prEN ISO 13356

• Abstract:

  This document specifies the requirements and corresponding test methods for a biocompatible and bio-inert ceramic bone-substitute material based on yttriastabilized tetragonal zirconia (yttria tetragonal zirconia polycrystal, Y-TZP) for use as a material for surgical implants.

• Status: Not Published
• Publication Date: 14-Feb-2028
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: CEN/TC 55 - Dentistry
• Drafting Committee: CEN/TC 55 - Dentistry
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 27-Aug-2026
• Completion Date: 27-Aug-2026
• Ref Project: oSIST prEN ISO 13356:2026 - Implants for surgery - Alumina ceramic material: Zirconia - Yttria-stabilized tetragonal zirconia (Y-TZP) (ISO/DIS 13356:2026)

• Revises: EN ISO 13356:2015 - Implants for surgery - Ceramic materials based on yttria-stabilized tetragonal zirconia (Y-TZP) (ISO 13356:2015)
• Effective Date: 13-May-2026

prEN ISO 13356 is a CEN draft aligned with ISO/DIS 13356:2026 for yttria-stabilized tetragonal zirconia (Y-TZP) used as a ceramic bone-substitute material in surgical implants. It specifies the material requirements and test methods for manufacturers, test laboratories, and quality teams that need to verify raw implant material rather than the finished medical device.

What does prEN ISO 13356 specify?

prEN ISO 13356 specifies the requirements and test methods for a biocompatible, bio-inert ceramic bone-substitute material based on yttria-stabilized tetragonal zirconia (Y-TZP) for surgical implant use. The document is organized into scope, normative references, terms and definitions, test categories, specimen preparation, test methods, and an informative annex on radioactivity testing.

Clause 4 separates the work into production-control tests and broader specification tests. Clause 6 then gives the methods for density, chemistry, microstructure, strength, stiffness, fatigue, radioactivity, and accelerated aging.

Annex	What it covers
Annex A	Informative gamma-spectrometry method for testing radioactivity

What are the key requirements of prEN ISO 13356?

prEN ISO 13356 sets both routine control tests and additional tests for demonstrating conformance to the material specification. The main practical point is that the standard treats Y-TZP as a controlled raw material, so the test pieces must represent the production route used for implant components.

Test categories and property limits

Clause 4.1 divides the required tests into two categories. Category 1 covers bulk density, chemical composition, microstructure, strength including Weibull modulus, and accelerated aging for monoclinic fraction. Category 2 adds hardness, Young’s modulus, fatigue strength, accelerated aging for strength, quantity of monoclinic phase, and radioactivity.

Clause 4.2 and Table 1 tie those tests to acceptance limits. In practice, that means the measured batch has to meet the required density, composition balance, grain size, phase stability, strength, stiffness, hardness, fatigue resistance, and radioactivity limits before it can be treated as conforming material.

Test specimen preparation

Clause 5 requires test specimens to be prepared using the same production methods as regular implant components, including the precursor powder, pressing technique, pressure, and firing conditions, unless the manufacturer justifies another approach. This matters because zirconia properties are sensitive to processing, so results from specially prepared specimens would not reflect real production material.

Physical and chemical characterization

Clause 6.1 requires bulk density to be reported in accordance with EN ISO 18754. Clause 6.2 allows chemical composition to be determined by ICP-OES, X-ray fluorescence, or atomic absorption methods. In practice, these tests check whether the batch chemistry matches the intended zirconia-based composition and whether contaminants stay within the required limits.

Clause 6.3 controls microstructure through grain size measurement by the linear intercept method on multiple micrographs. The report must identify the material batch, describe specimen preparation, include at least one micrograph, and reference the standard. Clause 6.3.3 also requires X-ray diffraction measurement of the monoclinic phase on polished surfaces, which is important because the tetragonal-to-monoclinic transformation affects long-term stability.

Mechanical performance

Clause 6.5 uses biaxial flexural strength as one main strength route, and Clause 6.6 allows four-point bending strength as the alternative route. Clause 6.7 then applies Weibull statistics to the strength data, using at least 30 specimens. For a reader, this means the standard is not only checking average strength but also how scattered the results are from batch to batch.

Clause 6.8 covers Young’s modulus, and Clause 6.9 covers hardness by the Vickers method with a 9,81 N load. These tests help confirm that the material is sufficiently stiff and resistant to indentation for implant use.

Fatigue, aging, and radioactivity

Clause 6.10 defines cyclic fatigue in four-point bending under simulated physiological conditions, with saline at 37 °C and cycling up to one million cycles. This is the test that checks whether the material can survive repeated loading rather than only single fracture events.

