Top Banner

of 103

Zia Seminar

Apr 14, 2018

Download

Documents

Shipra Singh
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
  • 7/27/2019 Zia Seminar

    1/103

  • 7/27/2019 Zia Seminar

    2/103

    2

    *

  • 7/27/2019 Zia Seminar

    3/103

    *

    *Dental Amalgam is a metal like restorativematerial composed of a mixture of

    silver/tin/copper alloy and mercury.

    3

  • 7/27/2019 Zia Seminar

    4/103

    *

    Dimensional change

    Strength

    Corrosion

    Creep

    4

  • 7/27/2019 Zia Seminar

    5/103

    *

    Ideally, an amalgam should have:

    No change in dimensions

    Remain stable for the life of the restoration.

    5

  • 7/27/2019 Zia Seminar

    6/103

    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

    6

    ANSI/ADA SPECIFICATION NO 1

  • 7/27/2019 Zia Seminar

    7/103

    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

  • 7/27/2019 Zia Seminar

    8/103

    *

    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

    8

    *

  • 7/27/2019 Zia Seminar

    9/103

    *

    *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

    9

    *

  • 7/27/2019 Zia Seminar

    10/103

    *

    *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

    10

  • 7/27/2019 Zia Seminar

    11/103

    *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

    *

  • 7/27/2019 Zia Seminar

    12/103

    *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

  • 7/27/2019 Zia Seminar

    13/103

    *

    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.

    13

  • 7/27/2019 Zia Seminar

    14/103

    *

    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

    14

    *

  • 7/27/2019 Zia Seminar

    15/103

    *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 .

    15

    *

  • 7/27/2019 Zia Seminar

    16/103

    *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.

    16

  • 7/27/2019 Zia Seminar

    17/103

    *

    *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 .

    17

  • 7/27/2019 Zia Seminar

    18/103

    **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

    *

  • 7/27/2019 Zia Seminar

    19/103

    **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 .

    19

  • 7/27/2019 Zia Seminar

    20/103

    *Low copper - 2.0%

    *Admix - 0.4 %

    *Single composition - 0.13%

    20

    I fl f i t t

  • 7/27/2019 Zia Seminar

    21/103

    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

  • 7/27/2019 Zia Seminar

    22/103

    FOUR MAJOR MANIPULATIVE

    VARIABLES OF SILVER AMALGAM

    1. The proportioning of mercury and alloy

    2. Trituration

    3. Condensation

    4. Contouring and finishing

    22

  • 7/27/2019 Zia Seminar

    23/103

    *

    *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.

    23

    i i i i d i d

  • 7/27/2019 Zia Seminar

    24/103

    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

  • 7/27/2019 Zia Seminar

    25/103

    *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

  • 7/27/2019 Zia Seminar

    26/103

    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.

    26

  • 7/27/2019 Zia Seminar

    27/103

    **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

    27

    *

  • 7/27/2019 Zia Seminar

    28/103

    *

    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.

    28

  • 7/27/2019 Zia Seminar

    29/103

    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.

    29

    *

  • 7/27/2019 Zia Seminar

    30/103

    *

    *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 .

    30

    *

  • 7/27/2019 Zia Seminar

    31/103

    *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 .

    31

  • 7/27/2019 Zia Seminar

    32/103

    ADVANTAGES :-

    1.Shorter mixing time .2. More standardized procedure.

    3. Requires less mercury as compared

    to hand mixing technique.

    32

  • 7/27/2019 Zia Seminar

    33/103

    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

  • 7/27/2019 Zia Seminar

    34/103

    UNDERTRITURATION

    Grainy, crumbly mix.

    Rough surface after carving .

    Strength is less .

    Mix hardens too rapidly.

    34

  • 7/27/2019 Zia Seminar

    35/103

    *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 .

    35

  • 7/27/2019 Zia Seminar

    36/103

    *

    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

    *

  • 7/27/2019 Zia Seminar

    37/103

    *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

    *

  • 7/27/2019 Zia Seminar

    38/103

    *

    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

    *

  • 7/27/2019 Zia Seminar

    39/103

    *

    The condensation pressure isgoverned by

    1. The area of the condenserpoint, orface.

    2. The force exerted on it by theoperator .

    39

  • 7/27/2019 Zia Seminar

    40/103

    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

  • 7/27/2019 Zia Seminar

    41/103

    Force recommended 66.7N

    For condensation (15lb)

    But forces applied 13.3N-17.8N

    Generally (3-4lb)

    41

  • 7/27/2019 Zia Seminar

    42/103

    Oval

    Crescent

    Trapezoidal

    Square

    Round condenser

    Triangular

    Rectangular point

    42

    *

  • 7/27/2019 Zia Seminar

    43/103

    **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.

    43

  • 7/27/2019 Zia Seminar

    44/103

    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

    *

  • 7/27/2019 Zia Seminar

    45/103

    ** 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.

    45

    *

  • 7/27/2019 Zia Seminar

    46/103

    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

    *

  • 7/27/2019 Zia Seminar

    47/103

    *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.

    47

  • 7/27/2019 Zia Seminar

    48/103

    48

    *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.

    *

  • 7/27/2019 Zia Seminar

    49/103

    49

    **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.

  • 7/27/2019 Zia Seminar

    50/103

    50

    * 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.

  • 7/27/2019 Zia Seminar

    51/103

    51

    *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.

