In accordance with certain of its aspects this invention relates to an oral composition comprising an oral vehicle, a cationic or long chain tertiary amine antibacterial antiplaque agent and a water soluble diphosphono pyrrolidone compound of the formula: ##STR3## wherein the R"s are independently H, C1-6 alkyl or C2-6 hydroxyalkyl and X is an orally acceptable cation such as H, alkali metal (e.g.