Mercury in Restorative Dentistry

transcript

Presented by : Dr Aswin. S

Contents Introduction History Manufacturing of mercury Properties :- General Physical Properties. Chemical Properties. Compounds Inorganic Organic Elemental (Vapour) Occurrence Applications:- Medicine and Dental Laboratory uses Other uses

Mercury cycle Mercury in dental amalgam Amalgam reactions Amalgam wars PHYSIOLOGICAL Hg CYCLE Toxicity and safety Mercury toxicity levels Effects of mercury toxicity on body - Allergy - Acute poisoning -Chronic poisoning -Oral cavity problems - Acrodynia

-Minimata disease -Hunter-Russell syndrome - Erethism

Treatment Laboratory test Methods to detect mercury vapor release. Mercury exposure in dental practice Mercury Management. ADA Dental Mercury hygiene recommendation. Amalgam waste management. Conclusion. References. Previous year questions.

INTRODUCTION Mercury is a heavy, silvery-white

liquid metal. Also known as quick silver. Mercury is the only common metal

which is liquid at ordinary temperatures.

Poor conductor of heat if compared with other metals.

A fair conductor of electricity. It alloys easily with many metals,

such as gold, silver, and tin. These alloys are called amalgams.

‘Mercury’ was the name of the Roman’s messengers of the gods who were believed to be really fast moving.

The name comes from Greek name, hydrargyrum, which means "liquid silver”

to reflect its shiny surface Mercury was named ‘Mercury’ because

it, as a liquid, flows quickly. It’s also called quicksilver because in

addition to its quick flowing property, it has a silvery tinge.

History Mercury was a well-known metal in the ancient

time in China, India, and Egypt.

1500 BC : Found in Egyptian tombs. It was used to prolong life, heal fractures, and maintain generally good health.

500 BC : Ancient Greeks-ointments. Ancient Egyptians and Romans- cosmetics Maya civilization-began making amalgams

247 BC -221 BC: China’s first emperor, Qin Shi Huang Di - who unified China was killed by mercury pills intended to give him eternal life.

1 AD :The Roman scholar Pliny described mercury poisoning as a disease of slaves because mines contaminated by mercury vapour were considered too unhealthy for Roman citizens.

659AD Amalgam -- First used by Chinese. There is a mention of silver mercury paste by Sukung

in the Chinese medic

1525 : Paracelsus, a Roman doctor developed treatments using mercury and potassium salts.

1528 : Germany-used for dental purposes.

1800 : in France alloy of bismuth, lead, tin and mercury plasticized at 100ºC poured directly into cavity.

1816:Aguste Taveau of Paris developed was probably the first dental amalgam by using filings from silver coins mixed with mercury.

1833:Crawcour brothers brought dental amalgam to the US.

1844 : 50% of restorations were silver amalgam.

1840 - 1850 : Bitter controversy about the merits and deficiencies of mercury amalgam.(FIRST AMALGAM WAR-1843)

1856 : Dispute ended and formation of ADA in 1859.

1895 : G.V.Black standardized both cavity preparation and the amalgam manufacture.

1900 : Introduction of copper amalgams

1926 : Second amalgam war.

1956 : Minamata disease officially acknowledged .

1976 :FDA pronounced acceptance of amalgam filling approved dental amalgam under safe category

1980 : Third Amalgam War began.

1990:First controlled research on dental amalgam effects published.

1991: National institute of health technology assessment panel on dental materials issued a statement that amalgam is safe.

1997 Sweden banned dental mercury amalgam.

In 2008, Norway and Denmark banned dental mercury amalgam

2013 The final mercury treaty session took place in Geneva. Treaty requested countries to phase down the use of dental amalgam.

Dec. 8, 2016 The European Union (E.U.), with 28 member nations declared , will prohibit the use of dental amalgam in children under 16 and in pregnant and breastfeeding women effective from July 1, 2018.

Manufacture of mercuryMining Cinnabar is dislodged from the surrounding rocks by drilling

and blasting with explosives or by the use of power equipment.Roasting The ore is first crushed in one or more cone crushers. The crushed ore is then ground even smaller by a series of

mills. The finely powdered ore is fed into a furnace or kiln to be

heated. The heated cinnabar (HgS) reacts with the oxygen (02) in the

air to produce sulfur dioxide (SO 2 ), allowing the mercury to rise as a vapor. This process is called roasting.

