Effect of urea in sugar-free chewing gums on pH recovery in human dental plaque evaluated with three different methods.

The aim of this investigation was to study the effect of sugar-free chewing gums containing various amounts of urea on the pH recovery in dental plaque. Three plaque-measuring methods were used, i.e., the telemetric, the microtouch, and the sampling methods. The subjects who had refrained from toothbrushing for 3-7 days rinsed with either 10 or 50% (w/v) sucrose solutions and then chewed for 10 min: (1) one piece of chewing gum in a series of six tests in which the urea content increased from 10 to 80 mg per piece of gum: (2) one or two pieces of gum containing 20 mg urea, and (3) one, two, or three pieces of gum, one after the other, containing 20 mg urea. In some of the test series, a conventional sugarless gum was used as a control. A quick rise in plaque pH was found with all urea-containing chewing gums within the first minutes of chewing, and neutralization continued during the whole 10-min chewing periods. Higher concentrations of urea resulted in more pronounced pH recovery. Slightly higher plaque pH values were found when chewing on two pieces at a time of a 20-mg urea gum was compared with only one piece. Significantly higher pH values were recorded when using three pieces of chewing gum, one after the other (10 + 10 + 10 min), as compared with two pieces (10 + 10 min) or just one piece (10 min). In conclusion, all sugar-free chewing gums tested, particularly the urea-containing ones, initiated a pronounced pH recovery in dental plaque when chewed after a sucrose rinse.(ABSTRACT TRUNCATED AT 250 WORDS)