Microbiological effects of new agents in dentifrices for plaque control

The incorporation of antimicrobial agents in dental products has been proposed for many years as a possible valuable adjunct to mechanical plaque control. Out of the diverse collection of potential agents, relatively few can be formulated into dentifrices. Several products have been developed based on Triclosan, a broad spectrum antimicrobial agent. By itself, Triclosan has only moderate antiplaque activities; consequently, it has been combined with other molecules in attempts to boost its clinical efficacy. The combination of Triclosan with a copolymer (polyvinyl methyl ether maleic acid) has been shown to increase the retention of Triclosan to surfaces, and to raise its antiplaque and antimicrobial activity in a range of laboratory tests. Other studies, however, have found greater inhibitory effects on both liquid and biofilm mixed cultures when Triclosan was combined with either pyrophosphate or zinc citrate. Both of these combinations were selectively inhibitory to those species implicated in gingivitis and advanced periodontal diseases. There is little microbiological data on the clinical efficacy of a combination of Triclosan with pyrophosphate, but as pyrophosphate has only a bacteriostatic mode of action and is lost rapidly from the mouth, this may limit the significance of any of its potential antimicrobial effects in vivo. In contrast, zinc citrate is a proven inhibitor of bacterial metabolism and growth, and is retained in the mouth for prolonged periods. Several clinical studies have confirmed an additive, complementary and selective inhibitory antimicrobial effect on dental plaque of a dentifrice containing Triclosan and zinc citrate, without any adverse effects on the natural microbial ecology of the mouth.