This document discusses the properties and uses of polysulfide impression materials. Polysulfide impressions materials are liquid polymers that harden at room temperature when mixed with a catalyst. They consist of long polymer chains that are cross-linked. When the base and accelerator pastes are mixed, a chemical reaction occurs due to oxidation that causes the material to set within 5-8 minutes. Polysulfide impressions are dimensionally stable and accurate, with high tear strength, and are commonly used for final impressions in dentistry.

1.  Chemistry.
 They are liquid polymers converted to rubber
at room temperature by mixing with a
suitable catalyst.
 They consist of large molecules or polymers
that are joined by cross linking.
 The first synthetic rubber like material was
produced by a process known as ‘
vulcanization’ or curing.

2. Based on chemical composition:
 1. Polyether.
 2. Poly sulfides.
 3. Silicones :
 Addition
 Condensation.
Based On Viscosity:
 1. light body or syringe consistency.
 2. Medium or regular body.
 3. Heavy body/ Putty

3.  Final impression in fixed partial denture
and removable partial denture
construction.
 Impression of edentulous ridge with
undercuts or highly resorbed ridges.
 For border moulding in CD.
 Bite registration material.
 Duplicating material.
 Record defects for oral and maxillofacial
prosthesis(obturators).

4.  Available as:
 Light bodied
 Medium bodied
 Heavy bodied

6. Base paste:
 White coloured
 Sodium polysulfide polymer(co-polymer of
ethylene chloride,Thiokol polysulfide,
dimercapton polysulfide) 80-85% :
Convert to solid rubber by oxidation.
 Lithophone and titanium dioxide 16-18% :
Provide strength, viscosity and
whiteness.
 znso4 ,cuco3 ,zno, caso4 or silica

7. Accelerator paste:
 Brown colored paste.
 Copper oxysulfate (alternate to lead dioxide) 60-68%:
Oxidising agent act as catalyst
 Dibutyl or Dioctylphthalate 30-35%:
plasticizer
 Sulfur 0.5-3%: to enhance reaction
 Castor oil 5-8%

8.  Other substances such as magnesium
stearate or oleic acid (retarder) 1-2%:to
control setting time
 Deodorants (traces) pleasant smell.
Tray adhesive:
 Butyl rubber or styrene acrylonitrile
dissolved in a volatile solvant such as
chloroform or ketone.

9.  Mercaptan + lead dioxide =polysulfide
+water
 Chain lengthening by oxidation of terminal –
SH group
 Cross linking by oxidation of the pendant-SH
group
 Exothermic reaction with rise of 3 – 4 degree
C in temp.
 Heat and moisture accalerate the reaction.

10.  Setting time 5-8 min.
 Colder time increase setting time
 Drop of water accalerate reaction
 Excellent detail reproduction
 Dimensionallt stability
 Curing shrinkage 0.45%
 Shrinkage due to loss of byproduct

11.  Permanent deformation 3-5 % (highest in
elastomers)
 High tear strength 7000gm/cm2
 Good flexibility 7%
 Hydrophobic
 Can be electroplated with copper
 Toxic effects due to lead content

12.  Long working time
 Proven accuracy
 High tear resistance
 Inexpensive to use
 Less hydrophobic
 Longer shelf life

13.  Must be poured with dental stone
immediately
 Potential for significant distortion
 Odor is offensive
 Messy and stains cloths
 Second pour is less accurate.

15.  With putty
 With putty and lighter body material
 With flow-able material loaded in tray and
syringe

20.  2 Syringe cartridges with gun – base and
accelerator supplied as Light, Medium or
Heavy body