Prof. Asaad Javaid
MDS
DEPT OF RESTORATIVE DENTAL
SCIENCES
COLLEGE OF DENTISTRY, ZULFI
ALMAJMA UNIVERSITY
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
Chemical Forms of Hg
• Elemental
• Inorganic
• Organic
Hg
(Mercury)
Hg-S
(Cinnabar)
Hg-(CH3)2 (Dimethyl Mercury)
Absorption routes



Elemental
Inorganic
Organic
Skin
-------------
Lungs
80 %
80 %
-----
GI Tract
0.01 %
7%
95-98 %
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
 Clinic staff
Dentist
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
http://www.quackwatch.org/01QuackeryR
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
THANK YOU