Contemporary strategies and materials to protect the dental pulp

When returning damaged teeth to form and function, the aim of restorative dentistry must also be to preserve the heath and integrity of the dental pulp. The disease process and subsequent operative intervention will cause an inflammatory response within the pulpal tissues. It is important that the restorative dentist considers the measures that he or she can take to protect this inflamed tissue and create an environment which is conducive to healing. Traditionally, linings and bases were placed on the pulpal surfaces of cavities in an attempt to achieve this aim. However, knowledge and understanding have advanced and, with the development and availability of new dental materials, new strategies are employed in contemporary practice. This paper reviews the approach employed for many years after cavity preparation and explores how this new thinking, combined with newer dental materials, has shaped the current management of pulpal protection.

For many years, once cavity preparation had been completed, an intermediate material¹ was placed on those surfaces overlaying the pulp prior to the placement of the definitive facilitating material. The selection of this restorative material was influenced by the proximity of the pulp following caries removal.¹ These materials were crudely classified into liners or bases. Baum et al's Textbook of Operative Dentistry,¹ whose ninth edition was published in 1985, defined liners as ‘materials that are placed as thin coatings, and their main function is to provide a barrier against chemical irritation. They do not function as thermal insulators. They are not used to produce a structural form for the preparation. Examples of liner materials are varnish-type materials to which calcium hydroxide or zinc oxide powder is added.’¹ Bases, on the other hand, ‘function as barriers against chemical irritation, provide thermal insulation and resist forces applied during condensation of the restorative material. They are capable of being shaped and contoured to specific preparation forms. Examples of these materials are zinc oxide-eugenol, zinc phosphate, zinc polycarboxylate (polyalkenoate/polyacrylate), and glass ionomer cements and some of the commercial preparations containing calcium hydroxide.’¹ Furthermore, bases were effectively a dentine replacement material used to decrease the bulk of restorative material.² Depending on the depth of the cavity, these materials were used singly or in combination with another.