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    ELASTOMERIC IMPRESSION

    MATERIALS

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    Elastomeric Impression

    Materials

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    ADA specifcation number 19

    Non aqueous elastomeric dental impression

    material. Liquid polymers which can convert to solid

    rubber at room temperature , by mixin a suitable catalyst

    !ubber base or rubber impression material "lastomers or elastomeric impression material

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    Elastomeric =

     Rubber-like polymers tat so! an elastic bea"ior at te time o# loa$

    application

     #hese polymer molecules

    have wea$ interaction in

    between (Van der Wall forces), althouh they are tied toether in 3D networ$.

    %n stretchin (on loading) chains uncoil

    At rest (o loading) chains snap bac$   C

          e  m

       i  c   a

       l   N

      a    t  u   r  e

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    %i&er tear stren&t

    More stable $imensionally in stora&e

    (No Synersis, Imbibation or Evaporation)

    Ability to be electroplate$

    'ut( )uite E*pensi"e ++++n co

    m p a r so

    n

    o

          y   $

      r   o   c   o    l   l  o   i

       $   s

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        t  y   p   e  s

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    #

      o   r   m   s

    Materials’ Consistency

    Light

    Medium

    Heavy

    Putty Silicone materials only

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    &eneral 'eatures o' elastomeric

    impressions "xcellent reproduction o' details

    (ydrophobic

     &ood elastic recovery

    Dimensionally stable

    &ood tear strenth

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    )ses *mpression in fxed partial denture cases

    *mpression o' dentulous and edentulous

    arches +ite reistration

    +order moldin o' special trays

    Duplicatin material.

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    Polysul.$e Rubber Impression Material

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    C%EMISTR/

    A0 Composition1

      Base paste 1. LMW Polysulfide with two terminal and one pendant

    SH groups

    2. Fillers (Titanium dioxide) 3. Plasticizer (Dibutyl phethalate)

      Catalyst paste

    1. Lead dioxide (rown) or   organic peroxides (!ray) reactor  2. Fillers (Titanium dioxide) 3. Plasticizer (Dibutyl phethalate)

     

       R   u

       b    b  e

      r

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       R   u

       b    b  e

      r

    B. Setting eaction!

    Condensation poly"erization (exothermi" # shrin$age) #it$

    releasing of %2& as reaction

    'y(product

     )t occurs as a series of si"ple oxidation reactions

     &xidation of  ter"inal S%

    groups  poly"er c$ains

     &xidation of  pendent S%

    groups  Cross(lin*ing

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     Material sets +ia condensation poly"erization

    reaction

     Water is t$e reaction 'y(product  ,+aporation of #ater - poly"erization s$rin*age 

    i"ensional c$anges in storage

     Water could cause air 'u''les in stone cast

     Polysulfide is $ydrop$o'ic/ and can 'e electroplated

     Lead dioxide is toxic and $as 'ad s"ell/ so it

    $as 'een replaced in recent products 'y

    peroxide co"pounds

     

       R   u

       b    b  e

      r

     O'2IO3S C%ARACTERS

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    Con$ensation Silicone

    Impression Material

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    C%EMISTR/

    A0 Composition1

      Base paste

    1. LMW silicone poly"er with terminal OH groups2. Fillers (%olloidal sili"a or titanium dioxide) (white)

      Catalyst paste 1. 0l*yl silicate (%ross lin$ing)

    2. in dilaurate or Stannous octoate (&"tivator)

     

       S    i   l    i  c   o  n

      e

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    B. Setting eaction!

     Condensation poly("erization (exothermi" # shrin$age) 

    releasing C2%&% as reaction 'y(product

     )t occurs as a series of cross(lin*age of siloxane poly"er  

    to al*yl silicate in presence of t$e acti+ator/ to for" a 3D 

    poly"er net#or*

     

       S    i   l    i  c   o  n

      e

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    Material sets +ia condensation poly"erization

    reaction

    ,t$yl alco$ol is t$e reaction 'y(product  ,+aporation of alco$ol -  poly"erization s$rin*age  

    i"ensional c$anges in storage  t$at of polysulfide  0lco$ol could cause air 'u''les in stone cast

     Cond. silicone is $ydrop$o'ic/ and can 'e electroplated

    eit$er #it$ sil+er or copper 

     

       S    i   l    i  c   o  n

      e

     O'2IO3S C%ARACTERS

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    A$$ition Silicones Impression Materials

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       A    $    $    i   t    i  o   n

       S   i   l    i  c   o   n   e  s

     C%EMISTR/

    A0 Composition1

      Base paste 1. Poly "et$yl $ydrogen siloxane (Hydried or silane

    terminated sili"one)

    2. &t$er Siloxane pre(poly"ers

    3. Fillers

     Catalyst paste1. i+inyl poly4di"et$yl siloxane5 2. Platinu" salt acti+ator (%hloroplatini" a"id)

    3. Siloxane pre(poly"ers

    6. Fillers

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    B. Setting eaction!

     0ddition poly"erization (exothermi" # shrin$age) #it$ no

    release of 'y(product

     )t occurs as a series of cross(lin*age 'et#een +inyl(

    ter"inated silicon  and silane(ter"inated (hydried) silicon

    "olecules/ in presence of t$e catalyst ( platinum salt ) to

    for" a 3D poly"er net#or*

     0 side reaction (Releasing hydrogen gas   Air bubbles in gypsum cast) "ay occur if !

    1. No balance between vinyl siloxane and the hydried silicone

    2. Moisture react with hydrides o the base polymer 

     0dding no'le "etal (platinum or palladium)  to t$e co"position #ill act as $ydrogen a'sor'er 

       A    $    $    i   t    i  o   n

       S   i   l    i  c   o   n   e  s

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    0dding surfactants (sur'a"e tension redu"ingagents) to t$e co"position of add. silicone $elp turns t$e "aterial to 'e $ydrop$ilic (water lover)

     0d+antages!

    1. !etter wetting o sot tissue registration o better details

    2. ↓ Air bubbles in gypsum cast

     isad+antages! 1. "iicult to be electroplated

    2. #etting reaction could be retarded in presence o sulur (in latex gloves)  or   sulate compounds (in gingival retra"tion "ords)

     %/4ROP%ILIC SILICONE

       A    $    $    i   t    i  o   n

       S   i   l    i  c   o   n   e  s

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    Material sets +ia 0ddition poly"erization reaction (No byprodu"t)    More di"ensionally sta'le t$an condensation(poly"erized "aterials

     %ydrogen gas "ay release fro" a side reaction inpresence of "oisture or i"'alance of t$e reactants. But, adding noble metal to the "omposition prevents the release o' hydrogen gas  no air bubbles in the gypsum "ast 

     0dd.silicone is $ydrop$o'ic and can 'e electroplated/ $o#e+er adding of surfactants turns t$e "aterial $ydrop$ilic

       A    $    $    i   t    i  o   n

       S   i   l    i  c   o   n   e  s

     O'2IO3S C%ARACTERS

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    Polyeter Rubber Impression Material

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     C%EMISTR/

    A0 Composition1

      Base paste 1. LMW polyet$er with terminal imine groups 

    2. Filler ("olloidal sili"a) 2. Plasticizer (dibutyl phethalate or gly"oether)

      C