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IS0
TECHNICAL
TR 10271
REPORT
First edition
1993-06-01
d
Dentistry - Determination of tarnish and
corrosion of metals and alloys
Art dentaire - Détermination du ternissement et de la corrosion des
métaux et alliages
c
Library / Bibliothbque
DO not mmwe I Ne pas enlever
Reference number
ISO/TR 10271 :I 993(E)
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ISO/TR 10271 :1993(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide
federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
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. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
The main task of technical committees is to prepare International Stan-
dards, but in exceptional circumstances a technical committee may pro-
pose the publication of a Technical Report of one of the following types:
- type 1, when the required support cannot be obtained for the publi-
cation of an International Standard, despite repeated efforts;
- type 2, when the subject is still under technical development or where
for any other reason there is the future but not immediate possibility
of an agreement on an International Standard;
- type 3, when a technical committee has collected data of a different
kind from that which is
("state of the art", for
Technical Repo
of publication,
national Standa
be reviewed until the data they provide are considered to be no longer
valid or useful.
ISO/TR 10271, which is a Technical Report of type 2, was prepared by
Technical Committee ISOflC 106, Dentistry, Sub-committee SC 2,
Pros thodon tic materials.
Annex A of this Technical Report is for information only.
8 IS0 1993
,
All rights reserved. No part of this publication may be reproduced or utilized in any form or
by any means, electronic or mechanical, including photocopying and microfilm, without per-
I
mission in writing from the publisher.
l
International Organization for Standardization
1
Case Postale 56 CH-1 21 1 Genève 20 Switzerland
I
in Switzerland 1
Printed
ii
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ISO/TR 1027 1 :I 993(E)
TECHNICAL REPORT
Dentistry - Determination of tarnish and corrosion of
metals a-nd alloys
3.1 corrosion: Physico-chemical interaction be-
1 Scope
tween a metal or an alloy and its environment result-
ing in a partial or total destruction of the metal or in
This Technical Report indicates currently available test
a change of its properties.
'methods for the tarnish and corrosion behaviour of
metals and alloys used in dentistry. It applies to all
3.2 tarnish: Type of corrosion as (surface change)
metals and alloys introduced to the oral cavity such
characterized by surface discoloration.
as:
3.3 loss of substance: Reduction of mass of the
- direct filling metals and alloys;
specimen by corrosion.
- cast metals and alloys (including implants);
3.4 pitting corrosion: Corrosion resulting in pits; i.e.
- wrought metals and alloys (including implants);
cavities extending from the surface into the metal.
- solderlbraze filler metals and alloys;
3.5 crevice corrosion: Corrosion associated with,
a narrow
and taking place in, or immediately around,
- deposited metals and alloys;
aperture or clearance.
- combinations of the above.
3.6 corrosion product: Substance formed as a re-
sult of corrosion.
2 Normative references
3.7 accelerated test: Corrosion test carried out un-
der more severe conditions to yield results in a
orhe following standards contain provisions which,
shorter time than in service.
through reference in this text, constitute provisions
of this Technical Report. At the time of publication,
3.8 in vitro test: Test which predicts service or
the editions indicated were valid. All standards are
clinical performance using physical, chemical and/or
subject to revision, and parties to agreements based
electrical systems in the test laboratory.
on this Technical Report are encouraged to investi-
gate the possibility of applying the most recent edi-
3.9 extraction product: Product soluble in an ex-
tions of the standards indicated below. Members of
traction vehicle, obtained from a material.
IEC and IS0 maintain registers of currently valid In-
ternational Standards.
3.10 extraction vehicle: Liquid selected specifically
to obtain extraction products from a material, and
IS0 1559:1986, Dentistry - Alloys for dental
simulating human body fluids.
amalgam.
3.11 animal test: Test which relates to clinical per-
ISO/TR 7405: 1 984, Biological evaluation of dental
formance preliminary to use in humans,
materials.
3.12 clinical trial: Test designed for and used in the
human oral cavity.
3 Definitions
For the purposes of this Technical Report, the follow- 3.13 artificial saliva: Test medium which simulates
ing definitions apply. natural saliva for the performance of a specific test.
1
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ISO/TR 10271 : 1993(E)
4.2.7 Crevice corrosion test
4 Requirements for tests
See table 1.
