Food is broken down into smaller pieces in the mouth by chewing. This is an example of mechanical digestion. The teeth cut and crush food, and the pieces are mixed with saliva to form a ball of food called a bolus.
There are different types of human teeth, with a different structure and function:
Tooth decay happens when the hard outer enamel of the tooth is damaged. This can happen when bacteria in the mouth convert sugars into acids that react with the enamel. Bacteria can then enter the softer dentine inside.
Tooth decay can be prevented by:
Fluoride compounds may be added to toothpaste and public water supplies. Fluoride reduces tooth decay by:
However, there are arguments against fluoridation of drinking water. For example: