THE DISTRIBUTION OF SALIVA AND SUCROSE AROUND THE MOUTH DURING THE USE OF CHEWING GUM AND THE IMPLICATIONS FOR THE SITE-SPECIFICITY OF CARIES AND CALCULUS DEPOSITION

Over a 20-minute period, subjects expectorated 8 samples of whole saliva (EWS) while chewing gum. Flow rates were calculated, and sucrose was analyzed in these samples as well as in saliva collected on filter paper strips from different tooth surfaces. Salivary film velocity (SFV), based on a 0.1-mm-thick film, was estimated from the clearance half-times of KCl in agarose disks positioned in different regions of the mouth. Salivary flow rate peaked at 5.1 mL/min in the first min but fell to about 1.25 mL/min by the end of the 20 min of gum-chewing. In contrast, flow rate when subjects sucked sour lemon drops averaged about 5.3 mL/min throughout the 20-minute period. The mean salivary sucrose concentration during gum-chewing peaked in the second min at 384 mmol/L (13. 1%) but had fallen to 14 mmol/L by the 15-20-minute time interval. The sucrose concentrations on the palatal surfaces of the upper incisors and the facial and lingual surfaces of the lower molars were not significantly different from that in EWS but were much lower on the facial surfaces of the upper incisors and molars, and on the lingual surfaces of the lower incisors. When flow was unstimulated, SFV was 0.8-1.0 mm/min on the facial surfaces of the upper incisors and lower molars but about 5-8 mm/min on the facial surfaces of the upper molars and on the lingual surfaces of the lower incisors and molars. During chewing-gum use, the SFV increased only to 4 and 10 mm/min on the facial surfaces of the upper incisors and lower molars, respectively, but on the facial surfaces of the upper molars and on the lingual aspects of the lower incisors and molars, it became equivalent to that in a well-stirred solution. This study showed that even during gum-chewing, which would be expected to facilitate the mixing of the different salivary secretions, the saliva provided a series of distinctly different fluid environments, some with cariogenic and others with calculogenic potential, for plaque in different regions of the mouth.