An in vitro Simulation of the Effects of Chewing Sugar-free and Sugar-containing Chewing Gums on pH Changes in Dental Plaque

The objective ofthese studies was to simulate the effect of chewing sugar-free and sucrose-containing chewinggums on the return of the pH to neutrality after exposure to sucrose of plaque located on the buccal (BLM) and lingual (LLM) surfaces ofthe lower molar teeth. In study 1, a 0.5-mm-deep artificial plaque containing Streptococcus oralis cells was exposed to 10 % sucrose for one min, and a 0.1-mm-thick film of sucrose-free artificial saliva was then flowed over the plaque surface at the unstimulated sali-vary film velocities previously found at the BLM and LLM sites. At the time ofthe pH minimum (pH 4-5), one ofthree conditions was simulated: (a) a no-gum-chewing control, or chewing for 20 min on either (b) a sugar-free gum or (c) a sucrose-containing gum. The recovery of the plaque pH to resting values was rapid during simulation of chewing a sugar-free gum (SFG), much slower with the no-gum control, and even slower with simulation of chewing a sucrose-containing gum (SCG). The pH recovery was slower with the BLM than theLLM plaque. In study 2, the BLM plaque was exposed to a 2 % sucrose solution for 20 min under stimulated salivary conditions, to simulate the consumption of a meal, followed by one of conditions (a), (b). or (c) described above. The pH recovery with simula-tion of chewing a SCG was faster than with the no-gum control, but much slower than with the SFG simulation. In study 3, when both BLM and LLM plaques were exposed for 20 min to the sucrose levels in chewing-gum-stimulated saliva and then unstimulated conditions were simulated, the pH fall and recovery were similar to those found by others in vivo. From the results ofthese studies, it would be expected that when the plaque pH has fallen, after exposure to fermentable carbohydrate, it would return to neutrality more readily with the use of sugar-free rather than sucrose-containing gums