4.1 Test specimens
4.2.8 Corrosion cracking test
The materials shall be processed according to the
manufacturer's instructions.
See table 1.
4.1.1 General test specimens
4.2.9 Tarnish test
Test specimens applicable to the tarnish test, loss of
See table I.
substance, pitting corrosion and crevice corrosion are
described in the relevant tests. See table 1.
5 Deleterious effects
4.1.2 Test specimens for filling material
The deleterious effects of tarnish and corrosion may
The test specimens for filling materials shall be pre-
be defined in three areas.
pared in accordance with IS0 1559, table 1 or appli-
cable national standards.
5.1 Safety: generation of harmful corrosion 0
4.1.3 Specimens for tensile testing
products
Tensile specimens shall be prepared as shown in the
Corrosion and tarnish denote the formation of metal
applicable standard with reference to the test method.
compounds, whether formed by simple oxidation-type
reactions or by the release of metal or metal ions. The
harmful effects of these metals or metal compounds,
4.2 Tests
such as oxides, sulfides, chlorides, metal organics or
other species need evaluation for their effect on the
4.2.1 Static immersion test
soft and hard tissues and other parts of the body, in
accordance with ISO/TR 7405.
This test requires placement in a test solution for a
specified period of time.
Harmful effects may include, for instance, inflamma-
tory, allergenic, cariogenic, mutagenic, carcinogenic,
toxic, cytotoxic, teratogenic, or distasteful effects.
4.2.2 Rotating immersion test
Electrical currents and pain can occur due to the use
The apparatus usually consists of a vertical wheel,
of dissimilar metals and alloys, and galvanic action.
driven by an electric motor at a specified speed. The
wheel consists of a material that neither is attacked
by the test solution nor can interfere with the test
5.2 Efficacy
result in any other way. The wheel shall be provided
0
with fittings so that the specimens can be attached
5.2.1 Loss of substance
to it. The test solution is placed in such a manner that
the specimens are immersed in the solution for each
If the loss is sufficient to reduce section thickness
revolution of the wheel.
significantly, it is conceivable that enough mechanical
strength will be lost that failure will occur by bending
4.2.3 Loss of substance test
or fracture. Where the loss of material occurs by
pitting or roughening, sites can be formed for plaque
Immersion, electrochemical, nuclear and photometric
deposition and growth. Pitting may initiate fatigue
tests are described in table 1.
fracture.
4.2.4 Potentiodynamic polarization test
5.2.2 Metal/non-metal interface
See table 1.
Where corrosion occurs at the interface of metal with
ceramic, plastic, cement, etc., the bond or adhesion
4.2.5 Potentiostatic polarization
between the two materials may be weakened or de-
stroyed, or a crevice can be created or enlarged. The
See table 1.
result may be loss of the non-metal, discoloration of
the non-metal or increased corrosion within the
4.2.6 Pitting corrosion test crevice. At the interface between metal and hard or
soft tissue, corrosion is more likely because of oxygen
See table 1. depletion.
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ISO/TR 1027 1 :I 993(E)
5.2.3 Stress corrosion cracking 6.2 Testing regarding efficacy
Failure may occur with the combined action of cor-
rosion and stress.
6.2.1 From 6.1 a) to cl, determine rate of loss of
substance in vitro.
5.2.4 Corrosion fatigue
Test for loss of substance in vivo (providing that re-
Service life may be reduced from repeated or fluctu- action products are not found harmful).
ating load when occurring in a corrosive environment.
Translate this loss of thickness to millimetres per
year. Compare with average lifespan of restoration
5.3 Aesthetics
and with normal thicknesses found in restorations of
the type for which the metal or alloy would be used.
Corrosion may result in loss of lustre since reflected
light is diffused, giving the appearance of a discolor-
ation. Actual discoloration results from coloured re-
6.2.2 Pitting corrosion is tested as follows.
action products which are tenacious enough to remain
on the surface. Such coloured or uncoloured reaction
Determine density and dimension of pits on samples
products might even protect against further reaction.
tested in 6.1 a) to cl.
