PDF, Dental Alloys, History, Composition, Basic material properties, local & Systemic toxicity, Allergy, Mutagenicity & Teratogenicity, Public concerns & contravercy.

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BIOCOMPATABILITY OFBIOCOMPATABILITY OFBIOCOMPATABILITY OFBIOCOMPATABILITY OF
DENTAL ALLOYSDENTAL ALLOYSDENTAL ALLOYSDENTAL ALLOYS
Presented by:
Dr. Hashmat Gul
Demonstrator , NUST,
AMC,Dental Materials.
1. INTRODUCTION TO DENTAL1. INTRODUCTION TO DENTAL1. INTRODUCTION TO DENTAL1. INTRODUCTION TO DENTAL
ALLOYSALLOYSALLOYSALLOYS

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HistoryHistoryHistoryHistory
• More than 3,000 alloys are available for
dental applications.
• In the past 20 years, many studies about the biocompatibility of
dental alloys have been published.
• Still , it is impossible to list “good” or “bad” alloys for any given
application.
The Aim of this ChapterThe Aim of this ChapterThe Aim of this ChapterThe Aim of this Chapter
• Dental alloys exhibit long-term intimate
contact with vital tissue, i.e.
direct or indirect contact with epithelium,
connective tissue, or bone.
• To present fundamental principles that can serve as guidelines for
assessing the tissue compatibility of presently available alloys as
well as of new alloys.

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2. BASIC MATERIAL2. BASIC MATERIAL2. BASIC MATERIAL2. BASIC MATERIAL
PROPERTIESPROPERTIESPROPERTIESPROPERTIES
CompositionCompositionCompositionComposition
• An alloy is a mixture of two or more metals
or non-metals(elements).
• Dental alloys usually contain 4-8 different metals.
Thus, are metallurgically complex.
EVOLUTION OF ALLOY COMPOSITION
• In the past 20 yrs the increasing price of gold & palladium , lead to
evolution of Dental alloys.
• Today’s Dental alloys may be based on Ag, Au, Pa, Ni, Co, or Ti.

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Methods of Expressing Alloy CompositionMethods of Expressing Alloy CompositionMethods of Expressing Alloy CompositionMethods of Expressing Alloy Composition
Composition of Dental
Alloys
Percentage
Composition
Weight % Atomic %
Phase
Composition
The wt.% and at.% of an alloy may be substantially different from one another.
The differences between wt.% and at.% are greatest when large differences
exist among the atomic weights of the component elements
Composition inComposition inComposition inComposition in WtWtWtWt% & At% of% & At% of% & At% of% & At% of 3333 types of Dentaltypes of Dentaltypes of Dentaltypes of Dental
AlloysAlloysAlloysAlloys

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Composition by Phase StructureComposition by Phase StructureComposition by Phase StructureComposition by Phase Structure
Phases are areas within an alloy that have essentially the same
composition.
SINGLE PHASE ALLOY MULTIPLE PHASE ALLOY
Homogenous composition throughout their
structure..
Heterogeneous composition throughout its
structure.
The phase structure of an alloy is critical to
its corrosion properties and to its
biocompatibility.
The interaction between the biological
environment and the phase structure is what
determines the element released and the
body response to the alloy.
Biocompatibility of Dental AlloysBiocompatibility of Dental AlloysBiocompatibility of Dental AlloysBiocompatibility of Dental Alloys
• The complexity and diversity of today’s dental alloys make
understanding their biocompatibility difficult :
1. Any element in an alloy may be released & influence vital
tissue.
2. Insufficient data available on the biological properties of
many dental alloys.

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Corrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element Release
MECHANISM: The electrochemical corrosion of alloys involves the
ionization of elements that are released into the environment, e.g.,
saliva.
METHODS OF MEASURING CORROSION
• By observing the alloy for deterioration or discoloration of its
surface (e.g., tarnish)
• By Electrochemical testing
• By direct measurement of released elements (e.g., atomic
absorption spectroscopy, atomic emission spectroscopy)
Corrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element Release
THE BIOLOGICAL RESPONSE TO AN ALLOY DEPENDS ON
• The quantities released.
• The duration of tissue exposure to these elements.
• The biological effects of released elements,
• Toxicity,
•Allergy,
• Mutagenicity.
l

