What is the defining property of a liner in dental preparation?

The defining property of a liner in dental preparation is that it is applied over dentin for protection. Liners serve a critical role in dental procedures, as they are used to cover exposed dentin, providing a barrier against thermal, chemical, and bacterial stimuli that could irritate the pulp tissue underneath. This protective application helps to maintain the health of the tooth structure and prevent pain or sensitivity.

In contrast to liners, bases are typically thicker materials that offer additional strength and thermal insulation, which is essential in deep cavity preparations where a significant portion of the dentin is removed. Unlike liners, bases are designed to also support restorative materials due to their bulk and strength. Liners are not limited to being placed only on the occlusal surfaces, as they can be utilized on any area where dentin exposure occurs. Furthermore, liners are not utilized for filling large cavities; rather, they may be used in conjunction with other restorative materials to assist in managing pulp sensitivity without taking the place of the main restorative filling.