B05    Justify the use of cavity varnishes, liners, and bases, and identify four required properties.

Varnish

Used to minimize microleakage and initial sensitivity for cold drinks. Makes it more difficult for corrosion products to diffuse into the dentin. The varnish is thin and should be placed on the cut enamel surfaces. Just make sure that the varnish does not pool adjacent to the margin.

Liners

Contain Ca(OH)₂. The calciumhydroxide stimulates reparative dentin formation. If a pulp horn was exposed, this region should be covered with a liner or a paste containing Ca(OH)₂.

Liners dissolve to some extent and should therefore not cover the cut enamel surfaces.

Bases

Key property is strength. They can therefore be used in rather thick layers. A thickness exceeding 0.75 mm is needed to achieve thermal insulation.

The base with the highest initial strength is zinc oxide eugenol, while the base with the highest strength after 24 h is the zinc phosphate cement. The advantages with both glass ionomer and polycarboxylate bases are that they bond to some extent to both enamel and dentin.

There are five properties that should be considered when varnishes, liners or bases are selected. These properties include:

1. Being as biocompatible as possible.
2. Being as inert as possible (except liners, which need to release Ca(OH₂)).
3. Being as thermally insolating as possible.
4. Being as strong as possible.
5. Being able to bond to tooth structures.