Biocompatability of dental alloys

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BIOCOMPATABILITY OF BIOCOMPATABILITY OF BIOCOMPATABILITY OF BIOCOMPATABILITY OF DENTAL ALLOYSDENTAL ALLOYSDENTAL ALLOYSDENTAL ALLOYS

Presented by:

Dr. Hashmat Gul

Demonstrator , NUST,

AMC,Dental Materials.

1. INTRODUCTION TO DENTAL 1. INTRODUCTION TO DENTAL 1. INTRODUCTION TO DENTAL 1. 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 MATERIAL 2. BASIC MATERIAL 2. BASIC MATERIAL 2. 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 CompositionComposition 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 in Composition in Composition in Composition in WtWtWtWt% & At% of % & At% of % & At% of % & At% of 3333 types of Dental types of Dental types of Dental types 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 ReleaseMECHANISM: 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 ReleaseTHE 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 ReleaseFACTORS 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

Corrosion Corrosion Corrosion Corrosion & Element & Element & Element & Element ReleaseReleaseReleaseRelease---- FFFFACTORS ACTORS ACTORS ACTORS INFLUENCING THE CORROSION OF INFLUENCING THE CORROSION OF INFLUENCING THE CORROSION OF INFLUENCING THE CORROSION OF

DENTAL DENTAL DENTAL DENTAL ALLOYS & LABIALITY ALLOYS & LABIALITY ALLOYS & LABIALITY ALLOYS & 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 OF ACTORS INFLUENCING THE CORROSION OF ACTORS INFLUENCING THE CORROSION OF ACTORS 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.

Corrosion Corrosion Corrosion Corrosion & 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.


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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Corrosion Corrosion Corrosion Corrosion & 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.


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 TOXICITYThe 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.

OR

AL

Pd ions, LD50 of 1000mg/kg body wt.

PE

RIT

ON

EU

M Pd ions, LD50 drops to 87mg/kg body wt.

INT

RA

VE

NO

US

Pd ions, LD50 is much lower.

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SYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYSYSTEMIC TOXICITYDISTRIBUTION

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 TOXICITYDEPOSITION 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 TOXICITYEXCRETION 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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SYSTEMIC SYSTEMIC SYSTEMIC SYSTEMIC TOXICITYTOXICITYTOXICITYTOXICITY


� 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.


� 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 TOXICITYComplaints & 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 examinationA Comprehensive Medical

history

Concurrent systemic diseases.

drugs the patient may be taking

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4. LOCAL TOXICITY & TISSUE 4. LOCAL TOXICITY & TISSUE 4. LOCAL TOXICITY & TISSUE 4. LOCAL TOXICITY & TISSUE COMPATABILITYCOMPATABILITYCOMPATABILITYCOMPATABILITY

LOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITYLOCAL TOXICITY & TISSUE COMPATABILITY


� 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 IN METAL ION TOXICITY IN METAL ION TOXICITY IN METAL 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 on Influence of exposure time on Influence of exposure time on Influence of exposure time on

the TC50 the TC50 the TC50 the TC50 value (with value (with value (with value (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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METAL METAL METAL METAL 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.

METAL METAL METAL METAL 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 & COMPLAINTSCOMPLAINTS 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---- Frequency Frequency Frequency Frequency of of of of Allergies to Metal Allergies to Metal Allergies to Metal Allergies 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.

Biocompatability of dental alloys

Health & Medicine

Transcript of Biocompatability of dental alloys