Why do you grind your teeth when you eat sour food ? It almost always happens that the teeth grind when eating a sour food. However, this problem is more if you eat any sour fruit. Usually the fruit is sour due to the acid in the fruit. Tamarind, for example, contains tartaric acid , which has a pH of 1.8 to 3.6 ; On average, lemons contain ascorbic acid, which indicates high levels of vitamin C , with a pH of around 2 to 2.5. Again, when the pH of the saliva of the mouth is taken to be 5.6 to 6.9 , because if the value of pH drops below 5.5 , an acidic environment is created. By creating this environment, some bacteria in the mouth, such as Streptococcus mutants , produce lactic acid from sugary foods in the process of digestion , with a pH below 5.5. When the pH of the oral environment becomes acidic, the tooth enamel is damaged and the breakdown and excretion of tooth minerals begins. So the tooth decay begins. This is called dental caries. In this case, at one stage the teeth become sensitive. It starts to shiver. The whole thing is caused by the acid released by the bacteria. However, the acids in raw fruits do not cause tooth decay because they are not cariogenic and do not cause tooth decay.