Though not taken in principles of cavity preparation it is one of the important steps before final restoration.

Pulpal injury can result due to:

  1. Heat generated by injudicious cutting.
  2. Restorative material with good thermal conductivity.
  3. Chemical from the restorative materials.
  4. Galvanic currents
  5. Microleakage.

Liners and bases are used fro pulp protection. Liners are volatile or aqueous suspensions or dispersion of zinc oxide or calcium hydroxide that can be applied to the cavity surface in a relatively thin film.

Bases are those cements, which are applied, in thicker dimensions beneath permanent restorations to provide for mechanical, chemical and thermal protection of the pulp.