Condensingo The mercury vapor rises up and out of the furnace or

kiln along with the sulfur dioxide, water vapor, and other products of combustion.

o The hot furnace exhaust passes through a water-cooled condenser.

o As the exhaust cools, the mercury, which has a boiling point of 357° C, is the first to condense into a liquid, leaving the other gases and vapors to be vented.

o The liquid mercury is collected. Because mercury has a very high specific gravity, any impurities tend to rise to the surface and form a dark film or scum.

o These impurities are removed by filtration

Refiningo The most common refining method is

triple distillation, in which the temperature of the liquid mercury is carefully raised until the impurities either evaporate or the mercury itself evaporates, leaving the impurities behind.

o This distillation process is performed three times, with the purity increasing each time.

Mercury in the environment

Mercury is a compound that can be found naturally in the environment as metal form, mercury salts or as organic mercury compounds

Found mainly in cinnabar ore (HgS) in Spain, Russia, Italy, China and Slovenia.

Also present as an impurity in many other minerals, in particular the non-ferrous metals, and in fossil fuels, coal. Cinnabar ore

Lyman SN, Jaffe DA. Formation and fate of oxidized mercury in the upper troposphere and lower stratosphere. Nature Geoscience. 2012 Feb 1;5(2):114-7.

Mercury occurs uncombined in nature to a limited extent.

Mining and the burning of coal, has increased the mobilization of mercury into the environment

Raising the amounts in the atmosphere, soils, fresh waters, and oceans.

General properties:

Appearance Silvery

Atomic number 80

Standard atomic weight 200.592 g/mol

Element category Transition metal

Physical properties

Phase LiquidMelting point 38.8290 ̊ CBoiling point 356.73 ̊ CDensity 13.534g/cm3

Critical point 172.00 MPaHeat of fusion 2.29KJ/mol

Chemical properties

Electronegativity according to Pauling

Vanderwaals radius 0.157 nm

Isotopes 2

Forms of Mercury I. Elemental mercury. Most common form It is metallic , silvery liquid Easily vaporize in room

temperature into an odorless , colorless vapor that can easily inhaled.

Schaefer JK. Biogeochemistry: Better living through mercury. Nature Geoscience. 2016 Jan 18.

Risks Easily crosses blood brain barrier and

can enter breast milk Potent neurotoxin Neurological effects - tremors , mood

swings, irritability, excessive shyness Very high exposure can cause kidney

effects, respiratory failure and death

II. Inorganic mercury White in color except cinnabar (Red). Enters body through mouth and skin from

disinfectant and fungicide. Usually used in school science lab. Least toxic of three forms Can damage GI tract, kidney and nervous

system. it form two series of compounds Mercuric: soluble and more toxic Mercurous: less soluble, thus, less active

2. Mercuric chloride: (corrosive sublimate). Occurs as odorless, white crystalline powder, nauseous, metallic taste and soluble in water, alcohol, ether, glycerin.Used in medicines and taxidermy.

2.Mercurous chloride: (ras kapoor, calomel). Heavy amorphous white tasteless powder, insoluble in water, alcohol and ether. On exposure to light turns to Mercuric chloride. Used in laxatives.

Mercuric sulphide: (ras sindoor, cinnabar).

Used as a red pigment, it is known as vermilion.

Vapour is poisonous.

III. Organic mercury Methyl mercury most commonly found in

environment and most toxic form of Hg. Converted from its inorganic form by biological

bacterial process. Bio accumulates in environment most commonly

found in fish. Ingestion of fish is most common route of human

mercury exposure

Risk Birth defects Neurological problems Impairment of vision, speech, walking Extreme exposure leads to death

Applications of mercuryMedicine:Mercury and its

compounds have been used in medicine.

Less common today due to toxic effects.

Traditional medicine-diuretic, topical disinfectant and laxative.

Once used to treat syphilis. Antibacterial agents

Dentistry: Amalgam alloy with mercury-dental fillings.

Gasper JD, Aiken GR, Ryan JN. A critical review of three methods used for the measurement of mercury (Hg 2+)-dissolved organic matter stability constants. Applied Geochemistry. 2007 Aug 31;22(8):1583-97.

Laboratory uses: Medical thermometers Sphygmomanometer ,

thermometers Liquid mirror telescope

Other uses: mercury vapor

lamps Fluorescent lamps

and neon signs barometers,

batteries electrical switches Cosmetics: used as

thiomersal for manufacture of mascara.

Natural and human activities release elemental mercury vapor (Hg0) into the atmosphere.

Once in the atmosphere, the mercury vapor can circulate for up to a year.

Mercury vapor can then undergo a photochemical oxidation to become inorganic mercury that can combine with water vapors and travel back to the Earth’s surface as rain.

