Acid-Base Properties of Human Gingival Crevicular Fluid

The pH of human gingival crevicular fluid (GCF) has been reported by many authors to be very alkaline (pH 7.5 - 8.7). This alkalinity could be explained, at least partially, by the fact that all measurements were performed either at low Pco, or in the absence of CO 2 . Therefore, we set up a procedure which allows for measurement of the pH of GCF samples from single inflamed sites at controlled Pco 2 . At a Pco 2 of 4.7 kPa (= 35 mmHg) and at 37 °C, the pH was 7.96 ± 0.10 (SEM, n = 9), a value which differs significantly from the value of 8.38 ± 0.09 measured in the absence of CO 2 in the same samples. The non-bicarbonate buffer value of the sample determined by CO 2 titration was 6.0 slykes. It is because this value is low that pH varies so greatly with Pco 2 . At physiological Pco 2 , the total buffering power becomes very high above pH 8.0, because of the high bicarbonate concentration.