Zinc Oxide Eugenol Impression Paste

Composition:

Base Paste
- Zinc oxide 87%
- Fixed vegetable or mineral oil 13%
Accelerator Paste or Catalyst Paste:
- Oil of clove or eugenol (70 to 85%) – 12%
- Gum or polymerized rosin – 50%
- Filler (Silica type) – 20%
- Lanolin – 03%
- Resinous balsam – 10%
- Accelerator solution (CaCl₂) and coloring agents – 05%

Role of Each Ingredient

Zinc oxide: Main ingredient to react with the catalyst. It should be finally divided and should contain slight amount of water.
Fixed vegetable or mineral oil: Acts as a plasticizer and also aids in masking the action of eugenol as an irritant.
Oil of clove: It contains 70–85% eugenol. It reduces the burning sensation or irritant effect of eugenol.
Gum or polymerized rosin: Speeds the reaction and improves homogeneity.
Canada or Peru balsam: Improves flow and mixing properties.
Filler: It provides proper consistency of the mix.
Calcium chloride: Acts as an accelerator of setting reaction.
Other Accelerators:
- Zinc acetate
- Primary alcohol
- Glacial acetic acid.

Uses of Zinc Oxide Eugenol Impression Paste:

Properties of Zinc Oxide Eugenol Impression Paste:

Consistency and flow: A thin free flowing material copies the tissues without distorting them. Clinically these materials have very good flow. According to ADA specification No. 26, the spread is:
- Type I paste: 30 to 50 mm
- Type II paste: 20 to 45 mm.
Detail reproduction: It registers surface details quite accurately due to the good flow.
Rigidity and strength: The impression should resist fracture and be unyielding when removed from the mouth.
The compressive strength of hardened ZOE is 7 MPa two hours after mixing.
Biological consideration: Some patients may experience a burning sensation in the mouth due to eugenol. It can also cause tissue irritation.

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