In water, inorganic mercury can be converted into insoluble mercury sulfide which settles out of the water, or it can be converted by bacteria that process sulfate into methylmercury.

Now the methylmercury-processing bacteria may be consumed by the next higher organism up the food chain.

This pattern continues as small fish/organisms get eaten by progressively bigger and bigger fish until the fish are finally eaten by humans.

Dental amalgam Dental amalgam has been used for

more than 150 years. Dental amalgam is a mixture of metals,

consisting of liquid (elemental) mercury and a powdered alloy composed of silver, tin, and copper.

ADA specification for mercury

The mercury shall have a bright mirror like surface free from any film or scum.

Mercury has no surface contamination and less than 0.02% of nonvolatile residue.

Should be triple distilled and pure.

The most common refining method The temperature of the liquid

mercury is carefully raised until the impurities either evaporate or the mercury itself evaporates, leaving the impurities behind.

This distillation process is performed three times, with the purity increasing each time.

Triple distillation

PROPOTIONING THE ALLOY AND MERCURY

The amount of mercury in dental amalgam may be specified as alloy – mercury ratio.

Ratios varies for different technique and handling characteristics used by dentist.

The most obvious method to reduce mercury content is minimal mercury technique or Eames technique mercury:alloy=1:1.

Alloy- mercury ratio

Phillip’s science of dental materials south east edition 2015

Use preweighted pellets of alloy and dispense mercury from volumetric dispenser.

If amalgam alloy and mercury dispenser are from different manufacturers pellet must be weighed.

The amount of mercury needed can be calculated from pellet weight.

Measuring alloy and mercury

Correct weight of mercury is calculated by

if X- weight of mercury Y – weight of alloyThen weight of mercury = X gram Y

Removing excess mercury When mortar and pestle were used for mixing

excess mercury is added to achieve smooth and plastic amalgam.

Removal of excess mercury was done by I) Initially removed with the help of the cloth by squeezing through it. II ) Increasing dryness technique, during condensation of each increment a mercury rich soft layer comes to the surface.o Mulling is done to redistribute mercury within in

mixed , squeezed mass.

They contain pre weighted mercury and alloy in separate compartments.

Mercury is released by twisting cap in one type of capsule

In other type motion of the amalgamator arms bring mercury and alloy together.

Disadvantages are dentist have no opportunity to make minor adjustment in the mix

Amalgam capsule

Trituration

The objective of trituration is to provide proper amalgamation of the mercury and the alloy.

The alloy particles are coated oxide layer that hinder diffusion of mercury into alloy.

This layer is removed by abrasion when alloy particles and mercury are triturated .

Types- hand mixing mechanical mixing

Effect of mercury content

dry granular mixrough & pitted surfacecorrosion

high mercury contentmore γ2

low mercury contentmore

unreacted AgSn particlesimparts

strength to restoration

sufficient mercury should be mixed with the alloy to wet each particle of the

More mercury , more will be the expansion, as more crystals will grow.

Low mercury: alloy ratio favors contraction During trituration, if more energy is used for

manipulation, the smaller the particles will become , mercury will be pushed between the particles, discouraging expansion.

More the condensation pressure used during condensation, closer the particles are brought together; more mercury is expressed out of mix inducing more contraction.

Factors that affect the dimensional change of amalgam

Creep Creep occurs when a solid material

slowly deforms plastically under influence of stress.High mercury content increases creep.Mercury content beyond 46% produces sudden increase in creep

Amalgamation Reaction – Low Copper Alloys

A- Dissolution of silver and tin into mercury

B- precipitation of 1crystals in mercury

Ag3Sn + Hg Þ Ag3Sn + Ag2Hg3 + Sn8Hg 1 2

C- consumption of the mercury by growth of 1 and 2 grains

D - The final set amalgam

γ1 forms first and then γ2 Alloy is mixed with mercury in the ratio

of 1:1 Mercury is insufficient to completely

consume the alloy particles γ1 - Dominant phase – 54-56%Unreacted γ - 27- 35%γ2 - 11-13%

CRAIG’s Restorative Dental Materials;13th edition2012

Gamma () = Ag3Sn unreacted alloy strongest phase and

corrodes the least forms 30% of volume

of set amalgam

Gamma 1 (1) = Ag2Hg3 matrix for unreacted alloy

and 2nd strongest phase 60% of volume

γ2 phase is extremely weak & soft, deforming readily & the strength of amalgam is limited by its presence

