Human Salivary Buffering Rate Measured in Situ in Response to an Acid Stimulus Found in Some Common Beverages

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Abstract
Normal "resting" salivary pH was detd. with a Beckman Model G pH electrometer using an in situ glass (H+) electrode placed anteriorly under the tongue with the calomel electrode in contact with the skin of the hand. The avg. normal pH of 195 subjects was 5.97, S. D. [plus or minus] 0.40, S. E. -0.022, over a range of 5.73-6.15, and with a symmetrical frequency distr. Temp. control and absence of CO2 loss probably contributed to a higher (H+) concn. and a smaller range than is usually found. Measurement of 3 normal values before the ingestion of 3 oz. of 1 of 10 stimulant and 2 control beverages were made in 385 individual expts. Readings of pH values were taken within 12 sec. after drinking the beverage and every 20 sec. thereafter until the salivary pH returned to or above the avg. normal. A return within the avg. 2-min. run was designated as a positive buffering response. The pH shift toward alkalinity during the avg. expt. was rapid and statistically significant when the slope of the curves for the beverages was compared with the slope of the control curves. Of the total group, 52.8% showed a positive buffering response within 12 sec., 70% in 30 sec., and 96% in 2 min. Heavy smokers showed a 20% consistently slower rate of buffering response. This depression of the salivary reflex was ascribed to nicotine inactivation of the taste receptors.

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