The Influence of Fruit on the pH of Dental Plaque

The diet influences the plaque pH. A low plaque pH may predispose patients to dental caries whereas a raised pH is protective. Objectives: The aim of this study was to determine whether pears, bananas, apples, mandarins and pineapples would raise the pH of plaque above the resting pH. Methods: The study was conducted under controlled conditions in a laboratory at 13h00 every day for 5 consecutive days. Twenty-two students from BDS III agreed to participate. They did not eat or drink at least 45 minutes before the experiment. The initial resting pH of plaque on the tongue was tested with Neutralit® pH strips. Thereafter they chewed a fruit for 3 minutes and measured the pH immediately and at 5-minute intervals until the pH returned to the initial resting pH. Results: Ninety two percent of the students had an initial resting pH between 7 and 7.5 (mean = 7.3). Three minutes after chewing the fruits pear increased the mean pH to 7.89 (6.5-9.5) and apple to 7.65 (5.5-9), whereas the mean pH of banana decreased to 7.22 (6-8), mandarin to 7.13 (5-8.5) and pineapple to 6.91 (5-8.5). Pear and banana never decreased the pH below 6. Six of the 22 students showed a decrease in plaque pH to 5.5 or lower with one or more of the fruits. Conclusion: Pear and banana can be recommended as a snack that will increase the pH of dental plaque and decrease the risk of developing dental caries. The plaque pH response in patients needs to be assessed to determine the cariogenicity of fruits in particular individuals.