Mercury Toxicity

Mercury toxicity

The constant pronouncements about the toxic effects of mercury and the suggested links between dental amalgam and disease have confused and frightened the general public time and again.

While there is no scientific evidence whatsoever to support such claims, they continue to fuel the anti-amalgam fire.

HISTORY [Amalgam Wars]

In 1843, the American Society of Dental Surgeons condemned the use of all filling materials other than gold, thereby igniting the ‘first amalgam war’.

The second amalgam war was started by a German chemist, professor Alfred Stock in the mid 1920’s when Stock claimed to have evidence showing that mercury could be absorbed from dental amalgams and that this led to serious health problems. Stock reported that nearly all dentists had excess mercury in their urine.

The current controversy, sometimes termed the “Third Amalgam War” began primarily through the seminars of H.A. Huggins, a dentist from Colorado Springs.

He was convinced that mercury released from dental amalgam was responsible for a plethora of human diseases affecting the cardiovascular and nervous systems.

Mercury in the environment and food chain

Mercury is a naturally occurring element with 30,000 to 150,000 tons being released into the atmosphere by the degassing of the earth’s crust and the oceans.

Used in preparations such as diuretics, antibacterial agents, laxatives, skin antiseptics and other ointments.

Presently, workers in more than 60 industries are occupationally exposed to mercury.

These include factories producing chlorine, caustic soda, insecticides and fungicides as well as those involved in the manufacture of neon lights, paper and paint.

-Mercury enters the food chain by inadequate and improper disposal of wastes into oceans, lakes and streams where microorganisms methylate inorganic mercury to the more toxic methyl mercury.

-Methyl mercury is then rapidly taken up by plankton algae and is concentrated in fish via consumption by these organisms.

-From the aquatic environment, methyl mercury becomes incorporated in the terrestrial environment by species feeding on the aquatic organisms.

Sources of mercury in dental office.

These include

mercury spills

expression of excess mercury from amalgam

leakage from dispensers

leakage from amalgam capsules during trituration

mercury vaporization from contaminated instruments placed in sterilizers.

grinding of amalgam during removal of restorations

amalgam condensation with ultrasonic condensers

 contaminated furnishings of the office

contaminated amalgamators, cabinets, drains, drapes

waste containers

The mercury levels released as a result of various dental procedures

Exposure occurs through vapours in

Exterior & Oil based paints

Cosmetics

Toiletries.

METABOLISM

Different types of mercury metabolized by different methods.

ELEMENTAL MERCURY:Hg(O)

Solid state Hg(O) is not absorbed well in GIT.

Less than 0.1% is absorbed.

Remainder is excreted through urine and faeces.

Mercury has high vapour pressure

Vapours easily cross pulmonary alveolar membranes to circulatory system and eventually affect RBCs,CNS and kidneys.

In the system Hg(O)converts to HgCl2 and retained for years

Inhalation leads to:

1.     Chemical pneumonitis.

2.     Acute necrotizing bronchitis.

3.     Death from respiratory failure.

2.Inorganic mercury:Hg(+2)

About 10% of mercury salt is absorbed. Extremely caustic to GIT.

Half life of ingested mercuric salt is 40 days.

Toxic effects dependent on :

1.     Degree of solubility.

2.     Ability to combine with important enzymes

3.Organic mercury:

Methyl mercury has half life in blood of 30-40 days .

90% is excreted in feces through bile .

Methyl mercury is extremely neurotoxic and has following effects:

1.     Inhibits.

ü Micro tubular formation.

ü Protein synthesis in neurons.

2.Alters membrane activity.

3.Disturbs DNA synthesis.

ABSORPTION OF MERCURY

Effect of diet  on mercury metabolism:

Up to 85% of metabolized mercury comes from fish.

Once it enters the body it reacts with other nutrients from diet.

Methyl mercury binds to proteins:

1.     Albumin(from eggs)

2.     Sulfur containing proteins (from milk)

Nutritional factors which decrease mercury absorption are:

1.     Selenium plays a protective role against toxicity.

2.     Vitamin E and C (from nuts & orange juice)negate the formation of active O2  species in metabolism

3.     Amino acids (leucine &methonine) inhibit uptake of methyl mercury through amino acid transport system

MERCURY INHALATION

Mercury evaporates from the surface of the dental amalgam during setting

The total amount of mercury release for conventional(mean 870ng Hg for 24 hours) and high copper (mean 792ng Hg for 24hours)

Risk from mercury exposure :

Factors that determine risk from exposure include

1.     Dose.

2.     Duration .

3.     Type of contact.

Ø High risk population of mercury exposure:

o       Pregnant women or women who may become pregnant in next few years-methyl mercury can enter the mothers body and into the unborn infant and also breast feeding infants.

o       Young children(less than six years old)-their nervous system are still developing and have lower body weight.

o       Adults who consume larger amounts of contaminated fish on daily basis

MERCURY EXPOSURE IN DENTAL OFFICE

PICTURE FROM STURDEVANT

Dental amalgam contain about 46-56% of elemental mercury

After placement of filling there is persistent low level release of mercury vapor release into the body for many years

A single 0.4cm occlusal amalgam can release 15mcg of mercury vapor per day.

