Question

\[(i)\] Explain why the pH in a person’s mouth becomes lower after each meal.
\[(ii)\] What damage could be caused while the pH is low?
\[(iii)\] How could the person change his eating habits to lessen chances of suffering from tooth decay?

Answer 1

Hint: Certain foods such as sugary beverages, snacks and some grains increase the acidity in the mouth. Foods that are highly acidic, like lemons, lower the pH in the mouth, while food like melons increases the pH in the mouth.

Complete answer:
\[(i)\] The saliva pH value before the meal is $7.4$, which is basic, but after the meal the pH value of saliva becomes $5.8$ which is less than seven. After each meal, the sugar in food items will break down to corresponding acids by the action of bacteria, as acidity increases, the pH decreases. The saliva can help neutralize the acid, but eating acidic food can increase the acidity of the mouth.
\[(ii)\] When the pH is low, tooth decay can occur. The tooth decay occurs when the pH level in the mouth is $5.5$. When we consume acidic foods and drink, the pH of the mouth decreases. When the mouth undergoes dramatic or long-lasting periods of low pH, it can cause cavity-causing bacteria to grow.
\[(iii)\] This person can lessen the chances of tooth decay if he/she adds more basic food to their meals, so as to boost the alkalinity of the mouth. Some tips for increasing alkalinity are:
Eat nutritious and balanced meals and limit snacks. Avoid carbohydrates such as candy, chips or soft drinks which contain high amounts of sugar.
One should always brush their teeth twice a day after having food.
Check with your dentist about the use of supplemental fluoride, which strengthens your teeth.
Before sleeping, brushing must be done as the chances of bacterial action is more at the time of sleep.

Note:
The pH of our mouth can change according to the types of food we eat. But we tend to eat more acidic foods. Maintaining a good pH balance in the mouth allows a healthy balance of good and bad bacteria. Good bacteria protect our teeth and gums whereas bad bacteria in our mouth aid in the digestion of foods.