You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Cavity varnishes have: and explain in detail?
Cavity varnish is a solution of one or more resins which when applied onto the cavity walls, evaporates leaving a thin resin film, that serves as a barrier between the restoration and the dentinal tubules.
Varnishes neither possess mechanical strength nor provide thermal insulation because of the thin film thickness. The film thickness ranges from 2 to 400 µm. The solubility of dental varnishes is low; they are virtually insoluble in water.

Ref- Manapallil 3rd Ed P:81