Which is the hardest material of the human body?

The narrower distal end of the stomach is called:

Human teeth are:
$(1)$ Of different types.
$(2)$ Embedded in a socket of the jaw bone.
$(3)$ Formed in two sets during their life.
This type of dentition is called:

Bulk of the tooth in mammals is made up of

The water content in enamel is approximately .......

The primary dentition in human differs from permanent dentition in not having one of the following type of teeth.