Protective effect of polystyrene liners for composite resin restorations

The main purpose of lining cavities before insertion of composite resin restorations is to prevent bacterial contamination at the cavity walls. A thin film of polystyrene liner dissolved in ethyl acetate applied to all surfaces by compressed air provided good protection against bacteria on cavity walls under composite resin restorations. An antibacterial primer in an alcohol solution applied prior to the liner may improve this protection. This procedure had no detectable injurious effect on the pulp.