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Corrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element Release
FACTORS INFLUENCING THE CORROSION OF DENTAL ALLOYS & LABIALITY
(Element Release)
Composition of the alloy (particularly
at the surface)
Phase structure of the alloy
Surface structure (roughness, presence
of oxides)
Oral environmet
Thermal treatment/history
Combinations of alloys (gold coating,
soldering)
Time in service
CorrosionCorrosionCorrosionCorrosion & Element& Element& Element& Element ReleaseReleaseReleaseRelease---- FFFFACTORSACTORSACTORSACTORS INFLUENCING THE CORROSION OFINFLUENCING THE CORROSION OFINFLUENCING THE CORROSION OFINFLUENCING THE CORROSION OF
DENTALDENTALDENTALDENTAL ALLOYS & LABIALITYALLOYS & LABIALITYALLOYS & LABIALITYALLOYS & LABIALITY (Element Release)(Element Release)(Element Release)(Element Release)
----
COMPOSITION
Tendencies to be released
Cu, Ni & Zn > Au & Pd.
The electronic structure of
the elements at the atomic
level.
The effect of other
elements. e.g.,
In dental alloys, Pd can
reduce the labiality of Cu
PHASE STRUCTURE
Multiple phases in alloy
increases the risk of element
release from the alloys
because of the potential for
electrochemical corrosion
among the phases.
SURFACE STRUCTURE
Surface roughness tends to
increase elemental release.
Greater surface area of
exposure to the external
environment.
Creation of local
microenvironments that
vary the exposure of the
surface to oxygen.
Surface Oxides: The
formation of TiO2 on the
surface of Ti reduces the
labiality of titanium.

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Corrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element ReleaseCorrosion & Element Release---- FFFFACTORS INFLUENCING THE CORROSION OFACTORS INFLUENCING THE CORROSION OFACTORS INFLUENCING THE CORROSION OFACTORS INFLUENCING THE CORROSION OF
DENTAL ALLOYS &DENTAL ALLOYS &DENTAL ALLOYS &DENTAL ALLOYS & LABIALITY (Element Release)LABIALITY (Element Release)LABIALITY (Element Release)LABIALITY (Element Release)
ORAL ENVIRONMENT
REDUCED pH
significantly increases
the corrosion of some
alloys, particularly
those based on nickel.
LOCATION: Corrosion is
also particularly high in
crevices, gaps, and pits,
and in the gingival
sulcus.
THERMAL TREATMENT
FIRING OF A CERAMIC:
Metal oxides at the crown
margin, not covered by
ceramic may promote
elemental release
localized gingivitis
RECASTING OF BASE METAL
ALLOYS (50% old and 50%
new material)
increase the release of
elements and cytotoxicity.
SOLDERS may increase the
corrosion of dental alloys.
COMBINATION OF
ALLOYS
A GOLD SURFACE
COATING
of Ni-based or Co-based
alloys should be
discouraged.
May enhance
corrosion rather
than retard it.
The long-term
bonds not so
durable between
coatings and the
alloys.
TIME IN SERVICE
The release of
ions from alloys
may
Decrease with
the time.
Continue for
extended
periods.
CorrosionCorrosionCorrosionCorrosion & Element& Element& Element& Element ReleaseReleaseReleaseRelease
IMPLANTED DENTAL ALLOYS
1. All release elements into the adjacent
tissues.
2. Rate of element release
Titanium < Cobalt-base alloys < Nickel-base
alloys, or stainless steel.
3. At implantation site rate of element release
determine the tendency of metals to
accumulate locally. e.g in Implanted Ni-Cr
alloys, High conc. of Ni & Cr are found in the
adjacent soft tissues.
4. Systemic distribution of released elements
from local tissues not documented.
IMPLANTED DENTAL ALLOYS
4. Rate of excretion
Ti < Al < V
5. Ti and Ti-alloys usually release relatively
small amounts into the neighbouring
tissues.