    *

  • 7/27/2019 Zia Seminar

    52/103

    52

    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

    *

  • 7/27/2019 Zia Seminar

    53/103

    53

    *

    *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.

    *

  • 7/27/2019 Zia Seminar

    54/103

    54

    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

    *

  • 7/27/2019 Zia Seminar

    55/103

    55

    *

    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

    *

  • 7/27/2019 Zia Seminar

    56/103

    56

    *

    SUBJECTS CONC.INTISSUES(ng/g)

    KIDNEYMEAN(n)

    PITUITARYn

    BRAINn

    DENTISTS

    (3)

    1533 1599 61

    CONTROL

    (12)

    273 107 11

    *

  • 7/27/2019 Zia Seminar

    57/103

    57

    *

    *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)

    *

  • 7/27/2019 Zia Seminar

    58/103

    58

    *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

  • 7/27/2019 Zia Seminar

    59/103

    59

    * 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

  • 7/27/2019 Zia Seminar

    60/103

    60

    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.

    *

  • 7/27/2019 Zia Seminar

    61/103

    61

    **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.html
  • 7/27/2019 Zia Seminar

    62/103

    62

    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

  • 7/27/2019 Zia Seminar

    63/103

    63

    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.

    *

  • 7/27/2019 Zia Seminar

    64/103

    64

    *

    *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.

  • 7/27/2019 Zia Seminar

    65/103

    65

    *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

  • 7/27/2019 Zia Seminar

    66/103

    66

    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

    *

  • 7/27/2019 Zia Seminar

    67/103

    67

    *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

  • 7/27/2019 Zia Seminar

    68/103

    68

    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

    *

  • 7/27/2019 Zia Seminar

    69/103

    69

    *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.

    *

  • 7/27/2019 Zia Seminar

    70/103

    70

    MAIN AREAS THAT BEEN INVESTIGATED ARE

    *CNS

    *RENAL SYSTEM

    * IMMUNITY

    *ORAL CAVITY

    *BIRTH DEFECTS

    *GENERAL HEALTH

    *

  • 7/27/2019 Zia Seminar

    71/103

    71

    * 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.

    *

  • 7/27/2019 Zia Seminar

    72/103

    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.

    *

  • 7/27/2019 Zia Seminar

    73/103

    73

    *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.

    *

  • 7/27/2019 Zia Seminar

    74/103

    74

    * 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

    *

  • 7/27/2019 Zia Seminar

    75/103

    75

    *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.

    *

  • 7/27/2019 Zia Seminar

    76/103

    76

    *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.

  • 7/27/2019 Zia Seminar

    77/103

    21.09.2006 77

    *

  • 7/27/2019 Zia Seminar

    78/103

    78

    * 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

    *

  • 7/27/2019 Zia Seminar

    79/103

    79

    *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.

    *

  • 7/27/2019 Zia Seminar

    80/103

    80

    *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.

    *

  • 7/27/2019 Zia Seminar

    81/103

    81

    *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.

    *

  • 7/27/2019 Zia Seminar

    82/103

    82

    *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.

  • 7/27/2019 Zia Seminar

    83/103

    21.09.200683

    *

    *

  • 7/27/2019 Zia Seminar

    84/103

    84

    *Glasses, mercuryfilter and mouthmasks should be used.

    *Routine exposurebadges should be worn

    as recommended byosha.

    *

  • 7/27/2019 Zia Seminar

    85/103

    85

    *In plastic wrappingpackages leakage ispossible.

    *Stored in closets orcabinets.

    *Storage location should benear a vent that exhaustsair out of the building.

    *

  • 7/27/2019 Zia Seminar

    86/103

    86

    *During triturationsmall amount of

    material escape.

    *To minimize thisprecapsulated

    capsules of alloy and

    mercury are available.

    *

  • 7/27/2019 Zia Seminar

    87/103

    87

    *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.

    *

  • 7/27/2019 Zia Seminar

    88/103

    88

    *Small droplets thatspill on floor or

    carpets are best

    advised to deal with

    help of a vacuum

    aspirator.

    *

  • 7/27/2019 Zia Seminar

    89/103

    89

    *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.

    *

  • 7/27/2019 Zia Seminar

    90/103

    90

    *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.

    *

  • 7/27/2019 Zia Seminar

    91/103

    91

    * 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.

    *

  • 7/27/2019 Zia Seminar

    92/103

    21.09.200692

    *

  • 7/27/2019 Zia Seminar

    93/103

    93

    *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.

    *

  • 7/27/2019 Zia Seminar

    94/103

    94

    *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.

    *

  • 7/27/2019 Zia Seminar

    95/103

    95

    *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.

    *

  • 7/27/2019 Zia Seminar

    96/103

    96

    *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.

    *

  • 7/27/2019 Zia Seminar

    97/103

    97

    * 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

  • 7/27/2019 Zia Seminar

    98/103

    *

    *

  • 7/27/2019 Zia Seminar

    99/103

    * 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

    *

  • 7/27/2019 Zia Seminar

    100/103

    *

    * 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

    *

  • 7/27/2019 Zia Seminar

    101/103

    *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

    *

  • 7/27/2019 Zia Seminar

    102/103

    102

    * 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.

    *

  • 7/27/2019 Zia Seminar

    103/103

    *THERE IS A PRINCIPLEWHICH IS PROOF

    AGAINST ALL

    ARGUMENT, AND

    WHICH CANNOT FAIL

    TO KEEP MAN IN

    EVERLASTING

    IGNORANCE.