Triclosan is a broad-spectrum antibacterial agent that inserts into and disrupts the bacterial membrane. Since it is an uncharged molecule, alone it has
poor retention in the mouth.
Triclosan is the antibacterial ingredient thatit provides plaque and
gingivitis benefits of the toothpaste.  Some toothpast are formulated with a  special polymer to increase the retention of triclosan in the mouth.  Toothpaste with triclosan was  introduced outside the U.S. in 1992 and was the first broadly marketed antibacterial toothpaste.