The contractor will establish an in vitro plaque forming system to test a variety of agents for their potential to: prevent plaque formation; prevent plaque growth; and/or remove plaque. He will also determine the lowest effective concentrations of agents found active in the aforementioned tests. Five organisms, which are known to form plaque in vitro, are to be used in the test system, including Acetinomyces naeslundii, A. israleii, and A. viscosus as well as two chosen by the contractor.