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2
*
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*
*Dental Amalgam is a metal like restorativematerial composed of a mixture of
silver/tin/copper alloy and mercury.
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*
Dimensional change
Strength
Corrosion
Creep
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*
Ideally, an amalgam should have:
No change in dimensions
Remain stable for the life of the restoration.
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Ideally the dimensional change should be small
Severe contraction:-
Microleakage Plaque accumulation
Secondary caries
Excessive expansion :-
Pressure on the pulp
Postoperative sensitivity
Protrusion of restoration
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ANSI/ADA SPECIFICATION NO 1
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ANSI/ADA SPECIFICATION NO.1
Amalgam neither contract nor expand morethan 20 m /cm measured at37degcelsius
Between 5 min and 24 hr after the beginningof triturition .
With a device that is accurate to at least0.5m
The specimen size should be essentiallyequivalent to the bulk used in large
restorations 7
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*
The leading causes for failures include
Secondary caries
Marginal fracture
Bulk fracture
Tooth fracture
At microstructural level
Corrosion & tarnish
Transformation
Stress associated with mastication forces
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*
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*
*Under triturition
Restoration in the mouth has contracted orexpanded within the required 20micrometers
limit of such dimensional change .As average human hair is 40micrometer it isvirtually impossible to detect margins that may
be open a a few micrometers either wit a eye
or dental instrument
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*
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*
*Early surveys 16.6% of a large group ofdefective restoration failed because of
excessive expansion.
There are several causes of excessive
expansion
*1.Delayed expansion
*2.Insufficient triturition or condensation
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*In delayed expansion large expansion
begins after 4-5 days following
condensation
*Patient may experience pain after 10-12
days after the insertion of the restoration
.
*Assumed that when a expansion of thin
magnitude occurs ,the restoration maybecome wedged so tightly against the
cavity walls that a pressure towards the
pulp chamber results and finally
protrusion of restoration.11
*
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*If the patient complains of pain after 1 day after
a restoration is placed cannot be suffering from
delayed expansion
Shiny abrasion marks
Possibility of hyper occlusion
Occlusion should be adjusted12
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*
oPrimary requisite- sufficiently high strength to
resist fracture.
oFracture of even a small area , especially at the
margins , increases the risk for corrosion ,
secondary caries , &subsequent clinical failure.
oMargin defects are the most frequently defects in
amalgam.
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*
Compressive strength of a satisfactory amalgam should be 310MPacompressive strength tensile strength
(MPa) (MPa)
Amalgam 1hour 7days 24hour
Low copper 145 343 60
Admix 137 431 48
Single 262 510 64
composition
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*
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*EFFECT OF TRITURATION:- The type of amalgam alloy
-the trituration time
- speed of the amalgamator
so either undertrituration or overtrituration decreases the strength in bothtraditional &high copper amalgam.
*EFFECT OF CONDENSATION:-condensation pressure
-technique
-alloy particle
Lathe cut alloy- high condensation pressure.
Spherical alloy- light pressure.Good condensation techniques express mercury result in asmaller volume fraction of matrix phases .
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*
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*Effect of porosity:- due to plasticity of the mix .
plasticity decreases increase in time
undertrituration & delayed condensation
*Effect of amalgam hardening rate: probably a high % of
restorations that fractures do shortly after insertion. Clinical
manifestation may not be evident but an initial crack mayoccur within few hours.
At the end of 20 min , compressive strength may be only 6% ofthe 1- wk strength .
ANSI/ADA specification stipulates a minimum compressivestrength of 80 MPa at 1hr.
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*
*Any exccess mercury left in the restoration can produce a
marked reduction in strength.
*Mercury content increases more than app. 54% than the
strength is markedly reduced .
*Low mercury amalgam contain more of stronger alloy particles
&less of weaker matrix phases.*But increasing the final mercury content increases the volume
fraction of the matrix phases at the expense of the alloy
particles .
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**Amalgam restorations often tarnish &corrode in the oral
environment.
*Degree of tarnish and the resulting discoloration depends
greatly on the individuals oral environment & to a certain
extent to the alloy employed.
*Active corrosion of a newly placed restoration occurs on the
metal surface along the interface between the tooth and the
restorations .
