Diatoms are are one of the microbes in toothpaste. Fluoride is also in toothpaste. Another microbe is Humectants. The diatoms are used to clean your teeth. Fluoride is used to protect your teeth from decaying.

Humectants are used in toothpaste to make it easy to squeeze through the tube and it is smooth ready for you.

Diatoms(in toothpaste)