The effect of swallowing frequency on oral sugar clearance and pH changes by Streptococcus mitior in vivo after sucrose ingestion.
A theoretical study of oral sugar clearance (Caries Res 17:321-334, 1983) suggested that the unstimulated salivary flow rate (UNSTFR) and the volume of saliva present in the mouth before swallowing (VMAX) can greatly affect the rate of sugar clearance. The object of this study was to determine whether variations in UNSTFR, by water infusion into the mouth, and in VMAX, which can be altered by varying the swallowing frequency, would influence sugar clearance and whether changes in VMAX would affect the extent of the pH fall produced by S. mitior in vivo after sucrose consumption. In three experiments on each of ten adult subjects, UNSTFR was measured initially (mean value = 0.55 ml/min), and a swallowing schedule was calculated so that the volumes swallowed were either 0.3 ml or 1.0 ml. After a 10-second rinse with 20 ml of a 10% sucrose solution, the subjects maintained a swallowing frequency such that the volumes swallowed were either 0.3 ml or 1.0 ml at normal UNSTFR or were 0.3 ml when UNSTFR was increased by infusing water at 0.5 ml/min. In all subjects, clearance of sugar was faster at the higher swallowing frequency and at the higher flow rate, as predicted by the theoretical model. Small acrylic splints were made to fit over the lower incisors of ten subjects and to hold in the floor of the mouth an antimony microelectrode covered by a 0.5-mm layer of S. mitior, which was held in place by a dialysis membrane.(ABSTRACT TRUNCATED AT 250 WORDS)