What is the purpose of using a liner in a cavity preparation?

Using a liner in cavity preparation primarily serves the purpose of providing insulation from thermal stimuli. This is essential because after a cavity has been prepared, the remaining dentin can be quite vulnerable to thermal changes, which can cause discomfort or sensitivity for the patient. The liner acts as a barrier, helping to protect the pulp from temperatures (heat or cold) that could result from the restorative materials or from external stimuli.

The liner may also offer some degree of chemical protection and support to the dentin. While the other options relate to different aspects of dental materials and procedures, they do not accurately reflect the main purpose of using a liner. Etching enamel surfaces is a process often associated with bonding and does not involve the use of liners, whereas increasing bond strength is more related to adhesives and bonding agents. Color stability is relevant to the aesthetics of dental materials but does not pertain to the function of liners in cavity preparations.