Plaque pH measurements by different methods on the buccal and approximal surfaces of human teeth after a sucrose rinse.

Changes in plaque pH after a sucrose rinse were simultaneously monitored by plaque sampling, touching of the plaque with antimony and glass electrodes, and telemetry. The minimum pH at approximal sites was approximately 0.7 pH units lower than that on buccal surfaces. The pH at the approximal site remained below resting levels after 120 min, and the area under the pH response curves from this site was five times greater than that from the buccal surfaces.