The bulk of dental plaque is composed of bacterial-derived
extracellular polysaccharide known as glucan, which is
synthesized by streptococcal glucosyltransferase (Gtf) enzymes.
At least three Gtf gene products of
Streptococcus mutans
have been identified. GtfB synthesizes a polymer of insoluble
alpha1,3-linked glucan, GtfC produces a mixture of insoluble
alpha1,3-linked glucan and soluble alpha1,6-linked glucan, and
GtfD synthesizes an alpha1,6-linked soluble glucan.
Polysaccharides are important in the development of plaque and
in the pathogenesis of dental caries, so we therefore decided to
explore the effects of putative antiplaque agents on the
activities of streptococcal Gtf enzymes in solution and on the
surface of parotid-saliva-coated hydroxyapatite (SHA) beads. Most
of the agents tested, particularly cetylpyridinium chloride,
hexylresorcinol, alexidine dihydrochloride and triclosan,
inhibited the activity of GtfB in solution and on the surface of
SHA beads. The agents moderately reduced the glucan-forming
activity of GtfD in solution and on the surface of SHA beads, and
had no effect on the activity of GtfC in solution or on the SHA
surfaces. Several commercial mouthrinses were also evaluated for
their effects on reducing Gtf activity; only Plax(R) (European
formulation) significantly reduced Gtf activity, and its effect
was limited to GtfB in solution. These data suggest that some
mouthrinses are highly inhibitory towards GtfB enzymes only, and
are with low effect on GtfC and GtfD. This lack of effect may in
part explain the comparative poor clinical efficacy of some
antiplaque agents.
