Brushing teeth twice a day helps to have healthy habit. Why is it a good habit ?

Explanation

Tooth decay starts when the pH of the mouth is lower than 5.5. Tooth enamel, made up o calcium phosphate is the hardest substance in the body. It does not dissolve in water, but is corroded when the pH in the mouth is below 5.5. Bacteria present in the mouth degrades sugar and food particles remaining in the mouth and produce acids. This reduces the pH in the mouth.
The best way to prevent this is to clean the mouth each time after eating food. Using toothpastes, which are generally basic, for cleaning the teeth can neutralise the excess acid and prevent tooth decay.