Clause 6.12 uses steam aging at 134 °C and 0,2 MPa for 5 h, then rechecks monoclinic phase content and strength. Clause 6.11 says radioactivity should be rechecked when the zirconia feedstock comes from a different origin or refining process. In practice, these clauses are aimed at phase stability and traceability of the starting powder.

What terms does prEN ISO 13356 define?

prEN ISO 13356 uses a small set of technical terms and abbreviations that are central to the test program.

• Y-TZP - yttria-stabilized tetragonal zirconia polycrystal, the zirconia ceramic material covered by the standard.
• ICP-OES - Inductively Coupled Plasma - Optical Emission Spectrometry, one of the methods allowed for chemical composition.
• XRF - X-ray fluorescence, another allowed method for chemical analysis of the material.
• Weibull modulus - a statistical measure used to describe the scatter in strength data from ceramic test specimens.
• Monoclinic phase - the zirconia phase measured to assess transformation and aging behavior.
• HPGe - high-purity germanium detector, the detector used in the radioactivity test method in Annex A.
• MCA - multichannel analyser, the instrument that processes the gamma-spectrometry signal in Annex A.

Who uses prEN ISO 13356?

prEN ISO 13356 is used by manufacturers of zirconia implant raw material, especially those making ceramic bone-substitute material for surgical implants. It is also used by quality control teams, test laboratories, and material engineers who need to release batches, compare production lots, or validate processing routes.

Procurement and buyer teams can use it to specify what evidence they need from suppliers. Regulatory and conformity-assessment personnel can use it to check whether the material testing package is based on the same methods and specimen conditions as the standard.

What changed in prEN ISO 13356 from the previous edition?

prEN ISO 13356 cancels and replaces ISO 13356:2015. The foreword states that this fourth edition was technically revised.

The changes named in the document are:

• the title was changed
• normative references were updated
• the requirements and normative references in Table 1 were revised
• the number of test specimens for each test item was reviewed
• the equation for calculating monoclinic phase was corrected
• radioactivity testing was moved to an informative annex

Which standards are used with prEN ISO 13356?

prEN ISO 13356 relies on several referenced standards for measurement methods, apparatus calibration, and statistical evaluation.

Referenced standard	What it contributes
ISO 3611	Micrometers for external measurements used in specimen dimensional checks
ISO 7500-1	Calibration and verification of the force-measuring system of testing machines
ISO 14704	Flexural strength of monolithic ceramics and the 4-point bending test setup
ISO 17561	Young’s modulus of monolithic ceramics by sonic resonance
ISO 22214	Cyclic bending fatigue test method for monolithic ceramics
EN 843-2	Mechanical property method for Young’s modulus, shear modulus, and Poisson’s ratio
EN ISO 13383-1	Microstructural characterization and grain size determination
EN ISO 14705	Vickers hardness test method for monolithic ceramics
EN ISO 18754	Density and apparent porosity determination
EN ISO 20501	Weibull statistics for strength data
EN ISO 12677	X-ray fluorescence chemical analysis of refractory products, used as one chemistry method in Clause 6.2
ASTM C1259	Dynamic Young’s modulus, shear modulus, and Poisson’s ratio by impulse excitation
ASTM C1327	Vickers indentation hardness of advanced ceramics
ASTM C1499-19	Monotonic equibiaxial flexural strength at ambient temperature
ASTM C1198	Dynamic Young’s modulus, shear modulus, and Poisson’s ratio by sonic resonance
ASTM C1239-26	Reporting uniaxial strength data and estimating Weibull parameters
ASTM C1331	Ultrasonic velocity in advanced ceramics
ASTM E112-13	Average grain size determination

What does the prEN ISO 13356 document contain?

prEN ISO 13356 contains the test framework, the specimen-preparation rules, the apparatus and procedures for density, chemistry, microstructure, strength, stiffness, hardness, cyclic fatigue, radioactivity, and accelerated aging, and the reporting details for several tests. It also includes Table 1 with the material-property limits, Figure 1 with the biaxial flexure test arrangement, and formulas for monoclinic phase, fracture stress, and cyclic fatigue loading.

Annex A gives a radioactivity test based on gamma spectrometry, including apparatus, sample preparation, energy calibration, efficiency calibration, sample analysis, and reporting. The document is therefore a practical test specification for laboratory verification, batch control, and material qualification of Y-TZP implant ceramic.

