, it is given for cube 1):
1/3
d = (v / v ) (3)
V1 BS1 AS1
where
d is the shrinkage factor for specimen 1;
V1
v is the volume before sintering for specimen 1;
BS1
v is the volume after sintering for specimen 1.
AS1
Calculate the resulting five individual shrinkage-factors of the cubes with an accuracy of at least
±0,005 mm.
Calculate the final average shrinkage factor of the large zirconia blank by averaging the individual
results of all five test cubes as given in Formula (4):
d = (d + d + d + d + d ) / 5 (4)
V V1 V2 V3 V4 V5
Compare d to the official value stated by the manufacturer for the given blank. An example of a
v
resulting shrinkage factor d is, for example, 1,229 5.
V
4.2.1.3 Medium and small-size zirconia blanks
Prepare specimens by sectioning five randomly selected blanks into cubes 10 mm × 10 mm × 10 mm.
Mark each cube for the x, y and z sides. Determine the exact dimensions (at least ±0,005 mm) of the
milled partially sintered zirconia specimens in all three directions in space by using a calibrated
micrometre screw gauge or another appropriate device accurate to at least ±0,005 mm. Repeat each
measurement three times and calculate the average value for all three directions in space respectively.
Afterwards, sinter all five specimens to complete density according to the sintering program provided
by the manufacturer in the official instruction for use (including recommendations for correct sintering
support of the specimen). If necessary, adjust the sintering program slightly to ensure complete
elimination of any residual porosity.
Determine the volume before sintering (v ) and after sintering (v ). The shrinkage factor (d ) is
BS AS V
determined as given in Formula (5) for each cube:
1/3
d = (v /v ) (5)
V BS AS
Calculate the resulting five shrinkage factors with an accuracy of at least ±0,005 mm and compare to
the values stated by the manufacturer for those five individual zirconia blanks.
4.2.2 Blanks characterized by two or three shrinkage factors
For discs, when shrinkage factors are indicated by the manufacturer for x, y, and z direction, the
shrinkage factor shall be measured in each direction (bar-size specimen) or 4.2.1.2 (cubic specimen). It
shall be ensured, that the x-y-z direction of the milled test specimen correctly reflects the x-y-z direction
defined by the manufacturer.
5
© ISO 2022 – All rights reserved
---------------------- Page: 13 ----------------------
oSIST prEN ISO 18675:2022
ISO 18675:2022(E)
For each of the five specimens milled per large blank, the following individual shrinkage factors per
specimen, d , d and d , result [here, it is given for specimen 1, length determined before sintering
x1 y1 z1
(BS) and after sintering (AS)]:
— d shrinkage factor x direction specimen 1, x /x ;
x1 1BS 1AS
— d shrinkage factor y direction specimen 1, y /y ;
y1 1BS 1AS
— d shrinkage factor z direction specimen 1, z /z .
z1 1BS 1AS
Calculate the resulting average shrinkage factor in x, y and z directions with an accuracy of at least
±0,005 mm by averaging all five specimens and applying Formula (6) (here, it is given for x direction):
d = (d + d + d + d + d ) / 5 (6)
x x1 x2 x3 x4 x15
Compare d d and d to the official value stated by the manufacturer for the given blank.
x, y z
For blocks, when shrinkage factors are indicated by the manufacturer for x, y, and z directions, the
shrinkage factor shall be measured in each direction by applying a rectangular geometry (as described
in 4.2.1.1) or a cubic test geometry (see 4.2.1.2).
For each of the five individual specimens (that are independent of each other), the following shrinkage
factors, d , d and d , result [here, it is given for specimen 1, length determined before sintering (BS)
x1 y1 z1
and after sintering (AS)]:
— d shrinkage factor x direction specimen 1, x /x ;
x1 1BS 1AS
— d shrinkage factor y direction specimen 1, y /y ;
y1 1BS 1AS
— d shrinkage factor z direction specimen 1, z /z
z1 1BS 1AS.
Calculate the resulting shrinkage factors in x, y and z directions for each speci
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.