ISO 23317:2014

INTERNATIONAL ISO
STANDARD 23317
Third edition
2014-06-15
Implants for surgery — In vitro
evaluation for apatite-forming ability
of implant materials
Implants chirurgicaux — Évaluation in vitro de la capacité de
formation d’apatite des matériaux d’implants
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
5 Test specimen . 2
5.1 Specimen configuration and size . 2
5.2 Specimen preparation . 2
6 Simulated body fluid . 3
6.1 General . 3
6.2 Reagents for SBF . 3
6.3 Preparation of SBF . 4
6.4 Confirmation of ion concentration of SBF . 6
6.5 Preservation of SBF . 6
7 Procedure. 6
8 Test report . 8
Annex A (informative) Apparatus for preparing SBF . 9
Annex B (informative) Preparation of standard glasses for evaluating apatite-forming ability .10
Bibliography .12
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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The committee responsible for this document is ISO/TC 150, Implants for surgery, Subcommittee SC 1,
Materials.
This third edition cancels and replaces the second edition (ISO 23317:2012), which has been editorially
revised.
iv © ISO 2014 – All rights reserved

Introduction
It has been revealed that materials of various kinds bond to living bone through a layer of apatite. It has
been shown that this apatite layer can be reproduced on their surfaces in an acellular and protein-free
simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma, and
that apatite thus formed is similar to the bone mineral in its composition and structure.
This evaluation of apatite-forming ability on implant material in SBF is useful for evaluating its in vivo
bone-bonding ability preliminary to animal experiments. When a bioactive material is implanted in a
living body, a thin layer rich in Ca and P forms on its surface. The material then connects to the living
tissue through this apatite layer without a distinct boundary. It has been shown that this apatite layer
can be reproduced on the surfaces of materials in SBF as well, and that apatite thus formed is similar to
bone mineral in its composition and structure. As bioactivity increases, apatite forms on the material
surface in a shorter time in proportion to this increase. The formation of apatite layers can be detected
by thin film X-ray diffraction spectrometry and/or scanning electron microscopy.
The apatite formed in the SBF is, however, similar to bone apatite in the following points.
— Ca-deficient type apatite.
— Lower Ca/P atomic ratio than stoichiometric apatite.
2+ + - -
— Containing some impurities such as Mg , Na , Cl , HCO .
— Low crystallinity.
NOTE 1 The material which forms apatite on its surface in vivo can bond to living bone, since this apatite is
biologically active. Their in vivo apatite deposition can be reproduced on their surfaces even in vitro in SBF. For
1) 2)
example, in vivo calcification on surfaces of Bioglass® , CaO-SiO glasses, Na O-CaO-SiO glasses, Cerabone®
2 2 2
3)
A-W, Ceravital® -type glass-ceramic, sintered hydroxyapatite and alkali-heat-treated titanium metal, are
correlated with in vitro calcification in SBF. However, this does not exclude the possibility that materials, which
do not form apatite on their surfaces in vivo, bond to living bone. For example, it is reported that such resorbable
materials as beta-tricalcium phosphate (Ca (PO ) ) and calcium carbonate bond to living bone without forming
3 4 2
an apatite layer on their surfaces.
NOTE 2 It has been reported that glasses with different compositions in the system Na O-CaO-SiO show
2 2
a correlation between bone-forming ability of materials implanted into a bone defect of a rabbit and apatite-
forming ability on its surface in SBF.
1) Trade names of products are 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) Trade names of products are 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.
3) Trade names of products are 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.
INTERNATIONAL STANDARD ISO 23317:2014(E)
Implants for surgery — In vitro evaluation for apatite-
forming ability of implant materials
1 Scope
This International Standard specifies a method for detecting apatite formed on a surface of a material in
simulated body fluid (SBF). It is applicable to implant surfaces intended to come into direct bone contact.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 14630, Non-active surgical implants — General requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14630 and the following apply.
3.1
apatite
group of calcium-phosphates including bone mineral and the main inorganic constituent of bones and
teeth similar to hydroxyapatite, which has the composition Ca (PO ) (OH)
10 4 6 2
2− − + 2+
Note 1 to entry: Bone mineral also contains ions such as C0 , F , Na and Mg .
3.2
apatite-forming ability
capability to develop apatite on the surface
3.3
bioactivity
property that elicits a specific biological response at the interface of the material, which results in the
formation of a bond between tissue and material
3.4
induction period
time to detect apatite formation on a surface of a specimen after soaking the specimen in simulated
body fluid
3.5
simulated body fluid
SBF
inorganic solution having a similar composition to human blood plasma without organic components
3.6
standard glass for evaluating apatite-forming ability
class of standard glasses with certain chemical compositions as shown in Annex B showing given apatite-
forming abilities in SBF and when implanted in an animal body
3.7
thin film X-ray diffraction spectrometry
TF-XRD
method for detecting minerals in a thin layer at the surface of a material from a diffraction pattern
obtained by X-ray with small glancing angle against the surface of the sample
4 Apparatus
4.1 Electric balance, capable of measuring a mass with an accuracy of ± 1 mg.
4.2 Water bath equipped with magnetic stirrer, to maintain temperature of the solution within the
range of (36,5 ± 2) °C and an accuracy of ± 0,2 °C.
4.3 pH meter, capable of measuring the pH of a solution with an accuracy of ± 0,01.
4.4 Thermometer, capable of measuring the temperature of a solution with an accuracy of ± 0,1°C.
4.5 Thin film X-ray diffraction spectrometer (TF-XRD), capable of detecting apatite formed in a thin
layer at the surface of a material.
4.6 Scanning electron microscope (SEM), capable of observing apatite grains and/or layers formed
on a plain surface of a material with a magnification up to × 10 000.
5 Test specimen
5.1 Specimen configuration and size
This International Standard allows specimens of any configuration and size derived from implant parts
and devices to be used. However, a disc or rectangular plate specimen is highly recommended, because
bioactivity of a material is evaluated by confirmation of apatite formed on the surface of the material
using TF-XRD and/or SEM. Recommended specimen dimensions are shown in Figure 1.
Dimensions in millimetres
a) Disc specimen b) Rectangular specimen
Figure 1 — Recommended specimen dimensions
5.2 Specimen preparation
5.2.1 General
This International Standard allows several options for specimen preparation. The specimens should be
machined, if necessary, to alter the configurations of original implants.
2 © ISO 2014 – All rights reserved

5.2.2 Basic machining procedure
In the case of a rectangular thin plate specimen as shown in Figure 1 b, the following procedure shall be
used. Specimens shall be ground us
...