Your teeth are not naturally pure white. They have layers, and what happens to these layers over time decides their color.

1. Teeth have layers (this is the core science)

• Enamel – the outer white layer (thin and semi-transparent)




• Dentin – the inner layer, which is naturally yellowish

As long as enamel is thick and healthy, teeth look white.
When enamel thins or stains, the yellow dentin shows through more clearly.

That’s why teeth yellowing is often structural, not just dirty.

Main scientific reasons teeth turn yellow 1. Enamel thinning with age

As we age:

• Enamel slowly wears down




• Dentin becomes more visible
  Even with perfect brushing, age alone can make teeth look yellow

2. Extrinsic stains (outside stains)

These sit on the enamel surface and are caused by:

• Tea & coffee




• Cola & energy drinks




• Red wine




• Tobacco / smoking




• Poor rinsing after meals

These stains can usually be removed with scaling or whitening.

3. Intrinsic discoloration (inside the tooth)

This is deeper and harder to reverse. Causes include:

• Certain medicines (especially tetracycline taken in childhood)




• High fluoride exposure




• Childhood illness or fever




• Trauma to teeth




• Genetic factors (some people naturally have yellower dentin)

Dentists confirm this classification in research indexed on PubMed.

4. Acidic & processed foods

Frequent intake of:

• Citrus fruits in excess




• Soft drinks




• Packaged acidic foods

These erode enamel, making teeth look yellower even if they’re clean.

5. Dry mouth & saliva chemistry

Saliva helps neutralize acids and wash away stains.

• Low saliva flow




• Mouth breathing




• Certain medications

→ increase staining and enamel damage