Contributes to static creep of amalgam

Admixed High-Copper Alloys Initial reaction

Ag3Sn + Ag-Cu + Hg ÞAg3Sn + Ag2Hg3 + Sn8Hg + Ag-Cu

Ag-Sn Alloy

Mercury

AgAgAg

Ag-Cu Alloy

AgHgHg

Final reaction Ag-Cu Alloy

Ag-Sn Alloy

2 Sn8Hg + Ag-Cu Þ Cu6Sn5 + Ag2Hg3 + Ag-Cu

1Phillip’s science of dental materials south east edition 2015

Single Composition High-Copper Alloys

Ag-Sn Alloy

Ag-Sn AlloyAg-Sn Alloy

Ag3Sn + Cu3Sn + Hg Ag2Hg3 + Cu6Sn5 + Ag3Sn +Cu3Sn 1

MERCURY FREE AMALGAM

Gallium based alloy It is metal With similar atomic structure and

characteristics to mercury. Hence , by 1928 Puttkammer suggested Gallium as a

substitute for mercury DISADVATAGES . Handling characteristics of alloy not favorable . High level of corrosion marginal disintegration . Dimensional change of 21.5% . Poor biocompatibility . costly

Sturdevant's Art and Science of Operative Dentistry South east edition 2013

The first amalgam war In 1845, American Society of Dental

Surgeons condemned the use of all filling material other than gold as toxic, thereby igniting "first amalgam war'. The society went further and requested members to sign a pledge refusing to use amalgam.

AMALGAM WARS

The amalgam controversy-an evidence based analysis ; JADA,Vol.132,march 2001

What ended the amalgam war?? Professional and consumer demand. In 1859, the leaders of the profession

regrouped to form the American Dental Association.

Second amalgam war….

In mid 1920's a German dentist, Professor A. Stock started the "second amalgam war". He claimed to have evidence showing that mercury could be absorbed from dental amalgam, which leads to serious health problems. He also expressed concerns over health of dentists, stating that nearly all dentists had excess mercury in their urine.

Remarkably, the Food and Drug Administration (FDA) has separately approved the mercury and the alloy powder for dental use; but the amalgam mixture has never been approved as a dental device

Unfortunately now came the second world war over Europe &" the second amalgam war" fell in forgetfulness

3rd amalgam war in 1980s Third Amalgam War' began in 1980

primarily through the seminars and writings of Dr.Huggins.

He was convinced that mercury released from dental amalgam was responsible for human diseases affecting the cardiovascular system and nervous system

Also stated that patients claimed recoveries from multiple sclerosis, Alzheimer’s disease and other diseases as a result of removing their dental amalgam fillings.

3rd amalgam war in 1980s

But the ADA remained adamant that mercury in patients' mouths is safe, and in 1986 it changed its code of ethics, making it unethical for a dentist to recommend the removal of amalgam because of mercury

But problem flared in 1990’s by the telecast of television program ‘60 minutes’ in CBC television

PHYSIOLOGICAL Hg CYCLE

ElementalHg

InorganicHg

OrganicHg

GITRACT

Allothersites

Hair,Nails

EXFOLIATION ofSkin, Hair, Nails

Average Half-Life in Human Body = 55 Days

ABSORPTIONROUTE

TRANSPORTION andLOCALIZATION

EXCRETIONof Hg

HgFORM

Sources of Mercury Exposure Ingestion of contaminated fish Occupational exposure Coal burning and mining Outgassing of mercury from dental

amalgam

Hg levels

OSHARECOMMENDED TLV=0.05mg/m³

MOST Dental office mercury level lie below 0.05mg/m³

TOXIC EFFECTS OF MERCURY DEPEND UPON

- Amount of exposure - Length of exposure - Length of mercury accumulation in body - Amount of accumulated mercury - Overall health of the patient ( for detoxification)

Effects of Mercury toxicity on the body

ALLERGY Allergy responses represent an antigen-antibody

reaction marked by itching, rashes, sneezing, or other symptoms

Contact dermatitis or Comb's type IV hypersensitivity reaction represent the most likely physiologic side effect to dental amalgam

When such a reaction has been documented by dermatologist or allergist, an alternative material (e.g. Composite or ceramic) must be used.

Phillip’s science of dental materials south east edition 2015Bernhoft RA. Mercury toxicity and treatment: a review of the literature. Journal of environmental and public health. 2011 Dec 22;2012.