*Self sealing restorations .
*Presence of2
Most common products oxides &chlorides of tin
If gold restoration is placed in contact with an amalgam .18
*
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**DEFINITION:-time dependent plastic strain of a material under a static load or
constant stress.
* Creep has been found to correlate with the marginal breakdown of traditional low
copper amalgams.
Higher the creep Greater degree magnitudeof marginal deterioration.
It is prudent to select a commercial alloy that
has a creep rate below the level of 3%
specified in ANSI/ADA specification no. 1 .
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*Low copper - 2.0%
*Admix - 0.4 %
*Single composition - 0.13%
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I fl f i t t
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Influence of microstructure on creep:-
phase has a primary influence on low copperamalgam creep rates .
*Creep rates - higher volume fractions .
*Creep rate - larger grain sizes.
Presence of2 - higher creep ratesVery low creep rates in single composition high copper alloys
which may be associated with rods .
Effect of manipulative variables on creep-
Mercury alloy ratio should be minimized .
Condensation pressure maximized for lathe cut & admixedalloys .
1
1
1
21
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FOUR MAJOR MANIPULATIVE
VARIABLES OF SILVER AMALGAM
1. The proportioning of mercury and alloy
2. Trituration
3. Condensation
4. Contouring and finishing
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*
*Historically only way to achieve smooth & plasticamalgam mix is by considerable amount of mercury .
*Because of deleterious effects mercury contents
are reduced
For conventional mercury 2 Techniques were used1. Removal by squeezing & wringling.
2. During condensation
But there is considerable chance of error .
So the most obvious method is to reduce the mercurycontent by reducing mercury alloy ratio.
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i i i i d i d
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Minimal mercury technique or Eames technique- designed
for manipulation with reduced mercury/alloy ratios .
Sufficient mercury should be present in the original
mix to provide a coherent & plastic mass aftertriturition but it should be as minimal as kept.
Mercury content of the finished restoration shouldbe comparable of that of the original mercury alloy,usually about 50% with lesser amounts
(~42wt%)being used with spherical alloys.
Excellence of clinical restorations
Proper
manipulation24
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*Amount of alloy & mercury mercury/alloy ratio
*Acc. to ratio
Mercury /alloy ratio 6 parts of mercury
of 6/5 indicates 5 parts of alloyby wt.
*According to percentage
a mix of amalgam prepared with a mercury / alloy ratio of6:5 contains 54. 5% of mercury .
Recommended mercury/alloy ratios :-
Lathe cut alloys - 1:1 or 50% mercury
Spherical alloys 42%
If Mercury content low Mix can be dry and grainy .
- Corrosion resistance is reduced .25
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Disposable capsules
*Pre-proportioned aliquots of mercury &alloy.
*Contain alloy powder either in pellet formor as pre-weighed portion of powder inconjunction with appropriate quantity ofmercury.
Separated from each other to preventamalgamation.
Self activating capsules.
Eliminates the chance of mercury spills duringproportioning.
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**Its objective is to wet all the surfaces of the alloy
particles with mercury.*For proper wetting ,the alloy surface should beclean .
*Rubbing of the particles mechanically removes
the oxide film coating on alloy particles.
*Trituration is achieved either by:-
*1. Hand mixing
*2. Mechanical trituration
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*
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*
Glass mortar &pestle are used.
Glass mortar inner
surface roughened toincrease the frictionbetween amalgam andthe glass surface .
Pestle is a glassrod with a round end.
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Three factors to obtain a well mixed amalgam mass are
1. Number of rotations
2. Speed of rotation
3. Magnitude of pressure placed on
the pestle.
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*
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*
*Mechanical amalgamators are more
commonly used to triturate amalgam alloy& mercury.
*CAPSULE mortar
*PISTON pestle
*Capsule is inserted between the arms ontop of the machines . When put on, the
arms holding the capsule oscillate at high
speed , thus triturating the amalgam .
*Newer amalgamators have hoods toconfine mercury spray & prevent
accidents .
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*
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*Mixing time
refer to manufacturerrecommendation.
Spherical alloys usually require lessamalgamation time than do lathe
cut alloys.
A large mix requires slightly longer
mixing time than a smaller one .
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ADVANTAGES :-
1.Shorter mixing time .2. More standardized procedure.
3. Requires less mercury as compared
to hand mixing technique.
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NORMAL MIX
Shiny surface & a smooth & soft consistency.
Warm but not hot when removed from the capsule .
Best compressive strength & tensile strength .
Have increase resistance to tarnish and corrosion.
OVERTRITURATION
Hot mix.
Mix is soupy & sticks to capsule.
Decreases working / setting time.
Slight increase in setting contraction.
Creep is increased.33
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UNDERTRITURATION
Grainy, crumbly mix.
Rough surface after carving .
Strength is less .
Mix hardens too rapidly.
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*Actually a continuation of triturition .
-Improve the homogenecity of the mass.
-To assure a consistent mix
it can be accomplished in 2 ways:-
1. Mix is enveloped in a dry piece of rubber dam &
vigrously rubbed between the 1st finger & the thumb ;or the thumb of one hand &palm of the other hand .
The process should not exceed 2 to 5 seconds .
2. After trituration the pestle can be removed from the
capsule , & the mix can be triturated in the pestle-free capsule for an additional 2 to 3 seconds .
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*
GOAL- To compact the alloy into the prepared cavity
so that the greatest possible density is attained ,
with sufficient mercury present to ensure complete
continuity of the matrix phase between the alloy
particles.
It is of two types :-
1. Hand condensation.
2. Mechanical condensation.36
*
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*Increments should be carried to &inserted into the
prepared cavity by means of instruments such as anamalgam carrier.
Once placed , should be immediately condensed toremove voids & adapt to the marginal walls .
Condensation is usually started at the centre & thenthe condenser point is stepped little by little towards
the cavity walls.
After condensation of an increment, the surfaceshould be shiny in appearance.
37
*
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*
The procedure of adding an Increment ,condensing it
, adding another increment & so forth is continueduntil the cavity is overfilled .
Any mercury-rich material at the surface of the lastincrement , constituting the overfill, is removed when
the restoration is carved.
Most important factor- size of the amalgamincrement carried into the cavity . Larger the piece
,more difficult to reduce the voids & adapt it to the
cavity walls.
38
*
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*
The condensation pressure isgoverned by
1. The area of the condenserpoint, orface.
2. The force exerted on it by theoperator .
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Smaller the Increased pressure
Condenser is exerted on the
amalgam
Thrust of 44(N)(10lb)
Circular Condenser 2mm 13.8mpa
(2000psi)
Circular Condenser 3.5mm 4.6mpa
(667 psi)
40
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Force recommended 66.7N
For condensation (15lb)
But forces applied 13.3N-17.8N
Generally (3-4lb)
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Oval
Crescent
Trapezoidal
Square
Round condenser
Triangular
Rectangular point
42
*
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**The procedures and principles of mechanical
condensation are the same as those for handcondensation.
* The only difference is that the condensation of the
amalgam is performed by an automatic device.
* Various mechanisms are employed for these instruments.
Impact type of force
Rapid vibration.
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Advantages:
1. Whichever device , less energy is needed thanfor hand condensation2. The operation may be less fatiguing to the
dentist .
Similar clinical results
The method selected is usually based on thepreference of the dentist.
44
*
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** After condensation , the restoration is carved to
reproduce the proper tooth anatomy.
OBJECTIVE-
* To simulate the anatomy rather to reproduce
extremely fine detail.
*Carving is too deep- Bulk at marginal areas are reduced.
Thinning will leads to its fracture undermasticatory forces .
* Craving should not be started until the amalgam is hard
enough to offer resistance to the instrument.
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*
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After the carving is completed the surface should be
smoothed .This may be accomplished by judiciouslyburnishing the surface &margins of the restoration.
Burnishing of the occlusal anatomy can be accomplishedwith a ball burnisher .
* A rigid, flat bladed instrument is best used on smoothsurfaces.
* Pre-burnish
* removes excess mercury
* improves margin adaptation
* Post-burnish
* improves smoothness
46
*
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*Final smoothing Moist cotton pellet
Done b y rubbing or
The surface Rubber polishing cup
with prophylactic paste
Final finish of the restoration should not be done until
the amalgam is fully set.
