White spots.

This is what the British Fluoride Society says about fluorosis (Why is there a society for fluoride?)


One of many enamel defects

Dental fluorosis appears as markings on the enamel surface of teeth. It is one of 90 or so 'enamel d efects' that may affect teeth, and is caused when children ingest excessive amounts of fluoride from all available source while their teeth - primary and permanent - are developing in the gums.

Mostly pearly white flecks visible only to experts under good lighting
In most cases, dental fluorosis appears as barely visible pearly white flecks on the surface of the tooth and is undetectable except by an expert. In other words, most people whose teeth are affected by fluorosis are unlikely to notice it. Nor are they likely to notice the majority of cases of fluorosis in other people.

We know different, are dentists cashing in? (Do those spots bother you? Video)
The people who will get the discolouring are those who look after their teeth by brushing three times a day.- those social deprived children who do not  will  not.