ISO/TS 17576:2004

TECHNICAL ISO/TS
SPECIFICATION 17576
First edition
2004-01-15

Dentistry — Corrosion tests for amalgam
Art dentaire — Essais de corrosion des amalgames




Reference number
ISO/TS 17576:2004(E)
©
ISO 2004

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ISO/TS 17576:2004(E)
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ISO/TS 17576:2004(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
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The main task of technical committees is to prepare International Standards. Draft International Standards
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International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a
technical committee may decide to publish other types of normative document:
 an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
 an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee casting
a vote.
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further three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is
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International Standard or be withdrawn.
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.
ISO/TS 17576 was prepared by Technical Committee ISO/TC 106, Dentistry, Subcommittee SC 1, Filling and
restorative materials.
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ISO/TS 17576:2004(E)
Introduction
The development of this Technical Specification is the result of worldwide demand for test methods to
determine acceptability of dental amalgams for oral restorations in relation to corrosion and mercury vapour.
The test methods described in ISO 10271 are intended for dental metallic materials and are not suitable for
amalgams, due to the risk of formation of precipitates during the test. Furthermore, ISO 10271 does not cover
measurement of mercury vapour liberated during corrosion of amalgam.


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TECHNICAL SPECIFICATION ISO/TS 17576:2004(E)

Dentistry — Corrosion tests for amalgam
1 Scope
This Technical Specification provides two test methods and concomitant protocols to determine the corrosive
behaviour of dental amalgams and their tendency to release mercury vapour during corrosion. The methods
measure 1) the integrated current in a potentiostatic corrosion test and 2) the amount of released ions and
mercury vapour in a static immersion test.
This Technical Specification is not intended to set limits for the relevant parameters in the two tests described.
2 Normative references
The following referenced documents are indispensable for the application 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 1559:1995, Dental materials — Alloys for dental amalgam
ISO 3585:1998, Borosilicate glass 3.3 — Properties
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 10271:2001, Dental metallic materials — Corrosion test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
amalgam
alloy of mercury with one or more other metals
3.2
corrosion
deterioration of an amalgam by chemical or electrochemical reaction with its environment
NOTE This deterioration is manifest in the loss in mass of the amalgam, with a release of constituent elements or the
formation of an adherent film of reaction products.
3.3
electrolyte
liquid that contains ions whose combination allows the conduction of electricity
3.4
immersion test
test in which the sample is exposed to a corrosive solution without application of variable mechanical stresses
to the sample
3.5
potentiostatic test
test in which the electrode potential is kept constant
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ISO/TS 17576:2004(E)
4 Test methods
4.1 Potentiostatic corrosion test for dental amalgam
4.1.1 Specimen preparation
Prepare an amalgam specimen of the type for the measurement of compression strength, in accordance with
ISO 1559. Condition in air at (37 ± 2) °C for (7,0 ± 0,1) days.
Attach an insulated lead to the specimen for connection to the potentiostat.
Cover the connecting lead junction and all surfaces except one end of the specimen with an insulating
material, preferably by casting in epoxy resin. The temperature rise during setting of the resin shall not exceed
15 °C. This material shall not dissolve in or react with the electrolyte.
Wet-grind the exposed end of the specimen uniformly to ASTM 600 or FEPA 1200 using silicon carbide
surface abrasive paper. Wash with distilled water.
Eliminate the crevice between the amalgam and the embedding materials by casting or masking.
The testing laboratory may develop its own method of specimen preparation, provided the above procedures
are included and the conditions are met.
4.1.2 Reagents
4.1.2.1 Electrolyte, of volume W 300 ml.
Make up a fresh solution of NaCl [c(NaCl = 0,154 mol/l)] by adding (9,0 ± 0,1) g analytical grade NaCl to
600 ml water (ISO 3696, Grade 2), then make up this solution to (1000,0 ± 0,5) ml.
4.1.3 Apparatus
4.1.3.1 Corrosion cell.
Use a three-electrode corrosion cell holding the specimen (working electrode), a reference electrode probe,
and an inert counter-electrode (platinum or carbon is recommended).
4.1.3.2 Temperature control, consisting of a jacket and temperature control/circulator, or a temperature-
controlled bath, capable of maintaining (37,0 ± 0,5) °C in the cell.
4.1.3.3 Reference electrode and its control.
Use any standard reference electrode with a stable potential of known potential difference from a standard
hydrogen electrode (SHE). Control the potential at (0,000 ± 0,002) V vs. a saturated calomel electrode (SCE)
at 25 °C, equivalent to (0,2415 ± 0,002) V (SHE).
The reference potential values for some other common reference electrodes and corresponding values for the
control potential settings are shown in Table 1. Other electrodes can be used based on their known potential
difference from SHE.
4.1.3.4 Electronic potentiostat, capable of a current output W 100 mA, a voltage output W 10 V, and a
potential control accurate and stable to ± 1 mV.
The hardware/software used shall allow either recording the current for 24 h or integrating the current for 24 h.
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ISO/TS 17576:2004(E)
4.1.4 Test set-up
4.1.4.1 Temperature of the reference electrode
Measure the temperature of the reference electrode (4.1.3.3). If necessary, adjust the temperature to
(25 ± 1) °C by the control potential using the temperature coefficient for the given electrode type.
Temperature coefficients and examples of potential correction are shown in Table 1.
Table 1 — Potential settings for different reference electrodes and temperatures
of the reference electrodes
Reference potential Control potential setting
Temperature /V (SHE) /V
Reference Reference
[1]
coefficient
when the temperature of the when the temperature of
electrode type electrolyte
V/K
reference electrode is the reference electrode is
18 °C 25 °C 37 °C 18 °C 25 °C 37 °C
Saturated calomel
−4
Saturated KCl 0,2468 0,2415 0,2325 −0,005 0,000 0,009
−7,50 × 10
(SCE)
−4
1,0 M calomel 1 mol/l KCl 0,2817 0,2800 0,2771 −0,040 −0,039 −0,036
−2,40 × 10
−5
0,1 calomel 0,1 mol/l KCl 0,3342 0,3337 0,3329 −0,093 −0,092 −0,091
−7,00 × 10
−4
0,1 silver chloride 0,1 mol/l KCl 0.2927 0,2881 0,2803 −0,051 −0,047 −0,039
−6,50 × 10

