B06    Identify the basic difference between a varnish and a base, as well as two shortcomings of these two materials.

A varnish is a thin film with rather low solubility in water. A varnish does not contribute with strength nor thermal insulation. A varnish can cover all cavity surfaces.

Bases are often slightly pulp irritating since they consist of a powder mixed with an acid. Bases are strong and can contribute with some thermal protection if their thicknesses exceed 0.75 mm. Bases dissolve to some extent in oral fluids and should therefore not cover more than the exposed dentin surfaces.

A varnish (or a liner) should be used under a zinc phosphate base if the base is close to the pulp.