Question

How does acid affect teeth?

Answer 1

Hint: Our tooth enamel is majorly made up of minerals and ions such as calcium and phosphate which provide strength to our teeth. The enamel is the outermost protective layer of our teeth. Acids or acid-containing substances result in demineralization and hence tear away the enamel.

Complete step-by-step answer:Human teeth are made of four different tissues – enamel, dentin, cementum, and pulp. Here we only need to consider the first type of tissue, that is, enamel.
Enamel is the outermost hard covering of the teeth. It is the hardest tissue in the human body as it is mostly made up of inorganic materials and strong minerals such as hydroxyapatite which is a mineral form of calcium phosphate. The enamel is so hard that it can withstand acid-base fluctuations and heavy forces.
But when the oral pH drops below 5.5 (too acidic), the enamel gets prone to demineralization. Demineralization is the process of dissolution or loss of the minerals by the action of acid. When there is an excess of acid in the mouth, the phosphate from hydroxyapatite crystals combines with an acid to form hydrogen phosphate species which then dissolves.
The reaction involved is given below, according to it when the amount of acid becomes high the reaction will proceed in the forward direction and calcium ions will continue to remove from the mineral. Thus, the tooth enamel becomes more prone to decay which can result in the formation of cavities, sensitivity in teeth, discoloration of teeth, etc.
     \[\begin{align}
  & \text{C}{{\text{a}}_{10}}{{\left( \text{P}{{\text{O}}_{4}} \right)}_{6}}{{\left( \text{OH} \right)}_{2}}+14{{\text{H}}^{+}}\rightleftharpoons 10\text{C}{{\text{a}}^{2+}}+6{{\text{H}}_{2}}\text{PO}_{4}^{-}+2{{\text{H}}_{2}}\text{O} \\
 & \text{Hydroxyapatite}+\text{Hydrogen}{{\text{n}}^{+}}\rightleftharpoons \text{Calciu}{{\text{m}}^{2+}}+\text{Phosphoric acid}+\text{Water} \\
\end{align}\]
Hence, acid can cause tooth decay when present in excess amounts inside our mouth.

Additional information: To prevent tooth decay we should use a toothpaste containing fluoride, brush carefully, reduce sugar intake and consume calcium and vitamins.

Note: The saliva in our mouth acts as a buffer to maintain the neutral pH of our mouth by adding back the minerals to partially dissolved enamel when the acidic substance is removed, and the pH level reaches the value of 7. But the excess intake of acidic substances or sugars and irregular brushing will surely result in enamel decay as the condition for remineralization cannot be fulfilled.