Dental plaque contains oral bacteria that metabolise dietary fermentable carbohydrates to produce short-chain carboxylic acids such as lactate, acetate and propionate. These metabolic acids can diffuse through hard and soft tissues to produce a variety of biological effects in the pathogenesis of dental caries, gingivitis, and periodontitis. This clinical study evaluated the effect of rinsing with LISTERINE®, with or without fluoride, on plaque metabolic acid production and plaque pH response after a sucrose challenge.1

This was an observer-blind, randomised study using a three-way crossover design. Twenty four subjects rinsed with 20 ml of one of the following rinses twice daily for 16 days for 30 seconds:1

  • LISTERINE® (essential oil mouth rinse)
  • LISTERINE® containing fluoride (essential oil mouth rinse plus 100 mg/kg fluoride)
  • negative control

On day 17, 1 hour after the last mouth rinse, subjects rinsed with 20 ml of 10% sucrose solution for 1 minute.  Seven minutes after the sucrose challenge, supragingival plaque was collected from molar and premolar teeth. Plaque pH and metabolic acid ions were analysed using a micro pH electrode and capillary electrophoresis respectively.1

The results showed that after rinsing with LISTERINE®, dental plaque produced 36% less lactate, 36% less acetate and 44% less propionate than after the negative control rinse. The dental plaque exhibited a pH 0.42 higher after rinsing with LISTERINE®than after the negative control rinse. These results were not affected by the addition of 100 mg/kg fluoride.1

The authors concluded that “this EO antiseptic mouth rinse [LISTERINE®], with or without fluoride ion, is effective in reduction of plaque acidogenicity after a sucrose challenge.”1

In a second study, the effect of two mouth rinses on salivary pH* was studied. This cross-sectional study used 2 mouth rinses, LISTERINE® and Periobacter®, with water as a negative control.2

Patients were stratified by age: 21–30, 31–40 and 51–60 years old, with 10 adults in each group. Samples were collected at 9 am following breakfast and tooth brushing. Whole unstimulated saliva was collected and pH and buffer capacity was determined.

Samples were taken immediately after washing the mouth with the corresponding mouth rinse, 5 minutes later and then at 15, 25 or 35 minutes until pH had recovered; and finally 15 minutes after recovery of the initial pH. All saliva samples were immediately analysed in full triplicate. Block ANOVA and Pearson test were applied for the analysis.2

The results showed that LISTERINE® and Periobacter®, despite their acidic pH value, produce an immediate increase in the salivary pH value (p< 0.0001); most of the subjects recovering to the initial pH before 15 minutes post-rinsing. The buffering capacity was higher in adults 31–40 years old (p<0.05).2

In conclusion, LISTERINE was shown not to adversely affect salivary pH.2


  1. Zhang JZ et al. Effect of an essential oil mouthrinse, with and without fluoride, on plaque metabolic acid production and pH after a sucrose challenge. Caries Res 2004; 38: 537–541.
  2. Belardinelli P et al.  Effect of two mouthwashes on pH and salivary nitrite concentration. IADR meeting Barcelona, Spain, July 14-17, 2010. Abstract #1051.