Polysulfide elastomeric impression material Flashcards
1
Q
aka
A
mercaptan or thiokol
2
Q
viscosities
A
light, medium, heavy
3
Q
what is the base paste?
and consists of?
A
- usually white colored paste
- Sodium polysulfide polymer
- lithophone and titanium oxide 16-18%
- ZnSO4, CuCO3, ZnO, CaSO4 or silica
4
Q
what is Sodium polysulfide polymer?
A
- copolymer of ethylene chloride, Thiokol polysulfide, dimercapton polysulfide 80-85%
- converts solid to rubber by oxidation
5
Q
what is lithophone and titanium oxide 16-18%
A
-filler to provide the required strength, to produce viscosity and whiteness
6
Q
What consists the accelerator paste?
A
- brown paste
- lead dioxide or peroxide
- copper oxysulfate(60-68% oxidizing agent, catalyst for polymerization giving brown color)
- dibutyl or dioctyphthalate(30-35% plasticizer to provide viscosity)
- sulphur (3%)
- castor oil
- magnesium stearate or oleic acid (1-2% retarder)
- deodorants
7
Q
tray adhesive
A
butyl rubber or styrene acrylonitrile dissolved in volatile solvent such as chloroform or ketone
8
Q
setting reaction
A
- mercaptan + lead dioxide -> polysulfide + H2O
- chain lengthening & cross-linking by oxidation of SH groups
- exothermic 3-4 deg rise in temp
- setting time 5-8 min, cold or water accelerates rxn
9
Q
dimensional stability
A
-curing shrinkage (0.45% due to continued rxn due to loss of by product (H2O)
10
Q
permanent deformation 3-5%
A
highest among elastomers, produced by rocking the impressional while removal
-should be removed with a single swift pull to allow elastic recovery.
11
Q
other features
A
- high tear strength
- good flexibility
- hydrophobic
- electroplated with copper
12
Q
advantages
A
- long working time
- proven accuracy
- high tear resistance
- inexpensive to use
- less hydrophobic
- longer shelf life
13
Q
disadvantages
A
- must be poured w/ dental stone immediately
- potential for significant distortion
- odorous
- messy and stains clothes
- second pour is less accurate