It should be delayed for 24hr after condensation.
The use of dry polishing powders can raise the surfacetemperature above the 60deg c (danger point).
Thus a wet abrasive powder in a paste should be used.
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*Toxicology is derived from greek word toxicon (arrowof poison) and logus (knowledge). It is the study ofadverse effects of chemicals on living organisms.
*Mercury is a liquid metal.
*Any alloy in presence of mercury forms amalgam,which forms a plastic mass which is inserted and
finished in the prepared cavity.
*Patients can be exposed to mercury, by release of itsvapor from amalgam fillings.
*
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**Mercury toxicity from dental restorations is the cause for certain
undiagnosed illness, and a real hazard may exist for dentist whenmercury vapor is inhaled during mixing, placement and removal.
*Mercury penetrates from the restoration into tooth structureleading to discoloration of the tooth.
*Small amounts of mercury are released during mastication.
*Most significant contribution to mercury assimilation from dentalamalgam is via vapor phase.
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* Mercury release from amalgam fillings is phasic andconsists of a very low release, and an increasedstimulated release results due to tooth brushing orchewing.
* Mercury emitted from amalgam may be in one or twoforms.
* Mercury vapor(hg0) which passes into intra oral airand from here may be either inspired into the lungsor expired into the outside air.
* Mercuric ions (hg2+)which passes into the saliva andfrom there to the gastro intestinal tract.
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*Dentists are exposed daily to the risk of mercuryintoxication,through skin,or by inhalation.
*Mercury vapor has no color, odor, or taste and cannot bereadily detected by simple means.
*As liquid mercury is almost 14 times more dense thanwater in volume it becomes very significant.
* Maximum level of occupational exposure considered
safe is 50g of mercury per cubic meter of air.
*
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AUTHOR NO. OF
SURFACES
MERCURY(g/
DAY)VIMY &
LORSEHEIDER(1985)
12.6 19.8
LANGWORTH(1988)
25 3
SNAPP (1989) 14 1.3
SKARE &ENGQVIST
(1994)
39 12
*
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*
*VAPOR METALLIC hg CAN BE INHALED AND ABSORBEDTHROUGH THE ALVEOLI IN THE LUNGS AT 80%EFFICIENCY, AND THUS CONSIDERED AS THE MAJORROUTE FOR ENTRY INTO HUMAN BODY.
*Concentrates in certain organs such as liver, kidney andbrain.
*Eventually all are excreted but rate is dependent uponbodys ability to convert it to other forms.
*
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INVESTIGATOR CHEWING/
BRUSHING
BEFORE
AFTER UNITS
SVARE(1981)
0.88 13.74 g/cubicmeter
OTT et
al(1986)
0.29 1.35 g/cubic
meter
VIMY
(1985)
4.91 29.10 g/cubic
meter
*
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*
EFFECT FOOD AND DRINK
NO EFFECT HOT AND COLD DRINK,APPLE
DECREASE MIXED LUNCH,EGGS
INCREASE BRITTLE BISCUITS
AVERAGE STIMULATION FACTORS
GUM CHEWING X 5.3
MIXED FOOD CHEWING X 3.7
TOOTH BRUSHING X 1.9
*
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*
SUBJECTS CONC.INTISSUES(ng/g)
KIDNEYMEAN(n)
PITUITARYn
BRAINn
DENTISTS
(3)
1533 1599 61
CONTROL
(12)
273 107 11
*
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*
*CLINICAL MERCURISM THRESHOLD -100g per cubicmeter.(Loael low observed adverse effect level)
*Nephrotoxicity threshold -50g per cubic meter.(Loael)
*World health organization industrial threshold -25g percubic meter.(Noael no observed adverse effect level)
*General public threshold -5g per cubic meter.(Noael)
*Children,pregnant,sick threshold -1g per cubicmeter.(Noael)
*
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*Vimy/lorscheider (am jphysio 1990/258/939-945)
* 5 adult ewes autopsied
after amalgam placement.
*3-5 fetal lambs exposed inutero after mothers amalgamplacement.
