ELASTOMERIC IMPRESSION MATERIALS -POLYSULPHIDE AND CONDENSATION SILICONE

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 ELASTOMERIC IMPRESSION MATERIALS

 - PART 1 

  • ELASTOMERIC :Rubber -like polymers that shows as elastic behaviour at the time of load application 

  • These polymer molecules have weak interaction in between (Van der wall forces)

  • They have tied together in 3D network 
4 ELASTOMERIC IMPRESSION MATERIALS:

1)POLYSULFIDE

2)CONDENSATION -POLYMERIZATION SILICONE

3)ADDITION-POLYMERISATION SILICONE

4)POLYETHER  

1)POLYSULPHIDE:
  • 1st material introduced also known as mercaptan/thiokal
Collapsible tubes :
  • Base: White colour
  • Catalyst: Brown,grey 
VISCOSITIES:
  1. Heavy
  2. Medium
  3. Putty
BASE :
  • Low molecular weight polysulphide
  • Filler (Titanium dioxide)
  • plasticizer(Dibutyl phthalate)
  • Accelerator(0.5% Sulphuric acid )
CATALYST:
  • Lead oxide
  • Filler (Titanium dioxide)
  • Plasticizer(Dibutyl phthalate)
  • Retarder(Oleic acid and Stearic acid)
Condensation polymerisation:
  • Mercaptan+lead dioxide  = polysulphide +water
CHARACTER:
  1. Water by product +polymerisation shrinkage =dimensional changes
  2. Water could cause air bubble in stone cast
  3. Hydrophobic,can be electroplated
ADVANTAGE:
  1. Modest cost
  2. Easily seen margin
  3. High tear resistance
  4. Long working time 
DISADVANTAGE:
  1. Require custom tray
  2. Stain clothing
  3. Pour within 1 hour 
2)CONDENSATION SILICONE :

Available in 3 viscosities:
  1. Putty
  2. Medium
  3. Light
PASTE:
  • 2 unequal size collapsible tube 
  • Base:Large ,Catalyst -Small
  • Putty :Jar,Catalyst :1)Liquid, 2)Paste 
BASE:
  • Polydimethylsiloxane (Hydroxy terminals)
  • Filler 
  • Colour pigment 
CATALYST:
  • Ortho Ethyl silicate 
  • Stannous octoate
  • Dimethyl siloxane +Silicate =Silicone +Ethyl alcohol
CHARACTER:
  • Condensation polymerisation 
  • Ethyl alcohol +polymerisation shrinkage =dimensional change
  • Alcohol air bubble
  • Hydrophobic ,electroplate
ADVANTAGE:
  1. Clean,pleasant 
  2. Good working time 
  3. Easily seen margin
DISADVANTAGE:
  1. Pour immediately
  2. Low tear strength
  3. Hydrophobic 
AIM OF THIS POST :

Today we started with a small introduction on what an elastomeric impression material is then we moved on to the classification of elastomeric impression and finally we discussed in detail about polysulphide and condensation silicone material ,The next post will be highlighting on addition and condensation silicone .If this post helped you learn then do let me know in the comment section below as this would motivate me to post more such content .







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