Zinc Phosphate Cement – Eugenol has an adverse reaction on acrylic materials and should not be used with acrylic temporary crowns that will be in place for long periods of time. Eugenol vapours attack the acrylic polymer, softening the acrylic and crazing its surfaces.
Because of this, zinc oxide noneugenol cements are generally used in place of ZOE temporary luting cements. This is available as a two-component paste/paste formulations.
Zinc Phosphate Cement exhibits an exothermic (heat-producing) action as the powder and liquid are mixed, so it is always mixed on a cool glass slab, never on a paper pad. The maximum mixing time is 90 seconds with a setting time of 5—7 minutes in the mouth.
For any product, follow the manufacturer’s directions for powder/liquid dispensing ratios. To mix this cement following steps are followed:
1. Place the powder on the glass slab and divide it into small increments.
2. After placing the liquid, bring small amounts of powder into the liquid with the help of spatula, and spatulate thoroughly (about 10— 15 seconds) after each addition.
3. To help dissipate the heat, use a large area of the glass slab when mixing the cement.
Zinc Phosphate Cement
Zinc phosphates is the first permanent cement for crowns and bridges. These powder/liquid cements are based on a zinc oxide and magnesium oxide powder and phosphoric acid liquid. Zinc Phosphate Cement has excellent strength (approx. 9,000 psi). It is used primarily as permanent luting cement and occasionally as a base placed over calcium hydroxide.
If you need to prepare the Zinc Phosphate Cement for a base, mix it in two or three increments and use more powder to make a heavier mixture. This will set faster and must be used immediately.