CATASTROPHE OF MERCURY

Ø MINAMATA BAY:

o       In 1950’ large amounts of  inorganic

    mercury were dumped into

    Minamata bay in Japan.

   It was dumped till 1986.

o       Inorganic mercury used as a catalyst in the ALDEHYDE process h was methylated inside the factory and then discharged into Minamata Bay

FETAL MINAMATA DISEASE

o       Mercury contaminated fish  were

     consumed by pregnant women,

     causing many children that

     were born from these  women

     with severe nerve damage, resulting in

1.severe mental retardation.

2.Absence of limbs

    

Ø IRAQ:

o       In studies of children born to mothers who consumed grain contaminated with organic mercury the effects showed the children walking at later age than non exposed children.

Ø FAROE ISLANDS:

o       Mercury exposure was caused by contaminated whale meat .

o       Children born to mothers with high body levels of mercury scored lower on brain function tests than mothers  with low body levels

CLINICAL FEATURES

ACUTE MERCURY POISINING:

Ø Abdominal pain.

Ø Vomiting.

Ø Diarrhea.

Ø Thirst.

Ø Pharyngitis.

Ø Gingivitis.

CHRONIC MERCURY EXPOSURE

Ø PINK DISEASE/SWIFT DISEASE IN INFANTS AND CHILDREN.

Ø Cold,clammy skin on hands, feet's, nose,ears and cheeks.

Ø Erythematous and pruritic rash is present.

Ø Severe sweating, Increased lacrimation, irritability, insomnia, photophobia, hypertension, weakness, tachycardia and GIT upset also present.

Ø Highly irritable children torn out patches of their hair.

ORAL SIGNS AND SYMPTOMS:

Ø Excessive salivation

Ø Bruxism

Ø Ulcerative gingivitis

Ø Premature loss of teeth

Ø Swollen gums

MAD HATTER’s disease

Ø In the story,ALICE THE WONDERLAND, the Mad hatter character was based on brain disease that commonly affected hat makers

Ø Early signs are insomnia, forgetfulness, loss of appetite and mild tremor.

Ø Diagnosed as psychiatric illness.

Conditions that suggest mercury toxicity

1.     Alzheimer’s disease.

2.     Multiple sclerosis.

3.     Cardiomyopathy.

4.     Angina.

DETOXIFICATION

1.Firstly remove the source of contamination.

2.DEAMALGAMATION:

Ø Determination of electro conductivity of filling.

Ø Protection of patient from acute mercury vapor’s by nasal mask to deliver fresh air.

Ø High speed drill with high intensity

Ø Cold water spray.

Ø Frequent cleansing of oral pockets by the dentist gloved fingers.

Some recommend I.V Ascorbic acid(vitamin c)during deamalgamation procedure to help chelate liberated mercury

Some recommend special laboratory testing be performed prior to selection of non mercury composite dental filling to be used.

Example:CLIFFORD MATERIALS REACTIVITY TESTS

3.NUTRIENT AGENTS:

I.GLUTATHIONE(GSH):

o       Vital in hepatic detoxification and elimination of mercury.

o       Serves as antioxidant.(systemic)

II.CYSTEINE:

o       All sulfur containing amino acids can chelate and remove mercury.

o       vitaminB12 and B6 is important in synthesis of sulfur containing amino acids and must be included in mercury detoxification regimen.

III.SELENIUM:

o       Essential trace element which is vital to protect against organic and inorganic mercury poisoning.

o       Activates GSH containing liver detoxification enzyme and also antioxidant enzyme glutathione peroxidase.

IV.VITAMIN E:

o       Works with selenium to neutralize mercury.

V.MICROACTIVATED ALGAE:

o       Such as chlorella and spirulina.

o       Detoxify organic and inorganic mercury.

VI.ALPHA-LIPOIC ACID(ALA):

Potent universal antioxidant.

It regenerates the endogenous antioxidant vit C,vit E and glutathione.

Repairs damaged tissues .

VII.ACTIVATED CHARCOAL:

Prescribed immediately before and after deamalgamation procedure to absorb and prevent enterohepatic recirculation of liberated mercury

4.PHARMACEUTICALS:

1.DIMERCAPROL:

Know as British Anti-Lewisite.(BAL).