* 80 Wi t R t E d 40 t H 0 d
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* 80 Wistar Rats Exposed: 40 to Hg0, and
40 to Hg0 + chlorine vapors (P L VIOLA ANDCASSANO AUTORADIOGRAPHIC STUDY 1968/59/437-44)
*AFTER 6 WKS OF EXPOSURETO hgo RATS REVEALEDHYPEREXCITEMENTSOMETIMES FOLLOWED BYATAXIA AND TREMOR WHILETHE RATS EXPOSED TO
BOTH SHOWED MILDDYSPNOEA,COUGH ANDDIARRHOEA.
*After 8 wks 10 out of40 ratsdied in 1st group and 4 out40 died in 2nd group.
* Pink Disease: the iatrogenic poisoning of babies
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Pink Disease: the iatrogenic poisoning of babieswith mercury-containing teething powders &
worming medicines
*Warkany ( am j dis child 1966/112/147-156) estImatedthat 1 in 500 exposed infantsdeveloped the disease.
* For over a hundred yrs thousands
of children were killed byaccidental poisoning and manysuffered in misery.
*Disease disappeared after the Hgcontaining medicine were withdrawn. Adult survivors of pink
disease tend to have aspergerssyndrome.
*
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**Mad as a hatter" will forever be linked to the madcap
millionaire in Lewis Carroll's classic children's book, Alice in
Wonderland.
*But few actually know that the true origin of the sayingrelates to a disease peculiar to the hat making industry in the1800s.
*A mercury solution was commonly used during the process ofturning fur into felt, which caused the hatters to breathe inthe fumes of this highly toxic metal.
*Resulting in symptoms such as trembling (known as "hatters'shakes"), loss of coordination, slurred speech, loosening ofteeth, memory loss, depression, irritability and anxiety --"The Mad HatterSyndrome."The phrase is still used today
to describe the effects ofmercury poisoning.
*Hg poisoning induces a wide range of
http://www.newstarget.com/depression.htmlhttp://www.newstarget.com/anxiety.htmlhttp://www.newstarget.com/depression.htmlhttp://www.newstarget.com/anxiety.htmlhttp://www.newstarget.com/mercury_poisoning.htmlhttp://www.newstarget.com/mercury_poisoning.htmlhttp://www.newstarget.com/mercury_poisoning.htmlhttp://www.newstarget.com/mercury_poisoning.htmlhttp://www.newstarget.com/anxiety.htmlhttp://www.newstarget.com/depression.html7/27/2019 Zia Seminar
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Hg poisoning induces a wide range ofpsychiatric disturbances
* GERSTNER AND HUFF JOURNAL OF TOXICOLOGY AND ENVIORNMENTALHEALTH 1977/2/491-526
*Exposed persons experience feelings of fatigue andrestlessness; they lose interest in their surroundings andin their own life; they withdraw more and more fromsocial contacts; they become increasingly irritable and
sensitive, reacting strongly to relatively innocent remarksuttered by family or friends; and they have a tendency forsweating and blushing. In this blushing - or reddening -the classical term "erethism finds its origin.
* In very severe cases, the depression may reach suicidalproportions.
* A deterioration of intelligence gradually emerges duringchronic exposure to elemental mercury. Previously brightpersons become dull and slow in thinking.
* Experts Agree: Its an Intriguing
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p g g gNeurotoxin.Nothing else even comes close!
CLARKS JOURNAL OF TRACE ELEMENTS IN EXPERIMENTALMEDICINE 1998/11/303-317
Inhaled mercury vapor produces a range of fascinating and bizarrechanges in human behavior.
Erethism is a wide spectrum of psychological and personalitydisturbances. One end of the spectrum involves delirium,hallucinations, excessive shyness, and fits of rage. . . [while]irritability, insomnia, and lassitude may be the lower end of theerethism spectrum.
No other metal can affect the central nervous system in this way.In fact, it is doubtful that any chemical, even hallucinogenic drugs,can compare with mercury vapor. It is a tantalizing problem to theneuroscientist.
*
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*
*This at times been claimed aspotential hazard. This is an immunesystem response to very low level ofmercury.
*The antigen antibody reaction marksby itching, rashes, sneezing, difficultyin breathing, swelling, or othersymptoms.