4.1.4.2 Positioning of the reference electrode
During the polarization part of the procedure, place the reference electrode probe close to the working
electrode (amalgam) surface without touching the surface or shielding substantially the specimen surface.
Also, the electrolyte of the reference electrode shall not contaminate the electrolyte in the vicinity of the
amalgam. This is commonly achieved by placing the reference electrode in a separate compartment and
using a “salt-bridge” between the reference electrode compartment and the main cell. The salt-bridge is a tube
filled with the electrolyte and ending in a capillary (“Luggin capillary”), the end of which is placed close to the
tested surface. The tip of the capillary should be at a distance from the amalgam surface equal to about two
outer diameters of the tip.
4.1.5 Test procedure
Fill the corrosion cell (4.1.3.1) with electrolyte (4.1.2.1). Leave the cell open to the atmosphere. However, the
cell should be covered with a lid to prevent excessive evaporation of the electrolyte.
Using the temperature control (4.1.3.2), heat the cell and maintain at a temperature of (37,0 ± 0,5) °C.
Insert the specimen, connect the specimen and electrodes to the potentiostat (4.1.3.4) (no potential control)
and wait (10,0 ± 0,1) min. During this potential stabilization it is advisable to stir the solution, e.g. using a
magnetic stirrer and a stirring bar in the cell.
Record the potential at the end of the (10,0 ± 0,1) min exposure period. Stirring also may be used during this
open-circuit potential measurement.
Set the potentiostat to the appropriate control potential (see Table 1) and time (24 h). Apply the potential and
record or integrate current for (24,0 ± 0,2) h. During this polarization part of the test, the solution should
remain stagnant (no stirring).
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ISO/TS 17576:2004(E)
4.1.6 Data acquisition and processing
a) Coulometer method
A convenient method of data acquisition is to use an electronic current integrator (coulometer) in the
circuit between the potentiostat and the cell. The reading of the coulometer after 24 h of polarization is the
anodic charge.
b) Computer-controlled potentiostat method
An equally convenient procedure is to use a computer-controlled potentiostat with a program for
potentiostatic control and software which allows post-test integration of the recorded current as displayed
1)
on the screen .
c) Data-logging and integration method
If neither a) nor b) is available, record the polarization current using any available data acquisition system.
The integration then can be performed by averaging all the current data and multiplying the average
current, in amperes, by the total exposure time, in seconds (assuming that the time between current
...