Effects of Glucose and Urea on Dental Deposit pH in Dogs

The pH of deposits that formed on the maxillary incisors, canines, and premolars of adult beagles 1, 3, and 20 weeks after prophylaxis was measured before and after the application of 5 % glucose or 5 % urea solutions. The pH decreased between 0.23 and 1.68 units after glucose, and increased between 0.69 and 1.96 units after urea. The effect of carbohydrate on plaque pH has been studied in humans'-3 and mon-keys.4-6 Kleinberg7 demonstrated that the effects of glucose on in vitro plaque corre-lated with his clinical experiments. He used solutions of glucose that ranged from 0.1 to 50%, and found that maximum pH changes occurred with 5 % glucose, usually within five minutes of application. Although a number of carbohydrates3,48 can alter the pH of dental plaque, glucose was se-lected for our studies because of its im-portance both to cellular metabolism in general and to oral bacteria in particular. In 1967, Kleinberg9 demonstrated the effect of urea on plaque pH in situ. He used solutions of urea that ranged from 0.17 to 16.7 % and found that maximum responses were uniformly observed with solutions between 5 and 10 % within the first ten minutes of application. Since the methodology was similar to that used in his glucose experiments, he was able to com-pare plaque responses to glucose and urea. It was concluded that with the same sub-trate conditions, the affinity of plaque for glucose is less than that for urea. The purpose of this investigation was to determine if the dental deposits in adult, Portions of this paper were presented at the 49th gen