Elastomeric Impression Materials

Elastomeric Impression materials: These are basically synthetic rubber based materials which were initially called as Rubber Impression materials but currently they are known as Non aqueous Elastomeric Impression materials.

Classification of Elastomeric Impression materials:
Till now the elastomeric impression materials are divided into 3 types based on the material used

1. Polyether
2. Polysulfide
3. Silicone

• Addition
• Condensation

POLYETHER IMPRESION MATERIAL

• Introduced in Germany in late 1960’s
• 1^st Elastomers to be developed as impression material.

Composition:

Base Paste:

1. imine terminated polymer(polyether)
2. colloidal silica
3. glycol ether or phthalate

Accelerator Paste:

1. alkyl aromatic sulfonate
2. colloidal silica
3. plasticizers ( glycoether )

Setting Reaction:

polyether + sulfonic ester –> cross linked rubber.

Properties:

1. setting time:  8.3 min.
2. mixing time – 30 sec.
3. dimensional stability is good.
4. decreased flexibility – 3%
5. hydrophilic
6. activator paste can produce allergy if handled frequently.
7. tear strength – 3000gm/cm
8. shelf life > 2 yrs.

Advantages:

1. short working & setting time
2. proven accuracy
3. adequate tear strength
4. hydrophilic
5. long shelf life
6. less distortion on removal
7. good dimensional stability.

Disadvantages:

1. stiffness requires blocking of undercuts
2. slightly more expensive
3. multiple casts can’t be poured due to stiffness of the material.

Manipulation of Elastomers:

Manipulation of two paste systems

• equal length of base & activator paste are taken.
• Paper pad with graduations is provided by manufacturer.
• Pastes are mixed till no streaks are present.
• Tray coated with tray adhesive. Uniform two-layer coat is applied & allowed to dry.
• The mixed material can either be taken in a syringe or loaded directly in the tray.

Manipulation of Putty Material:

• Putty dispenser is supplied with scoops for dispensing.
• Activator may be a liquid or paste.
• Putty material is taken in a scoop & the activator is added. Usually the activator is of different color.
• It is kneaded till no streaks are present.
• Putty material is used with stock trays.