DEPT OF RESTORATIVE DENTAL SCIENCES COLLEGE OF DENTISTRY, ZULFI ALMAJMA UNIVERSITY Prof. Asaad Javaid MDS

Mercury in Amalgam restorations

Learning objectives Explain the controversy on use of Hg in amalgam Mention various forms of mercury Describe the absorption route of mercury Describe why Hg can not be released easily from set amalgam Mention permissible Hg -vapor absorption limit for a person List various means of exposure to Hg

Learning objectives Mention adverse effects of Hg Explain why mercury used in dental amalgam in safe List and practice precautions for Hg handling and use

Dental amalgam An alloy of silver-tin with mercury as an essential constituent

Mercury A metal in liquid form

Elemental Hg(Mercury) InorganicHg-S(Cinnabar) OrganicHg-(CH 3 ) 2 (Dimethyl Mercury) Chemical Forms of Hg

Absorption routes SkinLungsGI Tract  Elemental %0.01 %  Inorganic %7 %  Organic %

A set amalgam restoration

Release of Hg from set amalgam In set dental amalgam, the Hg mixed with alloy resides only in the matrix phase (predominantly Ag-Hg) and not in the particles of unreacted alloy The matrix melts at 128C i.e. above the boiling point of water, so it is not easy to melt dental amalgam and release Hg from the matrix phase

Vapor limit Once Hg is released as vapor it can be breathed and absorbed into human body and Persons who are exposed to Hg vapor may display a toxicity or sensitivity reaction Maximum permissible vapor limit is 50 µg/m3 The level is extremely small (5 ppb) Therefore, there is no practical worry for anyone in dentistry in this regard

A time-tested material Amalgam has been successfully and widely used as a filling material since 200 years

Anti-amalgam propaganda Huggins in 1970 claimed that mercury in amalgam is a toxic material He advocated to discontinue the use of amalgam as restorative material

Why to worry with mercury?

Mercury may cause Cardiovascular diseases Nervous system diseases Multiple sclerosis Alzheimer's disease Contact dermatitis Mercury poisoning Allergies

Who could be affected??

Contd… Patient Dentist Clinic staff Dental Assistant Dental hygienist

How exposure to Hg Occurs??

Patients’ exposure It may occur through restorations

Dental staff exposure It occurs through amalgam raw materials being stored for use mixed but unhardened amalgam during trituration, insertion, and intraoral hardening

Contd… amalgam scrap that has insufficient alloy to completely consume the mercury present amalgam undergoing finishing and polishing operations amalgam restorations being removed

Allegations against mercury

Contd… Mercury is toxic Hypersensitivity As liquid/vapor, mercury can be absorbed through the lungs liquid mercury changes into methyl mercury by microorganisms in the mouth or gastrointestinal tract

Truth about Hg in amalgam

Toxicity ?? Dose makes a poison Even table salt can be poisonous No component of set dental amalgam is a known poison

Hypersensitivity Some cases of hypersensitivity to amalgam restorations have been reported The condition seems to be rare and may be of a transient or of a persistent nature (Urbanczyk 2002) Hypersensitivity may occur with any restorative material

Inhalation of mercury

Liquid mercury Mercury is highly volatile in liquid form and may be inhaled in a dental clinic

Safe dispensation The ingredients of current amalgam are sold in pre-proportioned, sealed capsules Neither patients nor dental staff are exposed to the ingredients before they are mixed

Contd… Even if the ingredients were released, the quantities are small and can be readily and safely handled without any risk

Hg in GIT Some times little mercury may be released from amalgam into the oral cavity.Much of this is quickly inactivated by saliva There are no data to show that this mercury is absorbed into the body in a form that may be harmful

Hg present in food and water Amounts of mercury released from amalgam are in the same range as amounts present in our food and water in a regular diet

Contd… FDA, the National Institutes of Health, and the U.S. Public health service have confirmed the safety of amalgam elatedTopics/mercury.html

Should amalgam fillings be replaced?

Removal of serviceable amalgam There is no benefit from removal of amalgam that is clinically sound and serviceable Inappropriate removal of amalgam exposes a patient to an unnecessary procedure

Removal of failed amalgam Use a rubber dam Wear gloves, mask and eye glasses Cover patient’s skin Keep the fillings cool during removal

Contd… Use a high-volume evacuator Immediately dispose off filling particles Remove gloves and clean the patient's mouth

Precautions: to avoid mercury hazards Dental clinic should be well ventilated Excess, waste or scrap amalgam should be stored in water in sealed container

Contd… Mercury or freshly mixed amalgam should not be touched with hands to avoid contact dermatitis Spillage of mercury should be avoided Suitable flooring should be chosen for clinic to deal with accidental spillage of mercury

Contd… Mercury and mercury containing materials should be kept away from heat source Instruments contaminated with mercury should not be sterilized by heat Reusable capsule used with a mechanical amalgamator should have tightly fitting cap to avoid mercury leakage

Contd… During cutting of amalgam, water spray and suction should be used Use of ultrasonic amalgam condenser is not recommended

Contd… Train all your staff involved in handling of mercury or amalgam about hazards of mercury vapors and necessity of mercury hygiene Tell them all the possible sources of mercury vapors in a dental clinic

Contd… Remove professional clothing before leaving the dental clinic

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