Journal of Dental Research, Vol 65, 44-48, Copyright © 1986 by International & American Associations for Dental Research Online Journals
In vivo measurements of sulcal plaque pH in rats after topical applications of xylitol, sorbitol, glucose, sucrose, and sucrose plus 53 mM sodium fluoride
A. R. Firestone and J. M. Navia
In two series of experiments, Sprague-Dawley-derived rats were infected
orally with cariogenic micro-organisms and fed caries-promoting diets. By
means of an antimony electrode, resting pH values were measured in the
mesial sulcus of the maxillary left first molar. 100 or 200 microL of the
test solutions were applied, and the change in pH (delta pH) was recorded
for three min. Test solutions were: (a) 10% sucrose, 10% glucose, 10%
sorbitol, or 10% xylitol; (b) 0%, 10%, 20%, or 40% sucrose; (c) 0%, 3%, 7%,
or 10% sucrose; and (d) 10% sucrose, 10% sucrose + 53 mmol/L NaF (1000
ppmF-), or 10% sucrose + 53 mmol/L NaCl. Experimental design was a 4 X 4
Latin square (a, b, c) or a cross-over design (d). Solutions of sucrose and
glucose gave significantly greater decreases in pH than did sorbitol or
xylitol. pH fall was maximal for 10% sucrose and significantly less for 40%
sucrose during the three-minute experimental period. For sucrose solutions
ranging in concentration from 3 to 10%, pH fall was highest after
application of 10% sucrose when plaque was previously rinsed with water,
but this pH fall did not differ significantly from that obtained using a 7%
sucrose solution. Adding 1000 ppmF- to a 10% sucrose solution caused an
increase in pH. Rinsing the teeth to remove saliva resulted in
significantly lower resting pH values. The results of these experiments are
in agreement with the results of human plaque pH measurements.
