Question

Tooth-enamel is made up of :

• A. Calcium phosphate
• B. Calcium carbonate
• C. Calcium fluoride
• D. Potassium

Hint:

Tooth enamel starts corroding when the pH inside the mouth drops below 5.5.
Using fluoride toothpaste helps by converting hydroxyapatite into fluorapatite [\(Ca_5(PO_4)_3F\)], which is even harder and more resistant to acid attacks.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the primary chemical compound that makes up human tooth enamel, which is the protective outer layer of the teeth.

Step 2: Key Formula or Approach:
Identify the mineral composition of tooth enamel. Enamel is mostly comprised of a crystalline form of calcium phosphate.

Step 3: Detailed Explanation:

• Tooth enamel is the hardest, most highly mineralized substance in the human body.

• It is composed of approximately \(96\%\) minerals, with the remaining portion consisting of water and organic material.

• The primary mineral component is hydroxyapatite, which is a crystalline form of calcium phosphate with the chemical formula:
\[ Ca_5(PO_4)_3OH \] - Sometimes it is written as \(Ca_{10}(PO_4)_6(OH)_2\).

• Although this mineral is highly insoluble in water, it can undergo demineralization (decay) in acidic environments.

• When we eat sugary food, bacteria present in our mouth ferment the sugars and produce organic acids.

• If the pH in the mouth falls below 5.5, these acids react with the calcium phosphate of the enamel, causing it to dissolve (tooth decay):
\[ Ca_5(PO_4)_3OH\text{(s)} + H^+\text{(aq)} \to 5Ca^{2+}\text{(aq)} + 3HPO_4^{2-}\text{(aq)} + H_2O\text{(l)} \] - This is why brushing with basic toothpaste is recommended to neutralize the acids and protect the enamel.


Step 4: Final Answer:
Tooth-enamel is made up of calcium phosphate.