Immediate Hyper sensitivity reaction associated with the mercury component of amalgam restoration

Release of mercury induced an acute reaction which resulted in erythematous lesions, severe burning and itchy sensation and difficulty in breathing Skin patch test results indicated a very strong positive reaction to mercury Amalgam restorations were replaced with composite filling material

Bernhoft RA. Mercury toxicity and treatment: a review of the literature. Journal of environmental and public health. 2011 Dec 22;2012.

TOXIC EFFECT ON MERCURYFORM OF MERCURY

ELEMENTAL INORGANIC METHYL MERCURY

ROUTE OF EXPOSURE

INHALTION ORAL ORAL –FISHCONSUMPTION

TARGET ORGAN

CNS , KidneyPeripheral nervous system

KIDNEY, PNS CNS

LOCAL CLINICAL SIGN

Lung ;bronchial irritation

GI-irritationSkin – irritation ulceration

SYSTEMIC EFFECTS

Kidney-proteinuriaCNS –mood changePNS - Tremors

Kidney – proteinuria,Tubular necrosis PNS -TremorsNumbness

Developmental defects in fetus and newborn.CNS - In adult Tremors Paraesthesia

Inhalation of mercury vapors causes

Chemical pneumonia Pulmonary oedema Gingivostomatitis Increased salivation

CNS symptoms like Ataxia Restriction of field of vision Delerium Polyneuropathy.

Acute poisoning

The signs and symptoms start immediately after swallowing the mercury:

Acrid metallic taste in mouth. Feeling of constriction or choking of throat. Hoarseness of voice. Difficulty in breathing Hot burning pain in mouth, stomach and abdomen. Stools are blood stained , urine is suppressed and

scanty, contain blood and albumin is accompanied by necrosis of renal tubules and damage to the glomeruli.

Ingestion of Mercury

Houston MC. Role of mercury toxicity in hypertension, cardiovascular disease, and stroke. The Journal of Clinical Hypertension. 2011 Aug 1;13(8):621-7.

Pulse is quick small and irregular Thrombocytopenia and bone marrow depression.

Workers may get poisoned due to vapors or dust.

When small doses are taken for prolonged time or used as ointment for long period.

The signs and symptoms of chronic mercury start at a blood level 100 mg/ml.

Patient is symptomatic at daily urinary excretion more than 300 mg/ml

Chronic Mercury Poisoning/ Hydrargyrism

Excessive salivation with swollen and painful salivary glands.

Foul smelling breathing, inflamed and ulcerated gums with brownish blue line and loosening of teeth.

Mercura lentis: A brownish reflex from the anterior lens capsule of both the eyes is seen when observed in slit lamp in person exposed to mercury vapors for some years. It is bilateral and has no effect on the visual acuity.

Signs and symptoms

ORAL CAVITY PROBLEMS

Inflammation of the mouth

Loss of bone around teeth

Ulcerated gums and other areas in the mouth

Darkening of gums Taste of metal Bleeding gums

Acrodynia (Pink disease) There is generalized rashes

over the body. Results from chronic exposure

to mercury in any forms. Erythematous, eczematous

(watery and weeping) popular type of skin lesion

Mostly in the hands and feet accompanied with thickening of skin.

Tunnessen WW, McMahon KJ, Baser M. Acrodynia: exposure to mercury from fluorescent light bulbs. Pediatrics. 1987 May 1;79(5):786-9.

Desquamating rash Hair loss Tachycardia, hypertension Photophobia Irritability, Constipation/Diarrhea Anorexia Insomnia Poor muscle tone

Hunter-Russell syndrome The term Hunter-Russell

syndrome derives from a study of mercury poisoning among workers in a seed packing factory in England in the late 1930s who breathed methyl mercury that was being used as a seed disinfectant and preservative.

Syndrome is characterized by paresthesia, visual field constriction, ataxia, impaired hearing, and speech impairment.

Tokuomi H, Kinoshita Y, Teramoto J, Imanishi K. Hunter-Russell syndrome. Nihon rinsho.Japanese journal of clinical medicine. 2004 Dec;35:518-9.

In 19th century, inorganic mercury in the form of mercuric nitrate was commonly used in the production of hats.

It caused a slow release of volatile free mercury. Erethism commonly characterized by behavioral

changes such as irritability, low self-confidence, depression, apathy, shyness and timidity.

In some extreme cases delirium personality changes and memory loss occur.

