amalgam safety

7/28/2019 Amalgam Safety

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Amalgam Safety

Overview

• History of amalgam

• Mercury exposure

• Forms of mercury

• Amalgam concerns

• Alternative materials• Summary

Amalgam

• An alloy of mercury with another metal.

Click here for slide presentation on amalgam

Debut of Amalgam

• Introduced in 1800’s in France

– alloy of bismuth, lead, tin

and mercury – plasticized at 100 ºC

– poured directly into cavity

• 1826 - Traveau

– compounded a silver paste amalgam• mixture of silver shavings from coins and mercury

– condensed into tooth at room temperature

Mackert JADA 1991

Amalgam War I

• 1833 - Crawcour brothers

– heavily marketed their amalgam

of silver and mercury

• 1843 - American Society of Dental Surgeons

– declared use of amalgam malpractice

• mercury is a poison

– threatened to expel users• Amalgam use declined

Mackert JADA 1991

Amalgam War I

• 1895 - G.V. Black

– developed effective amalgam

• improved handling and performance

• similar to contemporary low-copper

amalgam

• Popularity of amalgam increased – failure of adverse health effects to

materialize

Black Dent Cosmos 1896

Amalgam War II

• 1924 - Alfred Stock

– German professor of chemistry

– became poisoned with mercury

• 25 years of laboratory research

– published papers on the dangers of

mercury in dentistry• Created considerable public concern

Stock Med Klin 1296

Amalgam War II

• 1934 - German physicians

– studied patients

• occupationally exposed to mercury – with and without amalgams

– published papers

• no health risk from amalgams

• 1941 - Stock recanted his position

Mackert JADA 1991

Amalgam War III

• 1970 - 1990

– concern over occupational

exposure of mercury vapor to dentists

– excess levels in 10% of dental offices• > threshold limit of 50 ug/mm3

– urinary mercury levels high• mild functional effects found

– ADA institutes mercury hygiene campaign

Mandel JADA 1991

Amalgam War III

• 1970 - 1990 – urinary mercury levels

lowered 50 %

– a shift in concerns• from occupational risk to

dentists to patient risk

– ability to measure mercury

release from amalgamrestorations in expired air

• early tests grosslyoverestimated

Mandel JADA 1991

Naleway J Pub Healt Dent 1991

1980 1986 1991

Urinary Mercury Levels inDentist

Anti-Amalgamists

• Dentists specialize in treating purportedmercury toxicity – becomes a marketing tool

• Hal Huggins – publications, videotapes

and seminars

– removal of amalgam purportedly cures• Leukemia

• Hodgkin’s disease • Multiple Sclerosis

– website: Hugnet

The Amalgam Scare Campaign

Evidence-Based Care

• Critically evaluating researchliterature and clinical data – lay population unfamiliar with

peer-reviewed dental literature – rely on media stories and internet

• Survey by ADA in 1991 – 1000 adults

• nearly 50% believed health problems possible fromdental amalgams

– click here for details

Guyatt JAMA 1993

Dodes JADA 2001

Why Amalgam?

• Inexpensive

• Ease of use

• Proven track record

– >100 years

• Familiarity

• Resin-free

– less allergies than composite

Ten Clinical and Legal Myths of Anti-Amalgam

Amalgamation

• Alloy (Ag-Sn-Cu) mixed with

approximately 50% mercury (Hg)

– within several hours,no free mercury remains

• stable intermetallic compounds

Ag-Sn-Cu + Hg Ag-Sn-Cu + AgHg + Cu-Sn alloy undissolved

alloymatrix copper

Liquid Mercury

• Hydrargyrum (Hg)