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CorrosionCorrosionCorrosionCorrosion & Element Release& Element Release& Element Release& Element Release
NON-IMPLANTED DENTAL ALLOYS
5. Tooth brushing & acidic pH generally
increases the elemental release from nickel-
based alloys.
6. Salivary proteins form a metal–protein
complex on the surface of an alloy , which
can increase corrosion, particularly of Ni–Ti
alloys.
NON-IMPLANTED DENTAL ALLOYS
1. All release elements into the adjacent
tissues.
2. The reduced nobility can result in higher
amounts of elemental release. e.g., Cu, Cd,
Ni & Zn reveal a high corrosion tendency
(lability). But Ag, Au, Pd & Pt has a lower
lability.
3. Multiple-phase alloys release considerably
more mass, even in alloys with a high gold
content compared with single-phase alloys
of similar composition.
4. In a gold-based alloy , Pd may reduce the
corrosion tendency of Cu.
3.SYSTEMIC TOXICITY3.SYSTEMIC TOXICITY3.SYSTEMIC TOXICITY3.SYSTEMIC TOXICITY

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SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
The Oxidation state & Form of elements
influence its absorption, distribution,
systemic half-life , deposition &
excretion.
ABSORPTION
Dental Alloy
Elements
Released
In Oral Cavity
Through
Epithelium
Systemic
Circulation
Gut , Gingiva Lungs
In Bone around
the Implant
Systemic
Circulation
SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
ABSORPTION e.g.,
• The route of Administration of element is critical to its biological effects
e.g., In mice, Pd administration.
ORAL
Pd ions, LD50 of
1000mg/kg body
wt.
PERITONEUM
Pd ions, LD50 drops
to 87mg/kg body
wt.
INTRAVENOUS
Pd ions, LD50 is
much lower.

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SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
DISTRIBUTION
Once inside the body, the distribution of a metallic element mediates its
ability to cause systemic toxicity.
Diffusion through tissues
Lymphatic
Blood
stream
Ingested by
cells(Macrophages)
Lymphatic
Blood
stream
SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
DEPOSITION of Elements in body
Ultimately, metal ions are deposited to many tissues or organs,
each harboring its characteristic amount (deposition).
Ultimately, metal ions are deposited to many tissues or organs,
each harboring its characteristic amount (deposition).
Tissue affinity is unique for each metal & for each chemical form of
the metal.
Tissue affinity is unique for each metal & for each chemical form of
the metal.

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SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
EXCRETION 1. Ultimately, the body eliminates
these metals through the urine,
feces, or lungs.
2. The rate of elimination is also unique to each. e.g, if
palladium ions are given intravenously to rats, 20% of the
palladium will remain in the rats after 40 days. However, if Pd is
administered orally, only 1% will remain in the rats after 3 days.
3. The low apparent retention of orally administered palladium
is in large part a result of the low percentage of the palladium
that actually gets into the body tissues. Most of the palladium
is directly excreted.
FACTORS AFFECTING SYSTEMIC TOXICITYFACTORS AFFECTING SYSTEMIC TOXICITYFACTORS AFFECTING SYSTEMIC TOXICITYFACTORS AFFECTING SYSTEMIC TOXICITY
•A copper band used for an impression
The tissue’s exposure time to the alloy.
• Alloys subject to abrasion due to opposing occlusion
or restorations may release higher levels of elements.
The function of an alloy.
• Oral location
• bone implantation.
Location of an alloy & Corrosion resistance
• Bacteria, cells, or biologically active molecules
(glycoproteins) are bound to different alloy surfaces
can considerably influence tissue compatibility.
The surface adhesion properties of an alloy.

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SYSTEMICSYSTEMICSYSTEMICSYSTEMIC TOXICITYTOXICITYTOXICITYTOXICITY
IMPLANTED DENTAL ALLOYS
Systemic distribution of Elements
Orthopedic implants exhibited.
Dental implants nil/traces.
For cobalt-chromium and stainless steel ,
the released elements are distributed systemically .
In titanium-based implants, the released metal
ions cause little/no systemic toxicity.
The risk–benefit ratio,
benefits of titanium-based implanted dental alloys >
risks of Systemic toxicity.
NON-IMPLANTED DENTAL ALLOYS
Exhibit no systemic toxicity.
It must be stressed that release of mass from an alloy
that approaches dietary levels does not predict
systemic toxicity or other effects from the alloy
Inhalation of metal dusts generated by the
finishing and polishing of alloy restorations lead to an
elevated risk of LUNG FIBROSIS.
Beryllium dust most dangerous
Cobalt–chromium dust
Asbestos dust
Ceramic dust
The use of beryllium in dental alloys is no longer
recommended
SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITY
Complaints & its Management
To determine the cause of nonspecific symptoms requires intense collaboration of the
dental practitioner with general physicians and psychiatrists.
Dental alloy restoration
Adverse Symptoms
A Careful Oral examination
A Comprehensive Medical
history
Concurrent systemic
diseases.
drugs the patient may be
taking