Erethism

(Mad hatter disease, or mad hatter syndrome)

Waldron HA (2003). "Did the Mad Hatter have mercury poisoning?" British Medical Journal (Clinical Research Edition). 287 (6409): doi:10.1136/bmj .287.6409.1961. PMC 1550196. PMID 6418283.FDA. "Dental Amalgam" Retrieved 3 April 2014

Minamata disease A local chemical plant (Chisso Corporation) disposed

methyl mercury waste into the nearby bay, in Japan in 1952 contaminating the shellfish and causing toxic levels of mercury of the fish eaten by the local population.

By the time the source was identified, 52 individuals had died by mercury poisoning.

Since this time, mercury poisoning of this kind is known as Minamata disease.

Harada M. Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Critical reviews in toxicology. 1999 Jan 1;25(1):1-24.

Symptoms were:- 1.Ataxic gait 2.Convulsions 3.Numbness in mouth & limbs 4.Constriction in the visual field 5.Difficulty in speaking.

Chelation therapy is the administration of chelating agents which bind mercury ions and facilitate their excretion through urine and feces.

A chelating agent could be given orally, I.M, I.V .

Only Dimercaptosuccinic acid (DMSA) is FDA approved for treating children with Hg toxicity

2,3-dimercapto-1-propanesulfonic Acid(DMPS) D-pencillamine(DPCN) Dimercaprol (BAL) DMSA is the most frequently used for severe

methylmercury poisoning.

Treatment

Hall JL. Cellular mechanisms for heavy metal detoxification and tolerance. Journal of experimental botany. 2009 Jan 1;53(366):1-1.

α-Lipoic acid (ALA) If Kidneys show signs of damage

peritoneal dialysis or hemodialysis may be necessary.

Treatment of shock and collapse are also required.

5-10% sulphoxylate and 5% sodium bi carbonate is used for stomach wash. This is beneficial if given in the first half an hour

If colitis has developed, high colonic lavage given with 1: 1000 solution of sulphoxylate.

B.A.L is to be given in the dose of :

3-5mg/kg 4 hourly for 2 days. 2.5 mg/kg 6 hourly for1 day. 2.5 mg/kg twice daily according to the

severity.

For diuresis5-10% glucose is used in normal saline.Hall JL. Cellular mechanisms for heavy metal detoxification and tolerance. Journal of experimental botany. 2009 Jan 1;53(366):1-1.

Symptomatic patients who have experienced acute high-dose elemental mercury inhalation exposure should receive supportive care and be monitored for development of acute pneumonitis and pulmonary edema in a hospital setting.

Laboratory Tests Urine levels of mercury

provide the most appropriate assessment of elemental mercury exposure and are useful for the assessment of acute and chronic exposures.

A urinary mercury concentration of less than 4 micrograms per liter (μg/L)

would be considered within the background range.

Urine test

Wilhelm M, Müller F, Idel H. Biological monitoring of mercury vapour exposure by scalp hair analysis in comparison to blood and urine. Toxicology letters. 1996 Nov 30;88(1):221-6

Blood is primarily tested to detect the presence of methyl mercury.

Amount present will decrease by half about every 3 days as the mercury moves into organs such as the brain and kidneys.

Therefore, blood testing must be done within days of suspected exposure

Blood level greater than 10 mcg/L indicates an unusual level of exposure for someone who does not regularly work with mercury.

Blood test

Analyzing Hair Hair analysis primarily

measures organic (methyl) mercury exposure only and is not useful for assessing recent exposures.

In cases of occupational exposure to mercury vapour, hair is an useful tool for monitoring external exposure.

Wilhelm M, Müller F, Idel H. Biological monitoring of mercury vapour exposure by scalp hair analysis in comparison to blood and urine. Toxicology letters. 1996 Nov 30;88(1):221-6.

A study was done by Michael Wilhelm and Frank Miillerb, on ‘Biological monitoring of mercury vapour exposure by scalp hair analysis in comparison to blood and urine’. It concluded that hair may be used as an indicator of internal uptake of mercury provided that it was not externally exposed to mercury vapour.

Wilhelm M, Müller F, Idel H. Biological monitoring of mercury vapour exposure by scalp hair analysis in comparison to blood and urine. Toxicology letters. 1996 Nov 30;88(1):221-6.

Methods of detect mercury vapour release

Photoionization detector PID is a type of gas detector. PIDs produce instantaneous

readings, operate continuously, and are commonly used as detectors for gas chromatography.

Used to monitor. Industrial hygiene and safety.

Environmental contamination Hazardous materials handling Indoor air quality Haag, W.R. and Wrenn, C.: The PID Handbook - Theory and Applications of Direct-Reading Photoionization Detectors (PIDs), 2nd. Ed., San Jose, CA: RAE Systems Inc. (2006)

Gold film mercury vapour detectives First reliable forms of detectors

due to gold’s affinity for elemental mercury.

