With more councils voting to remove fluoride from drinking water recently, it's worth revisiting exactly why was added in the first place.

So what is fluoride, how does it work — and if you don't have access to fluoridated water, what else can you do to protect your teeth?

What is fluoride?

Fluoride is a form of the element fluorine: fluoride ions are fluorine atoms with an extra electron, making them negatively charged.

Fluoride ions occur naturally in rocks and minerals, and from there they dissolve easily into water, according to Laurence Walsh, a dentistry researcher at the University of Queensland.

"You find fluoride ions in all water sources, including lakes, rivers and in the ocean," Professor Walsh says.

A number of food and drinks also contain fluoride, particularly tea, c

See Full Page