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