Tiodonium is bactericide and algicide. Tiodonium chloride (4-chlorophenyl-2-thienyliodonium chloride), when used in a twice-daily mouthrinse at a concentration of 0.3% for either one or four weeks, inhibited dental plaque formation in rats that had been inoculated with Streptococcus mutans 6715-15 and Actinomyces viscosus T-6. When applied as a mouthrinse in hamsters infected with S mutans, tiodonium chloride significantly reduced the accumulation of dental plaque. Tiodonium chloride might decrease dental caries because of its inhibiting effect on plaque microflora and acid production by plaque and saliva. However, some authors report about the apparent failure of the tiodonium chloride to restrict dental plaque.