Dental cavity liners are designed to provide a base beneath both direct and indirect restorations that seals the underlying tooth structure and protects it from bacteria and possible irritants. Liners are applied in thin layers and can be a wide range of materials including glass ionomers, resins, and more. Some resins provide release of fluoride and other beneficial compounds. As with all dental materials, it is important to use a cavity liner as directed and to ensure it is compatible with the case being treated and the other restorative materials being used.