Zinc Oxide Eugenol(ZOE) cements are noted for the sedative effect eugenol has on the pulp of teeth. Eugenol is found in the oil of cloves. The two component Zinc Oxide Eugenol cements are available in either paste/paste or powder/liquid formulas. Zinc Oxide Eugenol cements are commonly used as cavity liners under dental amalgams or as temporary filling material in cases where severe pulpal irritation has occurred. A minimum thickness of 0.5 mm ZOE is required to protect the pulp.
When used as a temporary filling material, Zinc Oxide Eugenol can remain in the cavity for a few days, which is long enough for the sedative effects for vital tissues of the tooth. It should then be removed for the placement of the permanent restoration. Reinforced resin containing ZOE can be used as a temporary filling material for as long as six months.
Use of Zinc Oxide Eugenol as Base, Liner, and Filling Material
Zinc Oxide Eugenol cement is prepared for use by mixing thoroughly on mixing pad the zinc oxide powder and eugenol liquid, with the help of a small spatula. The amount of eugenol depends on the amount needed. For a base material, the mixture should be of medium to heavy consistency (like putty). For temporary fillings, the material is mixed to a very heavy consistency. As the proper thickness is achieved, zinc acetate crystals can be added to accelerate the material’s hardening.
When the Zinc Oxide Eugenol is used as a base, the operator carries it to the cavity preparation with a ball-tipped applicator or plastic filling instrument. When the ZOE is used as a temporary filling, the operator carries it to the tooth with a plastic filling instrument and packs it into the prepared cavity. When using the Zinc Oxide Eugenol product called IRM (Intermediate Restorative Material) for temporary fillings, mix the two components (powder and liquid) to a very heavy consistency. Operator places the material in the tooth, and then packs it into the cavity preparation with a placement instrument.
Use of Zinc Oxide Eugenol as Luting Cement
ZOE is the most commonly used cement for temporary cementation of crowns and bridges. Eugenol’s sedative effect is especially applicable to just-completed crown preparations, reducing postoperative sensitivity. Zinc Oxide Eugenol cement properties are improved through the addition of orthoethoxybenzoic acid and quartz or alumina fillers. These cements can also be used for permanent cementations.
Technique for Zinc Oxide Eugenol luting cements:
Prepare the mixture using the following procedure:
1. Place equal amounts of the two components (base and catalyst) on a medium-size, polycoated mixing pad.
2. Spatulate (mix with a spatula) the two components to a homogeneous mix, being careful not to incorporate air bubbles.
3. Make sure that the crown/bridge and the tooth are dry. Use the air syringe to blow- dry any moisture.
4. Using the spatula, a spoon excavator, or ball applicator, transfer the cement to the inner surfaces of the crown or bridge. Be sure that all inner surfaces are coated and no air bubbles are present.
5. If there are any air bubbles, place the end of the spatula into the cement in the crown and press until the air is released.
6. Place the crown or bridge onto the tooth’ teeth and push firmly into place.
7. While the cement sets, maintain pressure on the crown/bridge by having the patient gently close his or her mouth, biting on a cotton roll or bite stick.
8. Once the material is set, remove excess cement from the margins with an explorer, excavator, or scaler.
Hints: There are several things to keep in mind when working with Zinc Oxide Eugenol cements.
• Any leftover powder of any cement should not be put back into its container. Throw it away!
• Too much cement in the crown before placement will prevent proper seating.
• Cements achieve their highest strengths when their film thicknesses are consistent and minimized.
• Zinc Oxide Eugenol cements should not be used with acrylic temporaries that will be in place for long periods of time.