if mercury is harmful for our body , then why do we use amalgam which also contain mercury for filling of teeth cavities ?

Dental amalgam is a mixture of mercury and a silver–tin alloy.

Adavantages:

• The amalgam filings are strong and long-lasting than other types of filings.
• It is least expensive filling material.

Disadvantages:

• Since it contains the element mercury it liberates very low levels of mercury that can be inhaled.
• Exposure to high levels of mercury vapour are associated with severe effects in the brain and the kidneys.