Urea Rinse effectively Neutralises Sucrose-induced Decrease in Plaque pH

Objectives: To investigate the neutralising effects of subsequent urea rinse on sucrose-induced decrease in plaque pH with interdental plaque pH telemetry. Method: Six participants wearing partial lower prostheses which incorporated a miniature glass pH electrode were included. After 5 or 6 days of plaque accumulation on the tip of the electrode, the subjects rinsed with a 15 ml 10% sucrose solution, followed by no subsequent rinsing or rinsing with either 15 ml of water, 0.25%, 0.50% or 1.00% urea solution, for 2 min. The plaque pH was continuously recorded for 120 min. Results: Without subsequent rinsing, the plaque pH decreased at 10 min to 4.39 and stayed below the critical pH of 5.7 for 80 min following a sucrose rinse. Subsequent water rinse showed little effects on the sucrose-induced decrease in plaque pH, whereas subsequent urea rinses all immediately and effectively neutralised sucrose-induced decrease in plaque pH, and remained above the critical pH of 5.7 until the end of data collection. Conclusion: Urea rinse could effectively counteract the pH fall following sucrose administration. These results strongly suggested that the regular use of low-concentration urea rinse after carbohydrate consumption may help prevent caries. Keywords: demineralisation, plaque pH, Stephan curve, sucrose, urea