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4. LOCAL TOXICITY & TISSUE4. LOCAL TOXICITY & TISSUE4. LOCAL TOXICITY & TISSUE4. LOCAL TOXICITY & TISSUE
COMPATABILITYCOMPATABILITYCOMPATABILITYCOMPATABILITY
LOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITY
IMPLANTED DENTAL ALLOYS
Tissue necrosis and inflammation caused by
metals including pure copper, nickel, zinc, and
aluminium and alloys such as brass.
Failure of osteo-integeration occur in Ni-based
and Co-based alloys , even though no severe necrosis
or inflammation occurs around the implants.
A low release of elements is a necessary but
not a sufficient condition for Osseo-
integeration. e.g. Ti & Ti-alloys
Other factors effecting Osseo-integration
include:
Surface Oxide formation
Attachment of osteoblasts
The protein layer that adheres to the
implant surface.
Material properties like Charge effect.
NON-IMPLANTED DENTAL
ALLOYS
Corrosion & Local Toxicity: Dental alloys are in
long-term intimate contact with local tissues, and
“microenvironments” are often formed between
the alloy and the tissues leading to corrosion &
local toxicity e.g. Crevice corrosion occurs
In dental crown extending into the
gingival sulcus.
Beneath the metal framework of a
removable partial denture.
The local biological effects of these elements are
still debatable.

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METAL IONS TOXICITY AT CELLULAR LEVELMETAL IONS TOXICITY AT CELLULAR LEVELMETAL IONS TOXICITY AT CELLULAR LEVELMETAL IONS TOXICITY AT CELLULAR LEVEL
Metal ions Affect cellular functions , such as
osteoclast function ,
the function of cellular mitochondria ,
cytokine release ,
the activity of transcription factors,
the synthesis of glutathione ,
the structure of the cytoskeleton.
Amplify cellular responses to inflammatory activators such as lipopolysaccharide (LPS).
At sufficiently high concentrations, metal ions alter Cellular metabolism Cell death.
The toxicity of these metal ions is reported as the concentration to depress cellular
activity by 50%, or the toxic concentration 50% (TC50 value).
Prolong exposure of cells to metal ions the TC50 value of metal ions decreases.
Various metal ions may interact , causing an increase or decrease in cytotoxicity.
Below toxic concentrations, exhibit Apoptosis Cellular necrosis ( e.g. Cr , Ni & Co ).
METAL ION TOXICITY INMETAL ION TOXICITY INMETAL ION TOXICITY INMETAL ION TOXICITY IN
CELL CULTURESCELL CULTURESCELL CULTURESCELL CULTURES
CELL CULTURES-in vitro tests
PROBLEMS ENCOUNTERED
Only short-term exposures of alloys are used in most in-vitro tests, in contrast to many years
of exposure in-vivo.
In-vitro tests will not cover interactions between various cell types, which is a frequent feature
of biological reactions in vivo. However, these tests can evaluate the general biological
characteristics of materials.
BEHAVOUR OF DENTAL ALLOYS IN CELL CULTURES
Multiple-phase alloys, are more cytotoxic than similar single-phase alloys.
Ceramic alloys may be more cytotoxic after thermal treatment gingivitis adjacent to
crowns.
An alloy–solder combination, toxicity cannot be theoretically deduced from the toxicity of the
individual alloy.

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Fig.Fig.Fig.Fig. Typical doseTypical doseTypical doseTypical dose----response curveresponse curveresponse curveresponse curve....
The activity of mitochondria was
measured after a 24-h treatment
with different silver ion
concentrations.
The TC50 value according to this
graph is 6 μM.
The control cultures were not
incubated with silver .
Fig.Fig.Fig.Fig. Influence of exposure time onInfluence of exposure time onInfluence of exposure time onInfluence of exposure time on
the TC50the TC50the TC50the TC50 value (withvalue (withvalue (withvalue (with Cu ions).Cu ions).Cu ions).Cu ions).
More copper is needed after short-
term exposure to inhibit cell growth
by 50% compared with longer
exposure periods.

