The Buffer Capacity of Saliva as a Measure of Dental Caries Activity

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Abstract
Fifty patients with varying amounts of dental caries were arbitrarily selected following a medical, dental, and dietary history supplemented by laboratory studies for caries activity. The patients were divided into 3 groups, the criteria being nutritional status and degree of caries activity. Group 1 contained 16 nutritionally deficient, but relatively caries-free patients; Group 2 contained 20 well nourished patients with moderate caries activity; and Group 3 contained 14 well nourished patients with rampant caries. Paraffin-stimulated saliva, collected from each of the 50 patients, was tested for dental caries activity by the chemical method of Fosdick, Hansen, and Epple, the bacteriological method of Hadley, and a method developed by the authors which measured the buffer capacity of the saliva. The latter method consisted of taking the pH reading, using a Beckman pH meter, of a 5 ml. sample of saliva. Then, from a burette calibrated to deliver 0.04 ml. per drop, 0.1 N lactic acid was added a drop at a time and a pH reading taken after the addition of each drop. The resultant readings were used to form a titration curve. The amt. of lactic acid required to lower the pH of the saliva sample from pH 7 to pH 6 was regarded as the measure of the buffer capacity of the saliva. A definite and readily discernible difference was found to exist between the buffer capacity of the saliva of a caries-immune and a caries-susceptible individual. The results achieved with the buffer capacity method correlated highly with the chemical and bacteriological tests for caries activity on the same samples of saliva, as well as with the findings obtained with the mouth mirror, exploring tine, and dental x-ray. The buffer capacity test also offered an explanation for the few instances of noncorrelation between the chemical and bacteriological tests. Malnourished patients, relatively free of dental caries, had the highest buffer capacity in the saliva, the lowest number of Lactobacillus acidophilus, and the least active Fosdick detns.; the well nourished patients with either moderate or rampant caries showed a progressive decrease in the buffer capacity of the saliva, and corresponding progressive increases in the Lactobacillus counts and the Fosdick detns.

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