Well known coloured reaction products are silver and
copper sulfides. With many other elements being
Check in vivo results on samples from 6.2.1.
tested for use in dental alloys, other coloured com-
e
pounds are possibilities in future alloys. Discoloration
in itself, where the coloured film is not a part of an-
6.2.3 Interface corrosion (including crevice and re-
other corrosion reaction, does not affect safety or ef-
duced oxygen corrosion) is tested on specially de-
ficacy. Therefore this aspect can be ignored in this
signed specimens in vitro for corrosion in an
context and the market will be the determining factor
experimental crevice.
as to whether a discolouring metal is acceptable.
Repeat in vivo tests and correlate between in vitro
and in vivo values. Relate the rate of penetration to
6 Proposal for future testing
normal restorations and estimate lifespan.
It is well established that no single test can give a
complete indication of the reaction between metal or
6.2.4 Stress corrosion cracking is assessed by for-
alloy, and the oral environment. This Report therefore,
mation and propagation of cracks when subject to a
suggests only types of tests and the type of infor-
corrosive environment under stress and dynamic load.
mation to be gathered which will lead to an Inter-
national Standard.
6.2.5 Alloy combinations are assessed by similar
6.1 Testing regarding safety
tests to 6.2.1, 6.2.2 and 6.2.3, run on soldered sam-
ples where a solder is recommended for a particular
a) immersion tests (including depleted oxygen tests);
alloy.
0
b) electrochemical tests (including galvanic coupling);
c) identify and quantify corrosion products:
6.3 Testing regarding aesthetics
- identify harmful corrosion products and rate of
release,
6.3.1 Test by the methods of 6.1 a) and b)
- establish acceptable limits of concentration of The acceptance of discoloration may vary consider-
ably depending on the standards required by peoples
harmful products based on release ratio in the
of differing social origin. The specification shall be set
oral cavity.
in such a manner that it can be varied according to
local circumstances and in a voluntary form so ac-
d) correlate in vitro with in vivo. From identification
of corrosion products, it may be inferred that such ceptable alloys will not be ruled out.
products will be produced in vivo. Such products
should be evaluated for biocompatibility. The sim-
ple conclusion that harmful species can be formed 6.3.2 Tenacity of film is assessed by a toothbrush
and that injury to the patient can be expected may test as prepared by several researchers (see
be the basis for rejection of a metal or alloy. annex A).
3
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ISO/TR 1027 1 :1993(E)
Table 1 - Available corrosion tests for dental materials -
malaam allovs
~-
Specimen
Test typelsource Test apparatus Test medium Test conditions I Specimen
Test requirement
design preparation
Immersion Vessel with 50 g Na,S, 6 specimens
Immersion Embedded polish,
Specimens shall
15 ml solution for 1 O00 ml distilled
3 months specimens 1 pn diamond
exhibit 95 %
each specimen
H,O changed IS0 1559 paste
compressive
each week
strength of non-
corroded specimen
Potentio-dynamic Electrochemical Artificial saliva:
Immersion Embedded polish,
7 day specimens
polarization closed, stirred
0,4 NaCI, specimens
1 hrn diamond rupture potential
system
0,4 KCI, O, depleted IS0 1559
Daste not less than E Cori
NlOM
0,795 g of
by Nz + 250 mV. 1)
CaC1.2H2O. bubbling 7 days
No crevice or
0.78 Ci Of
stress corrosion
NaH,P0,2H,O.
