The glucan-binding lectins of Streptococcus cricetus AHT and Streptoco
ccus sobrinus 6715 were reversibly inhibited by sodium fluoride. Fluor
ide was superior to chloride, bromide, iodide and thiocyanate in preve
nting glucan-mediated aggregation of the bacteria. Fluoride was also a
n effective inhibitor of the sucrose-dependent adhesion of S. sobrinus
to glass surfaces. The inhibition of glucan-binding lectin activities
may be one of the mechanisms of action of fluoride in preventing dent
al disease.