• Activates amalgamation reaction

• Only pure metal that is liquidat room temperature

Click here for ADA Mercury Hygiene Recommendations

Amalgam Restorations

• Half-billion restorations per year

– 75 tons of mercury

• Mercury vapor released

– chewing and brushing• Berglund J Dent Res 1990

– removal of amalgam• reduced 90% with high-volume evacuation

– Pohl Acta Odontol Scand 1995

– difficult to determine vapor levelsaccurately

• Olsson J Dent Res 1992

Mercury Dose from Amalgam

• Average daily dose from 8 – 10 amalgamsurfaces

– 1-2 ug per day – well below threshold levels

• Threshold urine mercury levels

– subtle, pre-clinical effects• 30 ug per day

– considered dangerous• 82 ug per day Olsson J Dent Res 1995

Mackert Crit Rev Oral Biol Med

1997 Berdouses J Dent Res 1995

Exposure to Mercury

• Food

– fish, grain

• Air, water – naturally occurring

• Commercial products

– antiseptics

– ointments

– thermometers

• Occupational

– dentistry

– factory workers

Sources of Mercury

• Anthropogenic

– fossil fuels• coal

– industrial processes• waste incineration

• boilers

– products

• fluorescent lamps

• batteries

• thermometers

• amalgam

Fate and Transport of Mercury

• Continuously mobilized, deposited andremobilized – atmosphere

• global circulation – transferred to surface

» wet or dry deposition

– terrestrial• soil deposition

– aquatic• may enter food chain

– concentrates in fish

» greatest source of human exposure

www.epa.gov/mercury/exposure.htm

Forms of Mercury

• Elemental

• Inorganic

• Organic

Osborne J Esthet Rest Dent 2004

Elemental Mercury

• Un-ionized mercury

• High vapor pressure

– significant to dentistry• Absorption

– readily from lungs

– poorly from GI and skin• < 0.1%

• not toxic when swallowed

Clarkson Crit Rev Clin Lab Sci 1987

Mercury Vapor

• Accounts for most occupational andhome exposures

– mercury spills• thermometers

• fluorescent light bulbs

• Significant toxicity when

inhaled – 80% absorbed by lungs

• Acute toxicity is rare

Hursh Arch Environ Health 1976

Inorganic Mercury

• Highly toxic as inorganic salts• Hg2+ mercuric ion

– mercuric oxide

• swallowed batteries by children – mercuric sulfide

• red tattoos

• Hg1+ mercurous ion

– mercurous chloride• laxatives

• teething powder Wands Am J Med 1974 Litovitz

Pediatrics 1992

Organic Mercury

• Alkyl – methyl - most toxic form

• 95% absorbed in gut

• responsible for several masspoisonings

– Minamata Bay, Japan - 1950» inorganic mercury dumped in bay

» methylated by aquatic organisms

» concentrates up food chain

– ethyl – preservative

• Thimerosal – anti-microbial in pharmaceuticals

• Aryl – highly toxic – antifungal on seeds

Renzoni Environ Res 1998

Mercury Monitoring

• Exhalation

– difficult to perform reliably

• Urine – best method for chronic

exposure

• symptoms – 300 ug/L• normal < 25 ug/L

Goldfrank’s Toxicologic Emergencies 1990

Mercury Monitoring

• Blood

– normal < 6 ug/L

– reflects recent exposure• 3-day half-life

– reliable measurement of methylmercury

exposure• Hair

– not a reliable method

WHO Environmental Health Criteria

Biologic Activity of Mercury

• Binds to protein sulfhydryl groups

– loses structure and function

• No carcinogenicity• Teratogenicity

Symptoms of Toxicity

• Acute high-level

exposure

– hypersalivation – cough

– dyspnea

– bronchitis

– Pneumonia – vomiting

– gastroenteritis

• Chronic low-level

exposure

– depression – irritability

– weakness

– tremor

– insomnia – renal failure

– memory loss

Concerns with Amalgam

• Dental occupational exposure

• Amalgam waste

• Hypersensitivity• Mercury accumulation

• Multiple sclerosis

• Alzheimer’s disease

• Renal toxicity

• Reduced immunocompetence

• Amalgam illnessTen Medical Myths of Anti-Amalgam

Dental Occupational Exposure

• Poor mercury hygiene

– in-office dispensing

• mercury and alloy powder

– mercury spills

– use of squeeze cloths

– inadequate suction and water spray duringamalgam removal

Minimizing Office Exposure

• Pre-capsulated amalgam

• Store scrap amalgam in tightly-closedunbreakable container

– recap capsules

• Water spray and high-volume evacuationwhen polishing or removing amalgam

• Close cover on triturator when in use