0,005 g of
Na,S.2H2O,
1 g urea,
1 O00 ml distilled
H2O
Extraction Autoclave oven, Artificial saliva Incubation at
12 x 3 mm disc 600 lo 1 200 Quantitative analy-
teflon-lined NF 30-S91 37 oc
emery paper sis of extract
AFNOR borosilicate glass for 120 h
Microphotometric Vessel containing
Artificial saliva 4 samples em-
Pellets embeddei Amalgam Reproducible
artificial saliva 3 stock solution bedded in each
in polyester, thici triturated in vacuo screening test us-
Hong Kong Microscope with :lo0 ml) specimen
to IO-' torr, ing discoloration
photometer NaH,PO, 56 37 oc
VaCl 150 22 oc
VH,CI 22 50 "C
:itrate.PH, 2.2
-attic acid 7.0
t dist H,O to
1 000ml
Jrea 20
Jric acid 1.5
VaOH 0,4
t dist H,O to
? O00 ml
VaHCO, 60
VaSCN 20
t dist H,O to
O00 ml
I
tlectrochemical Neutron Irtificial saliva
ïhermal neutron 5 x 10 x 0,3 mm 1 O00 grit Release of Cu. Hg,
ifter immersion irradiation gamma iee 2 above 'lux for 1 h
paper grind
Zn
ray spectropho- 30 "C to 100 oc
ùlOM tometry mmersion 2 h to
SEM X-ray dif- 30 days
fraction
Iectrochemical Epoxy resin cylin-
Mificial saliva 1 mm hemi-
Polished with dia- Comparison of in
iolarization curves der three elec- n vivo
spherical buttons mond paste vitro and in vivo re-
nd in vivo trode system,
3UltS
button in denture
rustralia
inear polarization Linear polarization irtificial saliva
$7 OC 45 days, 1 mm2 to 14 mmi
'olished with fine 4nodic and
nd in vivo
)aboon teeth ;amples
mery discs :athodic tafel
Primates
O80 h I
jloDeS
I SA
) Start at E corr, make an anodic sweep to + 2 mV, reverse direction to E corr - 1 mV/s. Express in bA/cmz
4
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ISO/TR 1027 1 :1993( E)
Table 2 - Available corrosion tests for dental materials - Cast metals and alloys
Specimen
Specimen
Test type/rource Test apparatus Test medium Test conditions Test requirements
design preparation
Polish with 1 pm loss of
Immersion Vertical wheel at Na,S 0,l moll1 Specimens im- Embedded speci- Darkening,
diamond oaste
a speed of Na$ 7.8 gli mersed mens lustre compared to
DIN 1 r/min Na$ 22,2 g/i 10 s to 15 s per untreated speci-
Na$ 7 to 9 H,O revolution for men
distilled H,O 72 h
2 specimens Polish with 1 pm Visual inspection
Loss of substance, Vessel with test Lactic acid 37 oc
diamond paste
pitting corrosion medium 0.1 moll1 weigh specimens
NaCl 0,l moll1 to I 0,l mg
DIN PH 2 hang vertical in
distilled H,O aerated
I
solution 7 days
Lactic acid 37 "C 2 specimens Polish with 1 pm Average decrease
Crevice corrosion Vessel with test
I medium 0.1 moll1 weigh specimens diamond paste in mass mg/cm'
Naci 0.1 moi/i to f 0,l mg on compared with
DIN
plate glass and above test
PH 2
distilled H,O solution,
aerated 7 days
I
Stress corrosion Vessel with test Lactic acid 37 OC 2 rolled sheets Rolled around cyl- Visual inspection
0,l moll1 specimens stored 70 x 8 x 0,5 mm inder for cracks
I medium
NaCl 0,l moi/l in aerated as needed, and
DIN
PH 2 solution 7 days bent around a
H20 1 O mm diameter
distilled
cylinder
% Na$ 1 rlmin rotation; 2 x 1/4 x 4 in Mounted in acrylic Microscopic in-
Tarnish Vertically rotating 0,5
wheel with eight 15 s immerse grind spection
1,5 g PCS
USA lin holes for mould; 0,02 in 600 grit polished
sDecimens 45 s withdraw; 0,3 pm AI,O,
mech. wiped
Linear polarization Linear polarization Artificial saliva 37 "C 45 days 4 mm' to 14 mm' Polished with fine Anodic and
baboon teeth samples emery discs cathodic tafel
and in vivo
Primates 1 080 h slopes
USA
Static Vessel with test Lactic acid 1 ;,"y immersion 6 specimens Pickling, blasting, Analytical determi-
immersion medium 0.1 moll1 32 x 10 x 1,5 mm grinding to nation of metal ions
Maci O,I moi/i ASTM 600 grit e.g. AAS or ICP
= FEPA 1 200
DIN 13906-2
pH 2.3
Sic paper
I
Naked eye or
Tarnish Vertically rotating 0,l mol % Na,S 10xlOxlmm Pickling, blasting,
microscope do not
wheel with eight 10 s to 15 s castings grinding, polishing,
1 pm diamond reveal darkening or
Germany 1-in holes for per min,
specimens 4 320 dippings paste loss of lustre
Glass filter 100 ml modified 15 h to Rectangular foils Ground Not available
Nuclear
tracer frits, Fusayama sol- 1 week 1 cm' of Au alloy 1 O00 grit paper
neutron flutes ution gamma ray spec- cylindrical discs
NlOM trometry 5x2mm
titanium
I
Immersion Vessel with test 15x20~1 mm Ground to Discoloration limit
medium Au 58 I 800 grit to 7.5 year
Japan Au Pd Ag 8+/C6-
Ag Pd to 10 year
7+/C6-
12 x 3 mm disc Poishing 1 pm Polarization poten-
polarization closed system dipping contact diamond paste tial
E coir + 100 mV
AFNOR E coir + 200 mV
37 "C Section Sic 1 200
Potentiostatic Electrochemical Isotonic solution Measure
closed system, Artificial plasma Air or argon 0.2 cm' 1 pm diamond
intensity pA
9g O mV/s.