When a mercury rich air sample passes over a thin gold film, the mercury deposits on the gold and changes the electrical resistance of the foil.

This change in resistance is directly proportional to the mass of mercury vapor taken from a known volume of air, which can be calculated in mg/m3.

Urba A, Kvietkus K, Sakalys J, Xiao Z, Lindqvist O. A new sensitive and portable mercury vapor analyzer GARDIS-1A. InMercury as a Global Pollutant 2008 (pp. 1305-1309). Springer Netherlands.

Photoacoustic spectroscopy

Photoacoustic spectroscopy is a technique in which a substance absorbs a pulsed beam of light and transforms the absorbed energy into thermal energy of the surrounding gas.

The absorbed energy from the light causes local heating and through thermal expansion a pressure wave or sound, be sensed by a microphone.

Rosencwaig A, Gersho A. Theory of the photoacoustic effect with solids. Journal of Applied Physics. 1998 Jan;47(1):64-9.

Cold Vapor Mercury Analysis Involves the conversion of Hg salts to

Hg vapor using an strong acidic reducing agent such as Sn/HCl

Atomic absorption or Atomic fluorescence are common detectors for this analysis.

Now PID is also available for this analysis

KOPYsc E, PYRZYnska K, Garbos S, BULSKA E. Determination of mercury by cold-vapor atomic absorption spectrometry with preconcentration on a gold-trap. Analytical sciences. 2000;16(12):1309-12.

Dosimeter Dosimeter - Badge system

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

Worn by the personnel in dental office.

MERCURY EXPOSURE IN DENTAL PRACTICE.

Exposure of mercury may be either in the form of vapour or particulate amalgam dust .

Mercury vapors -> passes into intra oral air and then enters lungs.

Mercury ion (Hg2+) -> passes into saliva to enter GIT.

Amounts of Mercury released

Trituration : 1-2 μg Placement of restorations : 6-8 μg Dry Polishing : 44μg Wet Polishing : 2.4 μg

Removal of restorations using water spray and high volume suction : 1.5 - 2μg

Additional evacuation for 1 minute to remove amalgam dust : 1.5 – 2 μg

MERCURY MANAGEMENT

Spills of triturated materials are collected with vacuum aspirator.

Vapor releases must be cleared by airflow system of room.

During intra oral placement and condensation procedure rubber dam can be used to isolate patient and high vacuum evacuation is used.

Storages location should be near a vent that exhaust air out of the building.

Before use : Store in a plastic container with threaded cover

Scrap amalgam, from condensation is stored under water , glycine or spent x ray fixer and tightly capped jar.

ADA RECOMMENDATIONS FOR DENTAL MERCURY HYGEINE Train all personnel regarding mercury handling

and hazards. Make them aware of the potential sources of

mercury vapor in the operatory. Work in well ventilated spaces with an exhaust.

Replace air conditioning filters periodically. Monitor the dental operatory atmosphere for

mercury vapor.

Design work area properly. Floor covering should be nonabsorbent, seamless and easy to clean.

Use precapsulated alloys. Use amalgamator with completely enclosed arm. Avoid skin contact with mercury or freshly

prepared amalgam. Re-cap single use capsules after use if possible.

Use high volume evacuation while finishing or removing amalgam.

Salvage and store all scrap amalgam.

Dispose amalgam scrap and mercury contaminated items as per applicable regulations.

Clean up spilled mercury using trap bottles, tape or freshly mixed amalgam. Do not use household vacuum cleaner.

Remove professional clothing before leaving the workplace.Sturdevant's Art and Science of Operative Dentistry South east edition 2013

MANAGEMENT OF MERCURY SPILLSIn case of an accidental mercury spill (regardless of size), Never use a vacuum cleaner to clean up the mercury. Never use household cleaning products to clean up the

spill, particularly those containing ammonia or chlorine. Never allow mercury to go down the drain. Never use a broom or a paintbrush to clean up the

mercury. Never allow people whose shoes may be contaminated

with mercury to walk around.

Dental mercury hygiene recommendation. J am Dent Assoc 2003;134:1498.

MERCURY SPILLAGE KIT Spill kits are essential for the

management of mercury spills and breakages.

Procedure Put on the Personal Protective Equipment which is provided in the kit Using the scoop collect the amalgam or mercury waste If it is mercury droplets use the syringe to pick up as many

globules. Then place the full syringe in the waste container (provided in the kit)

Open the container which contains calcium hydroxide and sulphur .

