Definition:
Zinc oxide–eugenol paste is a rigid, non-elastic impression material formed by mixing zinc oxide powder with eugenol liquid. This results in an irreversible reaction that produces a hard, brittle mass. It is primarily used for edentulous impressions where tissue displacement must be minimal.
Uses:
Final impressions for complete dentures
Situations requiring minimal tissue compression
Recording fine details of edentulous ridges
Not recommended in:
Patients with deep undercuts → risk of fracture on removal
Crown and bridge impressions → non-elastic so it cannot adapt to prepared teeth
How to use clinically:
Dispense powder and liquid according to manufacturer instructions.
Mix to a smooth, uniform consistency.
Apply a thin layer to the custom tray (wash technique) and additional bulk in stress-bearing areas if required.
Seat tray over tissues; maintain position without pressure.
Allow to set (5–7 minutes).
Remove carefully in one piece - try to avoid flexing the impression
Tips:
Avoid excessively thick layers → as this prolongs the setting time and may increase the risk of fractures
Use custom trays for better adaptation and support
Constituents:
Component | Amount (%) | Purpose |
|---|---|---|
Zinc oxide powder | 85-90 | Provides structure |
Eugenol liquid | 10-15 | Hardens the zinc oxide |
Fillers/ accelerators | Trace | Controls setting rate and consistency |
Gum or polymerised rosin speeds the reaction up
Canada balsam and peru balsam improves flow and mixing properties
Calcium chloride acts as an accelerator to the setting reaction. Other accelerators include zinc acetate, primary alcohols, glacial acetic acid.