First drug for heavy metal detoxification.

An antidote to Lewisite,an arsenical war gas used during II world war.

2.D-PENICILLAMINE

3.DMPS(2,3 DIMERCAPTO1-PROPANE SULFONIC ACID):

Water soluble derivative of dimercaprol.

Given by IV route and is less effective

4.DMSA(2,3DIMERCAPTOSUCCINIC ACID):

Important orally administered antidote.

Accelerates elimination of mercury from brain effectively removes mercury from blood,liver and kidneys.

Both DMSA and DMPS are sulfur containing compounds

DMSA is most effective of all.

Dosage :

10mg/kg in divided dose of 5-10 or                                                                                    more cycles of 3 days and 14 days

Another protocol is 500mg every other day for a minimum of 5 days

If patient is sensitive a suggested dose of 250 mg may be given every other day for 2-3 weeks followed by 500mg every other day for a total of 5 weeks.

5.EDTA(ETHYLENE DIAMINE TETRA ACETIC ACID):

Removes mercury from cell surfaces and from blood but not from within cells.

ANALYSIS OF MERCURY TOXICITY

1.HAIR ANALYSIS:

Only screening tool

Does not provide information about actual amount of mercury in the body

2.RBC ANALYSIS:

Gives information about tissue levels but misses mercury bound in brain,bone and fatty tissues

Blood levels reflect very recent exposure since mercury in blood has a short half-life, (destruction by erythrocytes) estimated to be about 3 days.

3.URINE ANALYSIS:

More accurate,practical and clinical measurement.

In this a dose of DMSA and Glycine is taken the evening before beginning the urine testà thereby extracting mercury from their hiding places deep in tissues which is then collected in urine thus giving more accurate measures

4.INTRAORAL VAPOR TESTING

It demonstrates that mercury is present in mouth from mercury filling

It’s a motivator ,but doesn’t show how much mercury is stored in body tissues.

The range of concentrations of mercury in urine and blood in general population, (not excessively or occupationally exposed to mercury) is 0 to 20 mg/L and 0 to 1.0mg / 100ml respectively.

100mg/m³    –          Clinical mercurism threshold      (LOAEL)

            50mg/m³      –          Nephrotoxicity threshold                         (LOAEL)

            25mg/m³      –         WHO industrial threshold                        (NOAEL)

            5mg/m³         –         General public threshold                         (NOAEL)

            1mg/m³          –         Children, pregnant, sick threshold (NOAEL)

The Threshold Limit Value (TLV) is the concentration of mercury vapor to which nearly all workers may be repeatedly exposed without adverse effects. The TLV recommended by OSHA is 50mg/m³, based on a time-weighted average during an 8 hours work shift over a 40 hours workweek.

LOAEL – Lowest Observed Adverse Effect Level – is the lowest level at which an adverse effect has been observed.

NOAEL – No Observed Adverse Effect Level – is the level at which adverseeffects have never been observed.

MERCURY HYGIENE MEASURES

Should be stored in closets or cabinets to minimize local concentration inrest of office

Local spill should not be collected with vacuum aspirants.spilled mercury can be made harmless by dusting with sulfur or by spraying sodium thiosulphate.

Mercury droplets are difficult to remove from artificial floor coverings so floor coverings should be avoided.

Mercury vapors should be monitored periodically.

Current limit for mercury vapor established by OSHA is 50micro g/m3 in an 8 hour shift over a 40 hour work week

Scrap dental amalgam from condensation procedures should be collected  and stored under water, glycerin or spent X-ray fixer in a tightly capped jar.

Provide proper ventilation in work place by having fresh air exchanger and proper replacements of filters which may act as trap of mercury

Precapsulated alloys should be used to eliminate the possibility of bulk mercury spill.

Amalgamator should be covered.

Skin contact with mercury or freshly prepared amalgam should be avoided.

Change mask after removing amalgam restorations.

Mercury contaminated items should be deposited in sealed bags.

Office personnel should be periodically monitored.

MONITORING MERCURY LEVELS

Can be determined by using a mercury detection meter such as mercury sniffer.

such meters are costly.

Paper discs impregnated with palladium chloride can be used.

A badge system may be used in which mercury is adsorbed on gold foil.

Mercury in vapor and dust form may be determined by passing the known volume of air through an absorbing system and then quantifying the absorbed mercury.

CONCLUSION

Like a two edged sword mercury has both indications and contraindications in both medical and dental fields.

So the clinician should have knowledge about pros and cons of mercury and the clinician should use the mercury with caution.