France magnetic NaCl 1 paste potential mV/s
agitator PH 7,4 argon bubbling rest potential
deionized water
Pt counter after 15 min and
NF 97141
electrode 24 h
1) Time and polarization potential depend on concentration of extracted products.
5
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ISO/TR 1027 1 :1993(E)
Specimen
No.
Test typelsource Test apparatus Test medium Test conditions I Specimen I preparation Test requirements
design
18
Immersion Vessel with test 0,l % Na,S 37 OC f 2 OC Various Not available Discoloration
solution 50 rnl 3 days 10 year 7 + /6 -
Japan
~
Specimen
- I
14 1 Static
Vessel with test Lactic acid 7 days immersion 6 specimens Pickling, blasting, Analytical determi-
1 immersion medium 1 0,1 moil1
37 OC 32 x 10 x 1,5 mm grinding to nation of metal ions
NaCl 0,l molli
ASTM 600 grit e g AAS or ICP
I DIN 13906-2
PH 2.3 = FEPA I 200
SIC paper
-
15 Tarnish Vertically rotating % Na,S
0,l mol Immersed 10 x 10 x 1 mm Pickling, blasting, Naked eye or
wheel with eight
10s to 15s castings grinding, polishing, microscope do not
Germany 1-in holes for
per min, 1 lm diamond reveal darkening or
specimens
4 320 dippings paste loss of lustre
over 3 days
-
19 Immersion Vessel with 0,l % Na,S
37 OC f 2 "C Au Pd Ag Not available Discoloration
test solution 50 ml 3 days Au 15 10 year 7+/6-
Japan
Au Ag 30+
20 OC -three 6 tensile Specimens having Treated and un-
Electrochemical Electronics with Artificial saliva 37
reference elec- (see 2) specimens shall specimens a solder joint, treated specimens
NlOM trode and Pt be subjected to 3 specimens un- subjected to tensile
counter electrode potential of treated test with cross
E corr + 300 mV
head speed of
0,5 mmlmin
No.
Test type/source Test apparatus Test medium Test condRions Specimen preparation Specimen Test requirements
design
21 Immersion Vessel with 50 g Na,S 6 specimens Immersion Embedded polish, Specimens shall
15 ml solution for 1 O00 rnl distilled 3 months specimens 1 Nm diamond exhibit 95 %
NlOM each specimen H,O, changed IS0 1559 paste compressive
each week strength of non-
corroded specimen
-
No. Test typelsource Test apparatus Test medium Test conditions specimen preparation Specimen Test requirements
design
22 Not available
No. Test typelsource Test apparatus Test medium Test conditions Specimen
Specimen Test requirements
design preparation
23 Not available
6
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ISO/TR 1027 1 :1993(E)
Table 8 - Available corrosion tests for dental materials - Combinations
-
Specimen
Specimen Test requirements
Test typÿsource Test apparatus Test medium Test conditions design preparation
10.
-
Pickling, blasting, Analytical determi-
6 specimens
7 days immersion
Vessel with test Lactic acid
14 Static
grinding to nation of metal ions
32 x 1 O x 13 mm
37 oc
immersion medium 0,l moll1
e g AAS or Icp
ASTM 600 grit
NaCl 0.1 mol/l
= FEPA 1 200
PH 2,3
DIN 13906-2
Sic pap
...
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