Midterm

Question 1

• used for dentulous patients as they are elastic
• synthetic rubbers
• rubber impression materials
• ADA spec no. 19

Answer 1

Non-aqueous elastomers

Question 2

• liquid polymers converted to rubber at room temp by mixing with catalyst
• polyethers, polysulfide, silicones

Answer 2

non-aqueous elastomers

Question 3

• syringe consistency
• regular body
• tray consistency
• putty consistency

Answer 3

• light body
• medium
• heavy body
• very heavy body

Question 4

What are uses of non-aqueous elastomers?

Answer 4

• used as a final impression in fixed partial or removable partial denture
• impression of edentulous patients w/ undercuts and highly resorbed ridges.
• polyether can be used for border molding in final impression in complete denture construction
• bite registration materials
• duplicating material
• to record defects for oral and maxillofacial prosthesis

Question 5

non-aqueous elastomers

1. advantage
2. disadvantage

Answer 5

1. -good detail reproduction
   - good tear resistance
   - dimensionally stable
   - avail in different consistencies, so more accurate impressions can be made
2. -costly
   - isolation of the field to make impressions
   - poor wetting of die materials because of hydrophobic nature
   - stiff after setting, may cause discomfort to patient after removable
   - removable of cast may be difficult if material becomes stiff on setting

Question 6

• 1st elastomers used
• aka mercaptan or Thiokol
• 2 paste system:
• lithophone and titanium dioxide 16-18%:
• ZnSO4, CuCO3, ZnO, CaSO4 or silica

Answer 6

Polysulfide elastomeric impression material

*filler to provide the required strength, to produce viscosity and whiteness

Question 7

• usually white colored paste
• sodium polysulfide polymer
• converts to solid rubber by oxidation

Answer 7

Base paste Polysulfide elastomeric impression material

Question 8

• usually brown colored paste
• lead dioxide or peroxide
• copper oxysulfate 60-68%: oxidizing agent, acts as catalyst for polymerization, on curing gives dark brown color and unpleasant odor
• dibutyl or dioctylphthalate 30-35%: plasticizer to provide viscosity
• sulphur 3%: enhance reaction
• castor oil
• magnesium stearate or oleic acid 1-2% retarder
• deodorants provide pleasant smell

Answer 8

Accelerator paste

Question 9

butyl rubber or styrene acrylonitrile dissolved in volatile solvent such as a chloroform or ketone

Answer 9

Tray adhesive Poly sulfide elastomeric