An in vitro mouth model to test antiplaque agents: preliminary studies using a toothpaste containing chlorhexidine.

The development of an in vitro model simulating the oral cavity has allowed the antiplaque activity of a toothpaste containing 0.004% chlorhexidine to be tested. The model is based on the continuous irrigation of bovine tooth samples with artificial saliva. Scanning electron microscopy showed homogeneous colonization of monobacterial plaque by Streptococcus mutans on dental surfaces under these model conditions. The enamel was colonized with regular cell clusters showing a globular appearance. The globules coalesced with increasing plaque thickness. Treatment with toothpaste containing 0.004% chlorhexidine showed a more marked inhibition of bacterial colonization on enamel surfaces than placebo paste lacking this antimicrobial agent. These results indicate that the toothpaste formulation is compatible with chlorhexidine. It is concluded that the in vitro model developed in this study is suitable for the testing of the antiplaque activity of antimicrobial agents, particularly when in a semisolid form such as in a toothpaste.