ANALYSES of ALTERNATIVES
non-confidental report
Chromium trioxide - Functional chrome plating with decorative character for dental and
surgical instruments (issue date 2015-09-18).
Legal name of applicant(s):
W&H Dentalwerk Bürmoos GmbH
Bien Air Dental S.A.
Sirona Dental GmbH
SycoTec GmbH & Co. KG
Submitted by:
W&H Dentalwerk Bürmoos GmbH
Substance:
Chromium trioxide EC No: 215-607-8, CAS No: 1333-82-0
Use Title:
Functional chrome plating with decorative character
Use Number:
3
The intent of this evaluation of analysis of alternatives of metallic coatings from chromium
trioxide is to point out the differentiation of requirements on key functionality and technical
feasibility related to devices or hand-pieces of dental practices, dental hospitals, dental
laboratories and microsurgery. Therefore this document contains additional statements
respectively supplements to the considered “List of plating alternatives categorized” (in Table
5) referring to the existing (non-confidential) report of “Analysis of Alternatives” released on
12.08.2015
via
http://echa.europa.eu/addressing-chemicals-of-concern/authorisation/applications-forauthorisation/-/substance-rev/10111/term which is mainly considered and issued by sanitary and
automotive sector.
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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Supplement to
3.3.2. Key functionalities of chromium trioxide based electroplating according to
dental and surgical devices:
Tab. 1. Sector Specific key functionalities of chromium trioxide based electroplating
Key Functionality
Chemical resistance
/Corrosion protection of
substrate
dental (surgical) device surfaces
Up to 336 h EN ISO 21530
disinfectants and cleaning agents, continuous immersion tests
No visual degradation of the coating or corrosion of the substrate
material after testing with different chemicals.
Thermal disinfection ISO EN 15883-3
Chemical + Temperature
change/heat- resistance
Wear/abrasion resistance
Aesthetics
Hot steam sterilisation 135°C (ISO 17664)
Haptic, non-slip grip
Adhesion
Biocompatibility
Ni-leaching
Hygienic aspects
OEM Specification
Surface has to be free of any kind of defects as pores, cracks, and
blistering. Bright homogenous finish quality. Colour testing to EN
ISO 11664.
No or only little smoothening or planing of sand blasted pre-treated
surfaces depending on coating thickness and surface energy.
Evaluation per IEC 62366
Cross cut test EN ISO 2409 (GT0 to GT1) after hot stem
sterilisation cycling tests on Brass substrates
ISO EN 10993-1 (no cytotoxic, irritating and/or sensitisation
effects)
ISO EN 10993-12 (limitation for leachable substances)
< 0,5µg/cm2 per week
Surface has to be free of any kind of defects as cracks, blistering
and pores as growth sites for microbes or diminished cleanability .
Supplement to
3.3.2.1 Chemical resistance/ Corrosion protection of substrate:
The coating has to be adequately (corrosion-) resistant against common cleaning and
disinfectant solutions and thermal disinfection which are used for reprocessing treatment of
dental/surgical devices.
Moreover the coatings have to build a dense barrier to prevent chemical agents to penetrate
and attack the substrate material and protect this from corroding.
For evaluation immerging test as per EN ISO 21530 and high cycle thermal disinfection
treatments are performed.
Supplement to
3.3.2.4. Nickel leaching and biocompatibility
The surfaces of product parts which come in contact with patients must not cause any toxic,
irritating and/or sensitisation effects to human skin or body according to standard 10993-1
(Biological evaluation of medical devices).
Supplement to
3.3.2.5. Adhesion
The adhesion of the coatings must not degrade after several disinfection, thermal disinfection
and sterilization treatments/cycles.
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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Supplement to
3.3.2.7. (Chemical-) and Temperature change/heat resistance
Hot steam sterilisation is a combination of chemical and temperature changing exposure. The
coating has to fulfill requirements on durable adhesion to substrate, corrosion resistance and
sealing performance for a high number of sterilization cycles up to 2000 sterilisation cycles
Manufactures have to provide information for the processing of re-sterilisable medical devices
per ISO 17664.
Supplement to
3.3.2.10. Aesthetics:
Surface has to be free of any kind of visible defects as pores, cracks, and blistering. Bright
silvery colours with homogenous finish quality are required for clean and hygienic
characteristic. Evaluation is performed by visual inspection using specific internal reference
samples.
Haptic, non-slip grip
Safe handling of devices must be ensured during treatment (ISO 14457). Good grip is mostly
achieved by roughened handle surfaces.
Evaluation according to IEC 62366 (Application of usability engineering to medical devices)
Supplement to
5. General Overview on sector specific approval processes for
5.x Dental / Surgical Sector :
Dental and surgical precision devices are used for the preparation and processing of human
dental and bone tissue. These products are subjected to the directive 93/42/EWG – Medical
devices and thus have to fulfill specific requirements on reprocessing in terms of cleaning,
disinfection, thermal disinfection and sterilization.
For premium-quality products with high global export rate also design and aesthetics as well as
the product lifetime (life time warranty) is an important basic requirement, which is currently
provided through the use of metallic coatings from chromium trioxide.
The fabrication of dental precision devices and instruments requires a great manufacturing
expertise. The production of several high-precision small parts with closest tolerances (in the
range of microns) is only (economically) feasible by the use of brass alloys because of their
good machinability and dimensional stability.
Brass as basic material on the other side only offers a restricted chemical resistance, so it has
to be protected against aggressive cleaning and disinfectant solutions and sterilization
procedures by coating.
Up to now there is no economically and technically feasible alternative to the metallic coatings
from chromium trioxide which is confirmed by several experiments on various new coating
systems including PVD, CVD, some lacquer Technologies, Ni-Co platings and anodized
aluminum surfaces.
An increase of manufacturing costs and / or loss of product quality would lead to an
aggravation of the already tight competitive situation especially with Asian or non-EU
manufacturers so that production location in Europe would become even less attractive for
necessity of profit-oriented companies.
Any new and following potential alternatives for chromium trioxide for use in dental sector
must be in compliance with the high demands and requirements regarding their critical
performance properties (Tab.1.) within manufacturing processes and their final use.
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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Supplement to:
7. Suitability and availability of possible alternatives
assessment: dental / surgical devices.
for sector specific
7.1.1. Alternative 1: trivalent chromium plating:
Conclusion of Technical feasibility: Not an alternative to coatings from chromium trioxide
because:




Intricate control of electrolyte baths as result of extreme sensitivity to bath impurities
Deviation of silvery-bluish color to yellowish brownish color does not fulfill the aesthetic
requirements
Too little process stability for assuring homogenous constant color shade.
Insufficient corrosion and wear resistance deduced from automotive and sanitary
requirements and assessments
chemical resistance /corrosion
protection
Cleaning and
Substrate
disinfectant
compatibility to solutions and
brass alloys
thermal
disinfection
Hot steam
sterilisation
(change/heatresistance)
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
Biocompatibility &
Nickel Leaching
(no toxicity)
yellowish
brownish color
7.1.2. Alternative 2: PVD based processes – lacquer + PVD + lacquer and PVD metal
Conclusion of Technical feasibility: Not an alternative to coatings from chromium trioxide
because:
PVD Metal
 PVD Metal: microporous morphology of coatings results in insufficient sealing and
corrosion protection of the substrate against hot water steam and cleaning/disinfectants
chemicals
 Lower Adhesion strength for coating thickness higher than 2-5 µm.
Lacquer + PVD-Systems
 Poor temperature change/heat- resistance because of different thermal expansion
behavior between substrate, lacquer- and PVD-layer results in delamination and
infiltration of lacquer coating during hot steam sterilization.
chemical resistance /corrosion
protection
Cleaning and
Hot steam
Substrate
disinfectant
sterilisation
compatibility solutions/
(change/heatto brass alloys thermal
resistance)
disinfection
not directly on
brass / precoating
Wear/abrasion Adhesion to
substrate
resistance
poor after
sterilisation of
lacqer
containing
systems
Aesthetics/
Decorative
Biocompatibility
& Nickel
Leaching (no
toxicity)
depending
on deposed
metal
depending on
deposed metal
and lacquer
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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7.1.3. Alternative 3 : Satin & black anodized Aluminum:
Conclusion of Technical feasibility: Not an alternative to coatings from chromium trioxide
because:



black, gray, dark colors do not fulfill the requirements to bright shiny surface
restricted to Aluminum substrate only. Low strength of Aluminum substrates
Insufficient chemical resistance of anodized aluminum according alkaline containing
cleaning/disinfectant agents.
chemical resistance /corrosion
protection
Substrate
compatibility to
brass alloys
Cleaning and
disinfectant
solutions/
thermal
disinfection
only for Al
substartes
poor resistance
aganst thermal
desinfection
Hot steam
sterilisation
(change/heatresistance)
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
Biocompatibility
& Nickel Leaching
(no toxicity)
only for Al
Substartes
7.1.4. Alternative 4: Chromium free electroplating: multi-component coatings
systems (Cu,Ni,Zn,Ni,Co) gold and platinum electroplating, zinc electroplating:
Conclusion of technical feasibility: Not an alternative to coatings from chromium trioxide
because:



Coatings do not fulfill the aesthetic requirements if golden or grey
Cu, Zn based coatings are not usable for sterilization and thermal disinfection
As Ni-Co Multilayer: coating thickness very high and poor resistance against frequent
sterilization
chemical resistance /corrosion
protection
Substrate
compatibility to
brass alloys
Cleaning and
disinfectant
solutions/
thermal
disinfection
Hot steam
sterilisation
(change/heatresistance)
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
Biokompatibility
& Nickel Leaching
(no toxicity)
depending on
metal
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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7.1.5./9. Alternative 5 Wet lacquering and Alternative 9: Powder Coating:
Conclusion of technical feasibility: Not an alternative to coatings from chromium trioxide
because:
 Insufficient sterilization/thermal-heat resistance
 Poor wear resistance because of low hardness of lacquers compared with metal surfaces
 Larger coating thickness (> 80 µm) leads to smoothening of pre- roughened surface
and a loss of slip resistance
 Minor value and aesthetic impression of lacquered surfaces compared with metal
surfaces
chemical resistance
/corrosion protection
Substrate
compatibility
to brass
alloys
Cleaning and
disinfectant
solutions/
thermal
disinfection
Hot steam
Adhesion to
sterilisation
Wear/abrasion
substrate
(change/heat- resistance
resistance)
Aesthetics/
Decorative
coating
thickness
ideally < 50
µm
low hardness
of lacquer
Biocompatibility
& Nickel
Leaching (no
toxicity)
depending on
lacquer
7.1.6 Alternative 6: CVD - Chemical Vapor Deposition:
Conclusion of technical feasibility: Not an alternative to coatings from chromium trioxide
because:
 High process Temperatures > 800°C not applicable for temperature sensitive substrates
as brass
 Do not fulfill the aesthetic requirements if golden, grey or black
 CVD coatings do not provide sufficient sealing and corrosion protection of the substrate
against hot water steam and cleaning/disinfectants chemicals
chemical resistance /corrosion
protection
Cleaning and
Substrate
disinfectant
compatibility to solutions/
brass alloys
thermal
disinfection
Hot steam
sterilisation
(change/heatresistance)
not directly on
brass / precoating
depending on
substarte
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
depending on
substrate and
pre-coatings
black/dark
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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Biocompatibility
& Nickel Leaching
(no toxicity)
7.1.7. Alternative 7: DLC - Diamond Like Carbon:
Conclusion of technical feasibility: Not an alternative to coatings from chromium trioxide
because:




Not directly applicable on brass substrates, pre-coating is required
Poor adhesion performance on soft substrate materials like brass
Black color does not fulfill the aesthetic requirements on bright shiny surfaces
Limited sterilization cycles on pre nickel-coated substrates
chemical resistance /corrosion
protection
Cleaning and
Substrate
disinfectant
compatibility to solutions/
brass alloys
thermal
disinfection
Hot steam
sterilisation
(change/heatresistance)
not directly on
brass / precoating
depending on
subtarte
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
depending on
substrate and
pre-coatings
black/dark
Biocompatibility
& Nickel Leaching
(no toxicity)
7.1.8. Alternative 8: Electroless Nickelplating:
Conclusion of technical feasibility: Not an alternative to coatings from chromium trioxide
because:


Biocompatibility according sensitization effects of human skin cannot be guaranteed,
nickel leaching
Minor aesthetic of finish quality due brightness and brilliance of color
chemical resistance /corrosion
protection
Substrate
compatibility to
brass alloys
Cleaning and
disinfectant
solutions/
thermal
disinfection
Hot steam
sterilisation
(change/heatresistance)
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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Biocompatibility &
Nickel Leaching (no
toxicity)
7.1.10. Alternative 10: Stainless steel (alternative substrate)
Conclusion of technical economical economic feasibility: Not an alternative to coatings from
chromium trioxide because:


chemical resistance is depending on steel grade. Stainless steel grades with good
machinability have only limited corrosion resistance due to high cycle reprocessing.
Steel grades with excellent corrosion resistance are problematic in machining and
processing small precision parts with complex machining geometry and result in much
higher production costs and lower processing quality (increasing defectives and major
increase of machining costs)
chemical resistance /corrosion
protection
Substrate
compatibility to
brass alloys
Hot steam
Cleaning and
sterilisation
disinfectant
(temperature
solutions/ thermal
change/heatdisinfection
resistance)
Wear/abrasion
resistance
Adhesion to
substrate
Aesthetics/
Decorative
depending on
steel grade
Biocompatibility
& Nickel Leaching
(no toxicity)
depending on
steel grade
Final Statement to metallic coating from chromium trioxide for dental and surgical
hand piece-applications:
For dental or surgical hand-piece applications there are no acceptable alternatives to metallic
plating from chromium trioxide. None of the alternatives would fulfill the technical
requirements of dental and surgical instruments.
For this reason, we also advocate for continued use of chromium trioxide for dental and
surgical instruments for “functional chromium plating with decorative character” and a further
review period of 7 years.
Chromium trioxide - Functional chrome plating with decorative character for dental and surgical instruments
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