Measurement of pH in human dental plaque in vivo with an ion-sensitive transistor electrode

A transistor pH electrode mounted on a removable partial denture was used to measure the pH of 2- and 4-day-old approximal and occlusal plaques in 2 adults. Direct application or a mouth-rinse of sucrose, glucose or maltose to the plaque covering the electrode caused the pH to fall within 2–3 min to approx. 4.4–5.2 in both subjects. Glucosylsucrose and lactose also lowered the pH, but not below 5.5. The transistor pH electrode was found suitable to record the pH of dental plaque in vivo, and to evaluate the fermentability of sugar substitutes.