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METALMETALMETALMETAL IONS & BACTERIAL ADHESIONIONS & BACTERIAL ADHESIONIONS & BACTERIAL ADHESIONIONS & BACTERIAL ADHESION
BACTERIAL ADHESION-in vitro tests
PLAQUE is the primary cause of gingivitis and periodontitis(in addition to other factors).
A decreased pH underneath plaque may increase corrosion of some alloys, particularly those
based on Ni & Co.
A high surface energy and a rough surface structure promote bacterial adhesion. e.g. Certain
bacteria adhered better to a titanium alloy than to commercially pure titanium.
THE PELLICLE reduces bacterial adhesion independent of the material’s free surface energy.
SALIVA generally reduces microbial adhesion.
ALLOYS CONTAINING Cu AND Ag showed stronger antimicrobial effects in vitro than metals
used for denture bases.
METALMETALMETALMETAL IONS & IMPLANTATION TESTSIONS & IMPLANTATION TESTSIONS & IMPLANTATION TESTSIONS & IMPLANTATION TESTS
IMPLANTATION TESTS-in vivo tests
CHALLENGES
Difficult to replicate a clinical alloy-tissue interface in an animal model.
Implantation tests do not simulate the extra-epithelial application of dental alloys.
Shape, size, and surface characteristics of an alloy may influence the subsequent
biological reaction.
Intraoral conditions (chewing, brushing, plaque, vicinity to other alloys) are not
accounted for in most implantation tests in animals.

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LOCAL CLINICAL SYMPTOMS & COMPLAINTSLOCAL CLINICAL SYMPTOMS & COMPLAINTSLOCAL CLINICAL SYMPTOMS & COMPLAINTSLOCAL CLINICAL SYMPTOMS & COMPLAINTS
COMPLAINTS FREQUENCY CAUSES
Gingivitis 28 Ni & Cu Based alloys.
High gold & Gold-reduced alloys
Surface oxide layer on Ceramic alloys.
Tooth-ache 20
Fissured/Geographic tongue 16
Increased salivary flow 13
Palatal erythema underneath a
metal base
9 toxic/ allergic in nature
Insufficient fit of denture
Infection :Bacterial/Fungal
Lichenoid reactions Sharp-edge, Toxic-irritant, allergenic reaction
Amalgam
Resin-based Composites
Dental alloys
5. ALLERGIES5. ALLERGIES5. ALLERGIES5. ALLERGIES----MECHANISMSMECHANISMSMECHANISMSMECHANISMS
Metal ions act as
Haptens
Metal ions act as
Haptens
Bind to resident
molecules
Bind to resident
molecules Allergic reactionAllergic reaction
Foreign-body
response
Foreign-body
response
Alter the
molecular
structure
Alter the
molecular
structure
Allergic reaction to an alloy is not possible unless an ELEMENT IS RELEASED from the alloy.
E.g. Some individuals exhibit allergic reaction to Palladium ions but no reaction to
Palladium metal because few ions are released.
Oral exposure has been reported to cause TOLERANCE (e.g., to nickel) .
A CROSS-ALLERGY: when antigens are sufficiently similar that allergy to one antigen will
guarantee allergy to the second antigen even with no previous exposure. E.g.
Patients who are sensitive to Pd are nearly always allergic to Ni.
The incidence of documented allergies to Pd-containing dental alloys is less than to
Ni-containing alloys. This incidence is further decreased by the relatively low corrosion
rate of palladium alloys. Still, this possibility should be discussed with the patient

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ALLERGIES & ALLOYSALLERGIES & ALLOYSALLERGIES & ALLOYSALLERGIES & ALLOYS
DIAGNOSIS
•Patch test
•Skin prick test
FACTORS AFFECTING ALLERGY DIAGNOSIS
•Method of Diagnosis
•Type of metal salt
•Oxidation state of metal.
•Nature of Vehicle used.
CLINICAL SYMPTOMS
Local Oral Allergic Symptoms Extra-Oral Allergic
Manifestations
Oral Lichenoid Reaction
Local Gingivitis/Stomatitis
Contact Dermatitis
Urticaria on abdomen & limbs
Peri-oral allergic reaction.
ALLERGIESALLERGIESALLERGIESALLERGIES
Palatal Erythema due to Gold-plated
metal base.
Lichenoid reaction of mucosa
contacting an alloy
Peri-Oral Allergic
reaction to Ni-containing
Orthodontic wire
Urticaria

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ALLERGIESALLERGIESALLERGIESALLERGIES---- FrequencyFrequencyFrequencyFrequency ofofofof Allergies to MetalAllergies to MetalAllergies to MetalAllergies to Metal IonsIonsIonsIons
CURRENT STUDIES
Element Allergy
Documentation in
Patch test
General Population
Sensitivity
Gold 23%
Nickel 28% 15%
Cobalt 14% 8%
Palladium 9%
Mercury 6%
Chromium 8%
6. MUTAGENICITY,6. MUTAGENICITY,6. MUTAGENICITY,6. MUTAGENICITY,
CARCINOGENICITY,CARCINOGENICITY,CARCINOGENICITY,CARCINOGENICITY,
& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.

