Effects of Milk on pH of Plaque and Salivary Sediment and the Oral Clearance of Milk

A micro-glass electrode was used intra-orally to monitor pH changes in 3-day-old plaque after rinses with 5% sucrose, 5% lactose, milk or milk plus 4 ppm fluoride. Changes in pH were also followed in salivary sediment/substrate mixtures. Both methods ranked milk as least acidogenic, e. g. in 8 of 9 subjects pH 5.2 was reached in 3 min after a sucrose, but in only 1 subject in 6 min after a milk rinse. About 0.3 ml milk remained in the mouths of dentate subjects 10 min after drinking milk. With salivary sediment the addition of 5% sucrose, 5% lactose, chocolate or strawberry flavour to milk increased pH changes over those of milk alone. Milk often produced an initial rise in pH. With sucrose the pH began to fall immediately. The addition of 4 ppm fluoride to milk had no appreciable effect on the pH changes in plaque or sediment.