* Delayed hypersensitivity to mercuryresults in a contact eczematousreaction on the skin and possibly the
oral mucosa.
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*Its prevalance is low in population. Only 41published cases of allergy to amalgamrestoration from 1905-1986. Oralmanifestations were present in only 17cases.
*When such a reaction has beendocumented, an alternative material, suchas composite, ceramic or cast metal alloymust be used.
*What is a safe level of
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vapor?
*The U.S. Environmental ProtectionAgency sets a non-occupationalreference air concentration (RfC).In 1996, the RfC was:
0.300 g Hg0
/m3
*The U.S. Agency for Toxic Substancesand Disease Registry (ATSDR) publishesa Minimal Risk Level (MRL) for non-occupational exposure. In 1999, the
MRL for mercury vapor was set at:0.200 g Hg0/m3
*
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*Mercury is the most toxic non-radioactive element onearth.
*A silver-coloured mercury amalgam filling normallycontains 52 percent mercury.
*On average, amalgam fillings weigh 1 gram and contain gram of mercury.
*Half a gram of mercury in a 10-acre lake would warrantissuance of a fish advisory for the lake.
*1 OUT OF EVERY 10 DENTAL OFFICE CROSSES THE MAX.
EXPOSURE LEVEL OF MERCURY.
*SO WHY ARE DOCTORS
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SO WHY ARE DOCTORSAVOIDING IT?
There have been epidemics of mercurypoisoning among wildlife and human populationsin many countries. With very few exceptions andfor numerous reasons, such outbreaks weremisdiagnosed for months or even years. Reasonsfor these tragic delays included the insidiousonset of the affliction, vagueness of earlyclinical signs, and the medical profession'sunfamiliarity with the disease.
HARDMAN J G,LIMBIRD L ETHEPHARMACOLOGICAL BASIS OFTHERAPEUTICS,10THEDITION,MC GRAW HILL -2001
*
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*Chelation was first used in the 1940s by the U.S. Navy to treat leadpoisoning and was subsequently approved by the FDA as a safemethod of treating heavy metal toxicity. Chelation therapy is amedical treatment that improves metabolic and circulatory functionby removing toxic metals and abnormally located nutritional metallicions (such as iron) from the body. This is accomplished by
administering an amino acid, ethylene-di- amine-tetra-acetic acid(EDTA), by either an oral or intravenous infusion.
*When a molecule of EDTA travels through the blood stream, it grabson to the heavy metal particles, binding tightly and pulling them out
of the membrane or body tissue in which they are embedded. SinceEDTA is an artificial amino acid, the body regards it as a foreignsubstance and delivers it to the kidneys to be excreted in the urine.
*
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MAIN AREAS THAT BEEN INVESTIGATED ARE
*CNS
*RENAL SYSTEM
* IMMUNITY
*ORAL CAVITY
*BIRTH DEFECTS
*GENERAL HEALTH
*
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* THE MINIMUM URINARY LEVEL TO SHOW ANY SIGN OFNEUROTOXICITY IS 25/g CREATININE AND THIS IS 6 TIMESHIGHER THAN HIGHEST URINE LEVEL ATTRIBUTABLE TOPRESENCE OF DENTAL RESTORATION.
*A recent study in greenland (tulinus -arctic medicalresearch 1995/54) showed intellectual ability of schoolchildren with dental amalgam restoration in their mouth.
*No corelation found in marks in any shool subjects and
no.Of amalgam restoration.
* So no relationship between the presence of amalgamfillings and neurological function.
*
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72
*
* Studies of industrial workers exposed to mercury show thataltered kidney dysfunction does not occur until the urinemercury level is more than 25 times higher than thatassociated with dental amalgam fillings.
* Studies on humans by weismann and hoffmannn (pharmaco
toxicology 1995/76/47-49) showed no evidence of kidneyimpairment after measuring urine mercury and n acetyl p-glucosaminidase (nag) levels in 100 subjects.
* In 66 subjects dental restorations were present and 34 subjectswere without fillings. No significant difference between thegroups.
* So no evidence linking dental amalgam with kidneydysfunction.