• Use care when handling amalgam – avoid skin contact

Click here for slide presentation on Mercury Hygiene

Click here for ADA Mercury Hygiene Recommendations

Amalgam Waste

52%34%

13% <1%

Fuel CombustionWaste Combustion

Manufacturers

Dentistry

• Mercury is a naturally occurring metal

• Half of environmental mercury comes

from human activity

– < 1% dentistry

Wastewater Discharge

• Primary source of mercury in water is air

• However, increased regulatory pressure

to control mercury in wastewater

• Dental offices become easy

identifiable source

• Municipal water treatment authorities

– attempt to regulate mercury wastewater fromdental offices

Click here for ADA Summary of Amalgam in Wastewater

Click here for ADA Best Management Practices for Amalgam Waste

Amalgam Waste

• Non-contact amalgam

– store in sealed container

• Contact amalgam

– disinfect and dry

• non-chlorine disinfectant

– combine with non-contact amalgam

• Used amalgam capsules – recap, if possible

Click here for USAF Best Management Practices for Amalgam Waste

Click here for slide presentation on Mercury Hygiene

Amalgam Waste

• Extracted teeth

– disinfect and dry

• non-chlorine disinfectant

• Chairside traps

– disinfect and dry – store with used

amalgam capsules

Amalgam Restrictions

• Typically to reduce the amount

and sources of mercury by

various countries

– in the environment

– exposure to children and

pregnant women

• Examples

– Belgium, Denmark, Finland, Sweden

Rowland Occup Environ Med 1994

Hypersensitivity

• Type IV or cell-mediated immune response

• Contact dermatitis

• Lichenoid lesions adjacent toamalgam

• Most reactions subside

– amalgam removal usually not necessary

• True allergy is rare

– < 1%

Anneroth Acta Odontol Scand 1992

Duxbury Br Dent J 1982

McGiven Br Dent J 2000

Hypersensitivity

• Double-blind study

– 660 subjects

– tested with 1% ammoniatedmercury

– 3% positive skin response

• only 20% of these had true allergy (0.6%)

Storrs J Am Acad Dermatol 1989

Mercury Accumulation

• Studies found higher mercury levels invarious organs – in sheep and monkeys with

amalgam placement – Hahn FASEB 1989, 1990

• critical review of studies

– Eley Br Dent J 1997

» probable result of swallowedscrap amalgam

» no controls

– in dental staff • Nylander Swed Dent J 1989

Renal Toxicity

• Study evaluating kidney function

– Boyd AM J Physiol 1991

• 6 sheep with 12 amalgams

• 2 sheep with glass ionomers (control)

• reported 60% loss of renal function

compared to control

– study reviewed by renal physiologists

• Malvin Am J Physiol 1992 – poor model

– data support improved renal function

Renal Toxicity

• Studies showing no renal dysfunction due to

amalgam restorations

– Molin Acta Odontol Scand 1990

– Sandborgh-Englund Am J Physiol 1996

– Herrstrom Arch Environ Health 1995

– Naleway J Public Health 1991

– Langworth J Dent Res 1997

Reduced Immunocompetence

• Study showing drop in lymphocyte levelwith amalgam placement – Eggleston J Prosthet Dent 1983

• baseline CBC on 2 patients

– placed amalgams and new CBC

– removed amalgams and new CBC

• However, change was consistent

with normal diurnal variation in cellcounts and measuring error – Mackert JADA 1991

Reduced Immunocompetence

• Studies show no damage to immune

system from amalgam restorations

– Herrstrom Scand J Prim Health Care 1994

– Loftenius J Toxicol Environ Health 1998

– Herrstrom Arch Environ Health 1994

– Mackert JADA 1991

Amalgam Illness

• Multitude of conditions reportedly caused bythe presence of amalgam – symptoms may be due to mental disorders

• Studies found reduction of symptoms after amalgam removal – 70% of patients reported reduction

• Siblerud J Orthomol Med 1990

– patients reported 88% reduction• Lichtenberg J Orthomol Med 1993

• Critics site lack of control groups, poor studydesign, and placebo effect

• Wahl Quintessence Int 2001

Major Health Organizations

• Alzheimer’s Association “…no connection between Alzheimer’s and mercury-containing

dental fillings…”

• National MS Society

“There is no scientific evidence to connect the development of MS or other neurological diseases with dental fillingscontaining mercury.”

