Name the diseases associated with deficiency and excess of fluoride.

Explanation

### Step-by-Step Solution:

1. **Understanding Fluoride**: Fluoride is a mineral that is commonly found in drinking water and is important for dental health. It can have both beneficial and harmful effects depending on its concentration.

2. **Diseases Associated with Fluoride Deficiency**:
- **Tooth Decay**: A deficiency of fluoride can lead to an increase in dental problems, particularly tooth decay and dental caries. This is because fluoride helps to strengthen tooth enamel and makes it more resistant to acid attacks from plaque bacteria and sugars in the mouth.
- **Osteoporosis**: In severe cases, a lack of fluoride can contribute to osteoporosis, which is a condition characterized by weak and brittle bones. This can affect the jawbone as well.

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