*
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*Studies by wilheim,dunninger (clinical investigation -1992/70/728-734) compared 2 patient groups,1 havingamalgam fillings for 1st time other having all existingamalgam fillings removed.
*The relative no. Of t- lymphocytes, b lymphocytes weredetermined before and after these treatments.
*No difference between 2 groups and no effects ofamalgam fillings on any white blood cells orimmunocompetence.
*
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* Study showed by summers and wireman (antimicrobial agents chemotherapy 1993/37/825-834),changes in antibioticresistance of oral and intestinal bacteria in monkeys with 12 amalgam restoration for 5 weeks did not show anychange in the pattern of antibiotic resistance to these bacteria.
* This was because there were a large no. Of antibiotic resistant bacteria present in the gut both before and after thisexperiment.
* No evidence to support that mercury from amalgam fillings can increase the no. Of antibiotic resistant bacteria inthe mouth or gut
*
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*Human studies (kuntz d,pitkin american journal obstestrics gynaecology-1982/143/440-443) attempted to relate still birth and birth defect tomercury level in maternal and umbilical cord blood.
* No significant association with the no. Of amalgam fillings in themothers.
* Ada survey of dentists and dental nurses(brodshy and cohen jada
1985/111/779-780) found no difference in the rates of spontaneousabortion and fetal abnormalities in subjects exposed to high low level ofmercury.
* No association between amalgam fillings and birth defects.
*
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*A large survey was conducted on 1024 subjects(aged 38-72 by ahlgwist and bengtssoncdoe/1988/16/227-231) by questioning on specificsymptoms and complaints to the no. And size ofamalgam restoration in their mouth.
*No corelation were found between them insteadthose with dental amalgam fillings showed bettergeneral health than those without fillings probablyreflecting greater concern for health matters.
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*
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* SYMPTOMS KNOWING POTENTIAL HAZARDS, eg SENSITIVITY ANDNEUROPATHY
* Hazards - potential sources of mercury vapor, eg spills, leakydispensers,polishing and removal of amalgams,heating ofcontaminted instruments.
* Ventilation proper ventilation in work place by having fresh airexchanges and periodic replacement of filters which may trapmercury.
* Monitor office the mercury vapor level should be periodicallymonitored by dosimeter badges.THE CURRENT OSHA LIMIT FORMERCURY VAPOR IS 50 gm/cubic meter IN ANY 8 HR WORK SHIFTOVER A 40 HR WEEKLY WORK
*
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*Monitor personnel periodic analysis (avg.Mercury level in urine is6.1g/lt FOR DENTAL OFFICE PERSONNEL.
* Office design proper work area design to facilitate spill containmentand clean up.
* Precapsulated alloys to eliminate the possibility of a bulk mercury spillor store mercury in unbreakable containers.
* Amalgamator cover it should be fitted with a cover.
*
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*Handling care avoid skin contact with mercury orfreshly mixed amalgam.
*Evacuation system high volume evacuation when
finishing or removing amalgam. Evacuation systemsshould have traps or filters,check clean or replacetraps and filters periodically.
*Masks change mask more often when removingamalgam.
*
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*Recycling store amalgam scrap under radiographic fixersolution in a covered container.
* Contaminated items dispose of mercury contaminateditems in sealed bags according to regulations.
* Spills clean up spilled mercury by using trap bottles,tapesor fresh mixes of amalgam to pick up droplets or use
comercial clean up kits.
* Clothing wear professional clothing in dental operatory.
*
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*Dental amalgam raw materials being stored for use.
* Mixed but unhardened dental amalgam during trituration,insertion,intraoralsetting.
* Dental amalgam scrap that has insufficient alloy to completely consume themercury.
* Dental amalgam undergoing finishing and polishing operations.
* Dental amalgam restoration being removed.
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*
*
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*Glasses, mercuryfilter and mouthmasks should be used.
*Routine exposurebadges should be worn
as recommended byosha.
*
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*In plastic wrappingpackages leakage ispossible.
*Stored in closets orcabinets.
*Storage location should benear a vent that exhaustsair out of the building.
*
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*During triturationsmall amount of
material escape.
*To minimize thisprecapsulated
capsules of alloy and
mercury are available.
