Zinc Oxide Eugenol Impression Paste
- The ZOE impression paste is a rigid, irreversible material.
- It is mainly used for making an impression of an edentulous mouth.
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:
- As cementing and insulating medium
- As temporary filling material
- As root canal filling material
- As surgical pack in periodontal surgeries
- For bite registration
- As temporary relining material for dentures
- For taking an impression in edentulous patients.
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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