SLOVENSKI STANDARD
01-oktober-2026
Vsadki (implantati) za kirurgijo - Aluminijev keramični material: Cirkonij -
Tetragonalni cirkonij, stabiliziran z itrijem (Y-TZP) (ISO/DIS 13356:2026)
Implants for surgery - Alumina ceramic material: Zirconia - Yttria-stabilized tetragonal
zirconia (Y-TZP) (ISO/DIS 13356:2026)
Chirurgische Implantate - Keramische Werkstoffe: Zirconia - Yttrium-stabilisiertes
tetragonales Zirkoniumoxid (Y‑TZP) (ISO/DIS 13356:2026)
Implants chirurgicaux - Produits céramiques à base de zircone tétragonal stabilisée à
l'yttrium (Y-TZP) (ISO/DIS 13356:2026)
Ta slovenski standard je istoveten z: prEN ISO 13356
ICS:
11.040.40 Implantanti za kirurgijo, Implants for surgery,
protetiko in ortetiko prosthetics and orthotics
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 13356
ISO/TC 150/SC 1
Implants for surgery — Alumina
Secretariat: DIN
ceramic material: Zirconia — Yttria-
Voting begins on:
stabilized tetragonal zirconia
2026-08-26
(Y-TZP)
Voting terminates on:
ICS: 11.040.40
2026-11-18
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 13356:2026(en)
DRAFT
ISO/DIS 13356:2026(en)
International
Standard
ISO/DIS 13356
ISO/TC 150/SC 1
Implants for surgery — Alumina
Secretariat: DIN
ceramic material: Zirconia — Yttria-
Voting begins on:
stabilized tetragonal zirconia
(Y-TZP)
Voting terminates on:
ICS:
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document has not been edited by the ISO Central Secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 13356:2026(en)
ii
ISO/DIS 13356:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Test categories . 2
4.1 General .2
4.1.1 Category 1 .2
4.1.2 Category 2 .2
4.2 Physical and chemical properties .2
5 Preparation of Test specimens . 4
6 Test Methods . 4
6.1 Bulk density .4
6.2 Chemical composition .4
6.3 Microstructure .4
6.3.1 Principle .4
6.3.2 Test report .5
6.3.3 Amount of monoclinic phase .5
6.5 Biaxial flexural strength.6
6.5.1 Principle .6
6.5.2 Apparatus .6
6.5.3 Preparation of test specimens .6
6.5.4 Procedure .7
6.5.5 Calculation of results .8
6.5.6 Test report .8
6.6 Four-point bending strength.8
6.7 Weibull modulus .9
6.8 Young’s modulus.9
6.9 Hardness .9
6.10 Cyclic fatigue .9
6.10.1 Principle .9
6.10.2 Apparatus .9
6.10.3 Sample size and preparation of test specimens .9
6.10.4 Procedure and sample requirement .9
6.10.5 Test Report.10
6.11 Radioactivity .10
6.12 Accelerated aging test .10
6.12.1 General .10
6.12.2 Procedure .10
6.12.3 Evaluation of accelerated aging outcome .10
Annex A (informative) Testing for radioactivity .11
Bibliography .13

iii
ISO/DIS 13356:2026(en)
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 150, Implants for surgery, Subcommittee SC 1,
Materials.
This forth edition cancels and replaces the third edition (ISO 13356:2015), which has been technically
revised.
— title changed to Implants for surgery —Alumina ceramic material:Zirconia — Yttria-stabilized tetragonal
zirconia (Y-TZP);
— normative references were updated;
— requirements and normative references in Table 1 were revised;
— the numbers of test specimens for each test item were reviewed;
— the equation for calculating the amount of monoclinic phase was corrected ;
— Testing for radioacitity was moved to an informative annex.
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/DIS 13356:2026(en)
Introduction
While no known surgical implant material has ever been shown to cause absolutely no adverse reactions
in the human body, long-term clinical experience with the material referred to in this document has shown
that an acceptable level of biological response can be expected when the material is used in appropriate
applications. However, this standard covers the raw material and not finished medical devices, where the
design and fabrication of the device can impact biological response.

