Why do teeth need fillings?
If the tooth has a hole in it why can't you just leave it? It's not hurting me!
A good place to start is how teeth get holes in them in the first place....
Teeth are made up of lots of minerals like calcium, phosphate and fluoride. If you can imagine these minerals are like the bricks that make up the structure of the tooth.
These bricks can come and go depending on the acid level of the mouth. When the level becomes more acidic the minerals/bricks leave the tooth. When the level becomes neutral (more basic) the minerals/bricks go back into the tooth. The minerals can come from things like our saliva, dairy foods that have lots of calcium in them, and importantly they come from fluoridated tap water and fluoride toothpaste.