This study will explore some of the mechanisms of fluoride inhibition of microbial growth and metabolism. Bacteriocidal/bacteriostatic activity and metabolic abberations induced by various concentrations of NaF will be evaluated in cultures of fluoride-sensitive and fluoride-resistant strains of Strep. mutans, and in washed cells suspended in a buffered glucose solution. The survival of fluoride-treated organisms will be assessed by the quantitative recovery of colony-forming units. Metabolic alterations will be determined by gas liquid chromatographic (GLC) analyses of the sugar, alcohol, and acid partitions in cells and spent media. Identical procedures will be used to assess fluoride - induced changes in human dental plaque.