ZOE (Zinc Oxide Eugenol) Impression Material Handling Guide

Classification: ZOE belongs to non-elastomeric impression materials group.

Composition: It is available as two pastes. One paste, called the base contains zinc oxide (ZnO), oil, and hydrogenated rosin. The second paste, the accelerator, contains about 12% to 22% eugenol, oils, rosin, and a filler such as talc or Kaolin. These two pastes have contrasting colors so it can be determined when the pastes are thoroughly mixed. We will be using Bosworth Superpaste ZOE impression material in the Main Clinic for only selected prosthodontic cases. Please see below indications part for proper selection of the cases.

Advantages:

– Cost effective
– Does NOT cause displacement of tissues, second best to impression plaster for making mucostatic impression
– Does NOT need uniform thickness, will work with little space
– Provides detailed production of the soft tissues due to its low viscosity
– Dimensionally stable. A negligible shrinkage (less than 0.1%) may occur during hardening

– No need for tray adhesive. It adheres well to impression compound

Disadvantages:

– Messy to work with. Sticks to skin and instruments, difficult to clean. – It might cause burning sensation due to eugenol content
– Unpleasant taste
– Rigid and brittle once set thus unable to record undercuts

– Setting time varies with temperature and humidity

– Can only be poured once

Indications:

–  Final impression of atrophied edentulous ridges with a close-fitting tray

–  It can be used as a wash impression over the impression compound in a custom acrylic tray (e.g. for altered cast impression of partially edentulous mandibular arch when there is no undercut). For this purpose, green stick compound is heated and applied to the intaglio surface of the denture base, tempered in a water bath and seated in the patient’s mouth. This sequence must be repeated until an accurate impression of the edentulous ridge has been accomplished. The border extensions are determined by heating to the borders and carrying out border moulding procedure

–  It can also be used as a bite registration material

Contraindications:

– Should NOT be used with patients allergic or sensitive to eugenol
– Should NOT be used on edentulous ridges with undercuts. It will fracture if undercuts are present
– Should NOT be used if the impression cannot be poured within 7 hours3 after impression was taken

Instructions for use:

1. Extrude equal volumes of Superpaste catalyst (green) and base (white) on paper mixing pad. Variation in length alters setting time
2. Mix material quickly to uniform color with a stiff stainless-steel spatula (Alginate mixing spatula could be used.) Approximately 30 seconds to 1 minute
3. Apply mix to tray evenly. Load time is approximately 30 to 60 seconds. No need to apply tray adhesive
4. Insert tray and position slowly without pressure. It sets approximately in 3 minutes. Setting time is affected by temperature and humidity. Warmer temperatures and higher humidity accelerate set andcolder temperatures and lower humidity delay set. Use only at room temperature
5. Remove from mouth, rinse with cold water to remove saliva and disinfect the impression. For disinfection of the impression, immerse it in freshly prepared 1% sodium hypochlorite solution for 10 minutes and rinse it thoroughly afterwards. Pour up the model within 7 hours after the impressionwas taken to get the best result

Fabrication of close-fitting tray: As the name suggests, it is adapted directly on to the cast without any wax spacer. For border molding procedure, the tray border should be 2mm short of the true vestibule to leave room for green stick compound. Tray handle needs to be prepared in the same way we do for our custom trays. Pressure relief holes need to be drilled prior to impression taking. No need to apply tray adhesive.