Which acid etchant is used for glass ionomer restorations and for what length of time?

The correct choice involves the use of polyacrylic acid as an etchant for glass ionomer restorations, with an etching time of 15-30 seconds. Polyacrylic acid is specifically used for glass ionomer cement because it is less aggressive compared to phosphoric acid, making it suitable for this material. Glass ionomers are sensitive to over-etching, which can compromise their bonding properties and strength, hence the shorter etching duration.

Using polyacrylic acid allows for effective conditioning of the glass ionomer surface while maintaining its integrity. This procedure is crucial for achieving a proper bond and achieving the material's intended performance in clinical situations. The specific timing of 15-30 seconds ensures that the etching process enhances the bonding without risking damage to the material's structure.