Ionosit Microspand is a base material for composite and amalgam restorations that can be used to block out undercuts in inlay or onlay restorations. It is a patented, single component, light-cured base material that expands to compensate for polymerization contraction. The advanced chemistry of Ionosit MicroSpand forms a "sensitivity shield" that effectively eliminates micro-leakage and recurrent caries, and guards against discomfort and pain.