• Food and Drug Administration (FDA) “…no valid scientific evidence has ever shown that amalgams

cause harm to patients with dental restorations.“ • American Dental Association

“Dental amalgam (silver filling) is considered a safe, affordableand durable material…”

Alternative Materials

• Typically higher cost and/or greater

technique sensitivity

– composite resin – glass ionomer

– ceramic

– metal alloys

How Dental Materials Compare

Comparison of Toxic Effects

Amalgam Composite Glass Ionomers

Systemic Toxicity

- acute

- chronic

None None None

Not verified Not verified Not verified

Allergic Reactions Rare Rare, but many

components have

allergic potential

Extremely rare

Anaphylaxis None so far Isolated cases None so far

Cytotoxicity Low Slight to high Slight to high

Mutagenicity or

Carcinogenicity

None Certain components

mutagenic in vitro

Slight mutagenicity

Lichenoid reactions Yes Yes None

WHO 1997

Risk vs. Benefit Relationship

• Benefits and detriments to

the use of any material

• Unbalanced risk assessmentsmay lead to the waste of

limited health resources

– deny public access to beneficial therapies

ADA Council on Scientific Affairs JADA 1998

Corbin JADA 1994

Survey of Practice Types

Civilian General Dentists

32% Amalgam

AmalgamFree

Haj-Ali Gen Dent 2005

Frequency of Posterior Materials

Frequency of Posterior Materialsby Practice Type

Amalgam Direct Composite Indirect Composite Other

Amalgam Users

Amalgam Free

Haj-Ali Gen Dent 2005

Profile of Amalgam UsersCivilian Practitioners

Do you use amalgam in

your practice?

DPR 2005

Do you place fewer amalgams

than 5 years ago?

R i f Cli i l St di

Review of Clinical Studies(Failure Rates in Posterior Permanent Teeth)

Amalgam Direct

Inlays

Ceramic

Inlays

CAD/CAM

Inlays

Inlays &

Onlays

Longitudinal Cross-Sectional

Hickel J Adhes Dent 2001

% Annual Failure

R i f Cli i l St di

A m a l g

D i r e c t C o

C o m p o m e r

C o m p I n l a

C e r a m i c I n l a

C A D /

C a s t G o l d G I

T u n n e l A R T

% Annual Failure

Manhart Oper Dent 2004

Click here for abstract

Standard Deviation

Longitudinal and Cross-Sectional Data

Review of Clinical Studies(Failure Rates in Posterior Permanent Teeth)

Summary

• Dental amalgam

– releases minute amounts of elemental

mercury

• no evidence of systemic health problems

– limited cases of allergy

• Mercury absorbed from many sources

– no demonstration of clinical effects fromadditional burden from amalgam

Click here for Talking Paper on Amalgam Safety (PDF)

Summary

• No cure or health benefit from amalgamremoval

• Dentists must inform patients

– risks and benefits of restorative materials

• Research needed on specific healtheffects of low-level mercury exposure

– determine effects of amalgam-derivedmercury• need large-scale human studies

Click here for Talking Paper on Amalgam Safety (PDF)

Summary

• Materials research

– alternatives to amalgam

– reduce mercury emission from amalgams

• Amalgam will eventually be replaced by

composite and other materials

– esthetics

– environment

Online Fact Sheets

• Dental Amalgam Use and Benefits U.S. Centers for Disease Control Resource

Library Fact Sheet, December 2001; Accessed

Nov 2005

• California Dental Materials Fact Sheet

Accessed Nov 2005

Online Video• FDA Confirms Safety of Amalgam

Accessed Nov 2005

Online References

Dental Amalgam: A Scientific Review andRecommended Public Health Strategy for Research,Education and Regulation US Public Health Service1993; Accessed Nov 2005

American Academy of Pediatrics Web site

Accessed Nov 2005

Dental Amalgam: Update on Safety ConcernsJADA 1998; 129:494-501; Accessed Nov 2005

Dental Watch Website

Accessed Nov 2005

Acknowledgements

• Dr. David Charlton• Dr. Walt Thomas

• Dr. John Osborne

Questions/Comments

Col Kraig Vandewalle – DSN 792-7670

– ksvandewalle@nidbr.med.navy.mil

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