What is happening in the mouth during a meal?

Every time you eat you feed oral bacteria in your mouth. Bacteria begin with the formation of acids, that dissolve tooth enamel. Over time the saliva washes away the acid and remineralises softened tooth areas. If pH of the mouth is below 5.5, the saliva can no longer effectively remineralise teeth, which increases the risk of caries. Stephan’s curve is a graph that shows the evolution of the pH in the mouth after eating sugary foods or drinks. In the graph we can see what is going on in your mouth when you eat or drink something. On the vertical axis is the pH of the mouth. The lower the pH, the more acidic is oral cavity, the higher the pH, the more alkaline is oral cavity. Low pH of the mouth is the worse environment for our teeth. The pH of saliva is generally around 7.1, which is a slightly basic and near-neutral pH. At such pH teeth are in the most healthy environment. When we eat something, the pH in our mouth is reduced to more acidic values and when the pH drops below 5.5, the teeth begin to decompose. If teeth are exposed to constant meals throughout the day, oral environment is constantly acidic, which can dissolve teeth easily. In general, it is better to finish your chocolate bar in one meal, than eating it throughout the whole day. During the time, we do no eat, teeth are under the influence of saliva which acts protective. During the day there may be a lot of unexpected events, that can change the curve.

What factors affect the appearance of Stephan’s curve?

  1. The frequency of meals. Always when we eat carbohydrates, the pH is lowered to 5.5, bellow which teeth begin to dissolve. More frequently we eat, more likely we will develop tooth decay.
  2. Type of food. Snacks that are healthier for your teeth will do less damage. When we eat cheese, pH in the mouth does not drop significantly below 7. If you drink Coca-Cola with very acidic pH, the pH in the mouth also immediately drops.
  3. Consistency of the food. Saliva rapidly washes away liquid forms of food, while thickier and stickier food, like biscuits, caramels, bananas, etc., are very difficult to rinse away, because that kind of food adhere to teeth and remain there for a longer time. As long as the food stick to the teeth, as long it will provide nutrients to oral bacteria.
  4. Oral hygiene. If you are not brushing regularly, the teeth develop a thick layer of dental plaque. Saliva can’t neutralize acid under heavy thick plaque, so teeth are much longer exposed to a pH below 5.5.
  5. The amount of saliva. People who have a small amount of saliva, have a higher risk of caries. Saliva does not rinse away food residues, oral bacteria and acid as efficiently as it should.

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