1. Amalgam Safety & Mercury Hazards (1-2010)
BY: Prof. Mostafa Abdulhamid Hassan
Mercury
One of the few metals that is liquid at room temperature
Used in medicinal preparations for more than 2000 years
Diuretics, laxatives, skin preparations
Used in over 60 industrial applications: Chlorine production,
insecticides, neon lights, paint, etc.
Mercury Uses
Thermometers
Electric Switches
Fluorescent Lamps
Batteries
Insecticides
Rat poisons
Disinfectants
Dental Amalgam
Physical Properties of Mercury :
Melting Point -38°C
Boiling Point 356°C
Density 13.5 gm/ml
Low heat of vaporization allows oxide-free metallic Hg to
evaporate easily at room temperature
Forms of Mercury
Metallic - Hg - Stable/Unreactive
Ionic - Hg+ - Reactive/Not a HazMat
Salts - HgCl - Mercuric Chloride
Compounds - Amalgam
Methyl Hg - Reacted Toxic Form/Poison
Vapor - Detectable?
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2. Mercury is present in the environment and it is taken into the body in
one form or another via water, air and food on daily basis
Scientific Facts
High levels of Hg do produce toxic effects
Hg vapor is minute/undetectable
Blood Hg increases upon removal of amalgam
Dental personnel have greatest exposure without evidence of
decreased health
True hypersensitivity to amalgam = allergic reactions or lichenoid
lesions
Sources of Mercury Exposure in Dental Office
Amalgam raw materials stored for use.
Mixed, unhardened amalgam during trituration and insertion.
Amalgam scrap
Amalgam undergoing F & P
Amalgam being removed
Mercury leakage of amalgam capsules
N.B : Once the amalgamation reaction is completed , only extremely
minute levels of mercury can be released and those are far below the
current health standard .
Historical Issues
First Amalgam War 1985 Huggins DDS “It’s All In Your Head”
1990 60 minutes Program “Poison In Your Mouth”
Anti-amalgamists
The Hazards From Mercury in Dentistry is Mainly Three Folded :
1. Systemic absorption of mercury through direct contact wit skin
2. Inhalation of mercury vapor given off at room temperature
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3. 3. Inhalation of air borne particles of mercury contaminated
particles
Anti-amalgam Claims
 Neurotoxicity
 Renal Dysfunction
 Birth Defects
 Arthritis
 Multiple Sclerosis
 Chronic Fatigue
 Etc , Etc , Etc…
Others Add Too !!
 Candida Infection
 Hodgkin’s Disease
 Mononucleosis
 Depression
 Ulcers
 Epilepsy
 Etc, Etc, Etc...
Adverse Reaction to Mercury Toxicity
Sensitization (hypersensitivity)
Mercurialism (Symptoms)
Symptoms of Mercury Toxicity
Insomnia
Physical weakness
Irritability
Loss of memory
Impaired vision
Nervous excitability
Headaches
Depression
Speech disorders
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4. Muscular tremors
Threshold Limit Value ( TLV ) for Mercury Vapor is 0.05 mg (50 µg/m3)
This concentration of mercury vapor represents the maximum level of
mercury vapor in which a person can work for 40 h/week without
demonstrable health risks.
Mercury Toxicity
Good News
Although the hazard is present, there have been --NO REPORTS OF
MERCURY VAPOR TOXICITY IN DENTAL OPERATORIES
Factors Affecting Mercury Leakage of Amalgam Capsules
1. Type of capsule ( single use or reusable capsule )
2. Mixing time (especially with high speed amalgamator)
3. Mixing speed
4. Temperature
5. Presence of piston
Jorgensen Method of Checking Leaky Amalgam Capsule
Winding adhesive plaster around Capsule --- trituration ---
inspection of the sticky surface of the plaster for mercury droplets
Methods of Detection of Mercury Vapor at Dental Operatory
1. Direct reading portable instrumentation (portable mercury
spectrometer)
2. Mercury absorption procedures: collecting systems ---
analytical lab.
3. Mercury dosimeter
Materials :
a. cadium sulphide
b. palladium chloride
c. gold film
The generally accepted Threshold Limit Value (TLV) for exposure to
mercury vapor for a 40-hour work weekly is 50 µg/m3
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5. Evaluation of Mercury Exposure Levels
In the working environment 50 µg/m3
In biological fluids
Urine : 150 µg/L
Saliva : 150 µg/100 mL
Blood : 0.1 mg/100 mL
Hair and Nails : 7 ppm
Amalgam waste management
Mercury-free direct metallic restorations
Amalgam replacement ( Ethical & Scientific issues)
Shouldn’t I ?
Many people want to replace their silver fillings because they
have heard that there is medical risk from the mercury in the
silver fillings.
There are no clinical studies to prove that there is any risk in
having a silver filling, so this should not be a reason for there
replacement.
Literature available upon request
Ethics
Unless new and compelling evidence is presented to the contrary,
dentists cannot ethically tell patients that dental amalgam is a
health hazard or that removal of amalgam restorations will
benefit their health.
When clinical research demonstrates that tooth-colored
restoratives are as economical and effective in the long-term as
dental amalgam, switch.
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6. Dental Mercury Hygiene Recommendations (ADA)
Store in an unbreakable tightly sealed containers
Use non-touch technique for amalgam handling
Work in well-ventilated spaces
Avoid carpeting dental operatories (decontamination is not
possible)
Avoid heating mercury or amalgam
Use water spray and suction when grinding amalgam
Do not use ultrasonic amalgam condensers
Perform yearly mercury determination on all personnel regularly
employed in dental offices
Have periodic mercury vapor level determination in operatories
Alert all dental personnel with the potential hazards of mercury
during handling dental amalgam
Clean up any spilled mercury immediately
Use tightly closed capsules during amalgamation
Perform all operation involving mercury over areas that have
impervious and lipped surfaces
Eliminate the use of mercury containing solutions
Use an amalgamator with completely closed arm
If possible, recap single use capsules after use and properly
dispose them
Remove professional clothing before leaving the work place
Conclusions
Continue to use amalgam unless esthetics is a concern
Use conservative preparations
Use resin sealants for non-carious fissures
Monitor research on bonded amalgams
Practice safe mercury hygiene
Stay informed!
Amalgam Restrictions
None in the United States
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7. Sweden, Denmark, and Germany have proposed restrictions on
amalgam use
The intent is to reduce the environmental release of Hg , it is not
due to amalgam restoration danger.
Environmental concerns may limit our usage, not the “mercury
poisoning” of our patients.
Again Judgment 4 U
“ Now R U Trusted In ………..!!!
Suggested Readings , Art & science of Operative Dentistry, Fourth
Edition 2002, Pages 158-168.
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