  An approximate model of the spacetime foam is offered in which each quantum
handle (wormhole) is a 5D wormhole-like solution. A spinor field is introduced
for an effective description of this foam. The topological handles of the
spacetime foam can be attached either to one space or connect two different
spaces. In the first case we have a wormhole with the quantum throat and such
object can demonstrate a model of preventing the formation the naked
singularity with relation $e > m$. In the second case the spacetime foam looks
as a dielectric with quantum handles as dipoles. It is supposed that
supergravity theories with a nonminimal interaction between spinor and
electromagnetic fields can be considered as an effective model approximately
describing the spacetime foam.