Tip out onto the spillage area, close the center of the spillage Using the scoop mix the powders with the spilt amalgam or

mercury (which you could not pick up) The powder may start to go grey as the mercury is absorbed.

Baughman TA. Elemental mercury spills. Environmental health perspectives. 2006 Feb 1:147-52.

Brush the contaminated powder into the scoop and place in the waste container.

Close the lid on the waste container or sealable bag.

Dispose of the Personal Protective Equipment in the waste container .

Label the waste container or bag with ‘hazardous waste sign’

Contact the licensed waste carrier company you use to remove the hazardous waste.

Cleanup of large mercury spills requires experienced environmental personnel.

Mercury disposal

Alternatives to Dental Amalgam

Composite Glass ionomer cement Ivoclar cention

FDA. "Dental Amalgam" Retrieved 3 April 2014

Conclusion The risk of mercury exposure to dental personnel

cannot be ignored, but close adherence to simple hygiene procedures helps ensure a safe working environment.

Dentist must observe strict amalgam hygiene procedures so that the health of dental workers is not put at risk.

It is also necessary to safety dispose mercury. Prevention from reaching the sewage system to

avoid environmental contamination is necessary.

Reference história do amálgama em Odontologia A. History of

Amalgam in Dentistry. Rev. Clín. Pesq. Odontol. 2007 Jan;3(1):65-71.

Lyman SN, Jaffe DA. Formation and fate of oxidized mercury in the upper troposphere and lower stratosphere. Nature Geoscience. 2012 Feb 1;5(2):114-7

Gasper JD, Aiken GR, Ryan JN. A critical review of three methods used for the

measurement of mercury (Hg 2+)-dissolved organic matter stability constants.

Applied Geochemistry. 2007 Aug 31;22(8):1583-97

CRAIG’s Restorative Dental Materials;13th edition2012 The amalgam controversy-an evidence based

analysis ; JADA,Vol.132,march 2001 Bernhoft RA. Mercury toxicity and treatment: a

review of the literature. Journal of environmental and public health. 2011 Dec

22;2012. Houston MC. Role of mercury toxicity in hypertension,

cardiovascular disease, and stroke. The Journal of Clinical

Hypertension. 2011 Aug 1;13(8):621-7.

Tunnessen WW, McMahon KJ, Baser M. Acrodynia: exposure to mercury from fluorescent light bulbs. Pediatrics. 1987 May 1;79(5):786-9

Tokuomi H, Kinoshita Y, Teramoto J, Imanishi K. Hunter-Russell syndrome. Nihon rinsho.Japanese journal of clinical medicine. 2004 Dec;35:518-9

Waldron HA (2003). "Did the Mad Hatter have mercury poisoning?" British Medical Journal (Clinical Research Edition). 287 (6409): doi:10.1136/bmj .287.6409.1961. PMC 1550196. PMID 6418283.

FDA. "Dental Amalgam" Retrieved 3 April 2014 Harada M. Minamata disease: methylmercury poisoning

in Japan caused by environmental pollution. Critical reviews in toxicology. 1999 Jan 1;25(1):1-24

Hall JL. Cellular mechanisms for heavy metal detoxification and tolerance.Journal of experimental botany. 2009 Jan 1;53(366):1-1

Haag, W.R. and Wrenn, C.: The PID Handbook - Theory and Applications of Direct-Reading Photoionization Detectors (PIDs), 2nd. Ed., San Jose, CA: RAE Systems Inc. (2006)

Urba A, Kvietkus K, Sakalys J, Xiao Z, Lindqvist O. A new sensitive and portable mercury vapor analyzer GARDIS-1A. InMercury as a Global Pollutant 2008 (pp. 1305-1309). Springer Netherlands

Rosencwaig A, Gersho A. Theory of the photoacoustic effect with solids. Journal of Applied Physics. 1998 Jan;47(1):64-9.

KOPYsc E, PYRZYnska K, Garbos S, BULSKA E. Determination of mercury by cold-vapor atomic absorption spectrometry with preconcentration on a gold-trap. Analytical sciences. 2000;16(12):1309-12

Questions previously asked

Discuss role of mercury in dental amalgam and add a note on mercury hygiene.

(20 marks, RGUHS 2001) Concerns about mercury toxicity. (7 marks, NITTE 2013) Discuss mercury toxicity in dental office. (10 marks, RGUHS 2007) Discuss in detail on hazards of mercury. (20 marks, RGUHS 2008)

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Mercury in Restorative Dentistry

Health & Medicine