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MUTAGENICITY, CARCINOGENICITY,MUTAGENICITY, CARCINOGENICITY,MUTAGENICITY, CARCINOGENICITY,MUTAGENICITY, CARCINOGENICITY,
& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.
MUTAGENICITY CAN BE MEASURED
• in bacterial systems (e.g., Ames test)
• in mammalian cells (e.g., micronucleus test)
• Currently, limited reliability of these in vitro systems in predicting in vivo mutagenesis.
• No or little information available regarding mutagenicity in Dental alloys.
• Most evidence about the mutagenic activity of metallic elements has come from
industrial workers exposed to metallic compounds for years showing increased
incidence of neoplasia.
• In dental laboratories, the vapor form of elements such as beryllium is a common
mutagenic threat.
MUTAGENICITYMUTAGENICITYMUTAGENICITYMUTAGENICITY, CARCINOGENICITY,, CARCINOGENICITY,, CARCINOGENICITY,, CARCINOGENICITY,
& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.& TERATOGENICITY.
FACTORS AFFECTING MUTAGENICITY
• Route of Exposure.
• Oxidation state of Element e.g. ( Cr3 non-mutagenic , Cr6 mutagenic )
• Molecular form of metal e.g. Nickel ions non-mutagenic , nickel subsulfide mutagenic.
EXAMPLES OF COMMONLY USED ELEMENTS
IN DENTAL ALLOYS WITH
MUTAGENIC/CARCINOGENIC POTENTIAL
MUTAGENS CARCINOGENS
Beryllium
Cadmium
Chromium
Cobalt
Copper
Iron
Tin
Palladium
Beryllium
Cadmium
Chromium
Cobalt
Nickel

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7.7.7.7. PUBLIC CONCERNS &PUBLIC CONCERNS &PUBLIC CONCERNS &PUBLIC CONCERNS &
CONTROVERSIESCONTROVERSIESCONTROVERSIESCONTROVERSIES
PUBLIC CONCERNS & CONTROVERSIESPUBLIC CONCERNS & CONTROVERSIESPUBLIC CONCERNS & CONTROVERSIESPUBLIC CONCERNS & CONTROVERSIES
• In recent years, palladium and, to a lesser extent, nickel were frequently
viewed as harmful when used in dental alloys.
• Interestingly, a number of subjects who object to these dental alloys have
their tongues pierced without asking about the composition of the jewelry
used in the piercing alloy.

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PALLADIUM IN DENTAL ALLOYSPALLADIUM IN DENTAL ALLOYSPALLADIUM IN DENTAL ALLOYSPALLADIUM IN DENTAL ALLOYS
• (Pd2+), palladium ions can cause toxicity only at high concentrations.
• In dental alloys, palladium is among the least toxic of the metal
ions.
• Palladium dental alloys safe the low rate of Pd release .
• Palladium ions are also capable (as haptens) of causing hypersensitivity
reactions in the mouth. In most cases, these hypersensitivity reactions
occur in people with nickel hypersensitivity. Thus, a cross-allergy between
nickel and palladium is suspected.
• Palladium ions has a “slight” carcinogenic potential.
NICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYS
• The nickel content of some dental alloys is greater than 70 wt.% and nickel-
containing alloys are used in removable partial dentures, crowns, orthodontic
appliances, and endodontic files.
• Like Pd ions, Ni ions have documented adverse biological effects if present in
sufficient concentrations.
• Ni, is a well-documented allergen.
• Ni, is also carcinogenic, especially in nickel subsulfide (Ni2S3) form.
• Ni, ions cause a potent and persistent inflammatory response in connective
tissues. This inflammatory response is not allergically mediated.

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NICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYSNICKEL IN DENTAL ALLOYS
• The risk of using Ni-alloys is > Pd-alloys , because the ions that mediate
adverse biological responses are released in potentially large amounts.
• For orthodontic wires or endodontic files these alloys are the best alloys
currently available.
• However, the risks associated with nickel-containing alloys are higher than for
other dental alloys. Thus, the risk–benefit ratio is somewhat less favorable
for these alloys.