v
DRAFT International Standard ISO/DIS 13356:2026(en)
Implants for surgery — Alumina ceramic material: Zirconia —
Yttria-stabilized tetragonal zirconia (Y-TZP)
1 Scope
This document specifies the requirements and corresponding test methods for bio-inert ceramic bone-
substitute material based on yttria-stabilized tetragonal zirconia (yttria tetragonal zirconia polycrystal,
Y-TZP) for use as a material for surgical implants.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment — Design and
metrological characteristics of micrometers for external measurements
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 14704, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for flexural strength
of monolithic ceramics at room temperature
ISO 17561, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for elastic moduli of
monolithic ceramics at room temperature by sonic resonance
ISO 22214, Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for cyclic bending
fatigue of monolithic ceramics at room temperature
EN 843-2, Advanced technical ceramics - Mechanical properties of monolithic ceramics at room temperature -
Part 2: Determination of Young's modulus, shear modulus and Poisson's ratio
EN ISO 13383-1, Fine ceramics (advanced ceramics, advanced technical ceramics) - Microstructural
characterization - Part 1: Determination of grain size and size distribution (ISO 13383-1:2012)
EN ISO 14705, Fine ceramics (advanced ceramics, advanced technical ceramics) - Test method for hardness of
monolithic ceramics at room temperature (ISO 14705:2016)
EN ISO 18754, Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of density and
apparent porosity (ISO 18754:2020)
EN ISO 20501, Fine ceramics (advanced ceramics, advanced technical ceramics) - Weibull statistics for strength
data (ISO 20501:2019)
ASTM C 1259, Standard Test Method For Dynamic Young's Modulus, Shear Modulus, And Poisson's Ratio For
Advanced Ceramics By Impulse Excitation Of Vibration
ASTM C 1327, Standard Test Method For Vickers Indentation Hardness Of Advanced Ceramics
ASTM C 1499-19, Standard Test Method For Monotonic Equibiaxial Flexural Strength Of Advanced Ceramics At
Ambient Temperature
ASTM C1198, Standard Test Method For Dynamic Young’S Modulus, Shear Modulus, And
Poisson’S Ratio For Advanced Ceramics By Sonic Resonance

ISO/DIS 13356:2026(en)
ASTM C1239-26, Standard Practice For Reporting Uniaxial Strength Data And Estimating Weibull Distribution
Parameters For Advanced Ceramics
ASTM C1331, Standard Practice For Measuring Ultrasonic Velocity In Advanced Ceramics With Broadband
Pulse-Echo Cross-Correlation Method
ASTM E112-13, Standard Test Methods For Determining Average Grain Size
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Test categories
4.1 General
The required tests are divided into two categories.
4.1.1 Category 1
The following test shall be performed for periodical production control:
a) bulk density;
b) chemical composition;
c) microstructure;
d) strength (including Weibull modulus);
e) accelerated aging (monoclinic fraction).
4.1.2 Category 2
The manufacturer shall define the general materials specification. In addition to all tests in 4.1.1, the
following tests shall be performed to demonstrate compliance with the material specification:
a) hardness;
b) Young’s modulus;
c) fatigue strength;
d) accelerated aging (strength);
e) quantity of monoclinic phase;
f) radioactivity.
4.2 Physical and chemical properties
The physical and chemical properties, when tested as specified in Clause 6, shall comply with the values
specified in Table 1.
ISO/DIS 13356:2026(en)
Table 1 — Limits for material properties
Test
Property Unit Requirement Reference Subclause
category
Bulk density g/cm 1 ≥ 6,00 ISO 18754 6.2
Chemical composition 6.3
ZrO +HfO +Y O ≥ 99,0
2 2 2 3
Y O > 4,5 to ≤ 6,0
2 3
% mass
HfO 1 ≤ 5
fraction
Al O ≤ 0,5
2 3
Other oxides ≤ 0,5
Microstructure 6.5
Grain size Intercept distance ≤ 0,4
ISO 13383-1
μm 1
ASTM E112
Standard deviation < 0,2
Amount of monoclinic See 6.5.3
% molar
phase
2 ≤ 20
fraction
Strength: alternative of 1) or 2)
a
1a) Biaxial flexure 1 ≥ 500 ASTM C1499 6.6
1b) Weibull modulus ISO 20501
1 ≥ 8 6.8
ASTM C1239
2a) 4-point bending ISO 14704
MPa
1 ≥ 800 EN 843–1 6.7
ASTM C1161
2b) Weibull modulus ISO 20501
1 ≥ 8 6.8
ASTM C 1239
Young's modulus ISO 17561
EN 843–2
GPa 2 ≥ 200 6.9
ASTM C1198
ASTM C1259
ASTM C1331
Hardness ISO 14705
GPa 2 ≥ 11,8 6.10
ASTM C1327
Cyclic fatigue limit stress
MPa 2 ≥ 320 ISO 22214 6.11
at 106 cycles
a
Radioactivity
Bq/kg 2 ≤ 200 — 6.12
Annex A
Accelerated aging 6.12
a
The radioactivity, defined as the sum of the mass activity of U238, Ra226, Th232, and determined by gamma spectroscopy
on the ready-to-use powder should be equal or less than 200 Bq/kg. This value will be reviewed at the next revision of this
Internation
...