*
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*DURING TRITURATION HIGHFREQUENCY CAN FORCE hgRICH MATERIAL OUT TO CREATEAEROSOL OF LIQUID DROPLETSAND VAPOR.
*To minimize this amalgamatorwith covers are preferred.
*To reduce mercury content,reduced mercury : alloy ratio,known as minimal mercury oreames technique is used.
*
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*Small droplets thatspill on floor or
carpets are best
advised to deal with
help of a vacuum
aspirator.
*
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*The scrap after condensation should be collected andstored under water,glycerine or x-ray fixer in a tightlycapped jar, which should be almost filled with liquidto minimize the gas space where mercury can collect.
*No more than a small jar of material should be presentin the office at any time.
*Once dental amalgam is solidified mercury is tightlybound but can be easily liquified during polishingprocedures that generate heat when adequate coolingwater is not used.
*
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*THE Ag Hg PHASE IS MELTED PRODUCING A
MERCURY LIQUID RICH PHASE THAT IS EASILY
SMEARED OVER DENTAL AMALGAM SURFACE
MAKING IT LOOK BRIGHT AND SHINY.
*It is deceptive to the dentist as he can
misinterpret this appearance as a highlypolished surface.
*
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* It is common where high speed
burs contact tooth structure,increase of temperatureleading to release of mercuryvapors.
*Rubber dam, high volumeevacuation and water coolingshould be used to control thissituation.
*
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*
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*Instruments which are used for inserting,finishing, polishing or removing dentalamalgam restoration contain someamalgam material on their surfaces.
*During sterilization techniques mercuryvapors are released on heating so properisolation or venting the air from
sterilization areas should be done.
*
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*Capsules and mercury contaminated cotton rolls or papernapkins should not be thrown out in regular trash. They
should be kept in separate plastic containers for disposal.
*
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*Best non mercury alternative.
*It has similar atom structure and characteristics to mercury.
*Used in the same manner as mercury based amalgam.
*They are 16 times more expensive than similar amount ofmercury based amalgam.
*It is sticky so used by teflon instruments.
*Has high level of corrosive properties.
*
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*Metal alloys (gold)
The only real alternative to amalgam in moderate
to large cavities.
Demands high levels of clinical and lab skills in
fabrication.
Costs 7 -8 times the amount of an equivalent
amalgam restoration.
*
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* Glass ionomer cement* Composite resins
* Glass ionomer resin hybrids
* Compomers
* Ceramics
* Ormocers
used in restoring anterior and cervical cavities in primary and permanent
teeth and restorations of posterior teeth of primary dentition.
All these have shorter life span than amalgam.
AMALGAM FAILURES
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*
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* Inadequate condensation
* Material pulling away or breaking from the
marginal area when carving bonded amalgam
*Potential solutions include:
*Proper condensation technique
*Careful carving of marginal areas, especially
bonded amalgam restorations
*
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*
* Causes of marginal ridge fractures:* Axiopulpal line angle not rounded in Class II tooth
preparations
*Marginal ridge left too high
*Occlusal embrasure form incorrect
* Improper removal of matrix
*Overzealous carving
* Potential solutions include:
* Proper rounding of axiopulpal line angles in Class II tooth
preparations* Creating marginal ridge height correctly, with both the
adjacent tooth and occlusion
* Creating an occlusal embrasure form that mirrors the
adjacent tooth
*
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*Causes of amalgam scrap and mercury
collection and disposal problems include:
*Careless handling
* Inappropriate collection technique
*Potential solutions include:
*Careful attention to proper collection and
disposal
*
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* Amalgam has been used in clinical dentistry for about 200 years.
* Approximately 22 million amalgam restorations are placed eachyear in united states.
* However in continuing to use amalgam, dentists should observestrict mercury and amalgam hygiene procedures in their practicesso that the health of dental workers is not put at risk.
* Enviornmental contamination from dental practices should cutdown to low levels or this could be the main reason for governmentaction against the use of amalgam in the future.
*
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*THERE IS A PRINCIPLEWHICH IS PROOF
AGAINST ALL
ARGUMENT, AND
WHICH CANNOT FAIL
TO KEEP MAN IN
EVERLASTING
IGNORANCE.