For supporting complex amalgam restoration, which of the following cement has best modulus of elasticity?
ZOE
GIC
Polycarboxylate
Zinc phosphate
Zinc phosphate cement has compressive strength of 104 MPa and modulus of elasticity of 13 GPa.

In very deep cavities with microscopic exposure, it is recommended that calcium hydroxide should be applied followed by zinc oxide eugenol or zinc phosphate under the restoration. 
For amalgam restorations, zinc phosphate is recommended as cavity base.