In our survey, labelling information was not consistent. Some companies listed the amount of fluoride in ppm and some in percentages, some in both and some not at all. The British Dental Association (BDA) have recommended that all toothpastes should list their fluoride content in ppm as this is the easiest way to make the total amount of fluoride in any given product clear.

Choosing a low ppm toothpaste for your child is essential for limiting the amount of fluoride heor she ingests. Not long ago, researchers in Manchester set out to determine how much fluoride was being retained in children's mouths after brushing with toothpastes with different ppms. They tested toothpastes with 400 to 1450 ppm. The average amount of fluoride ingested per brushing was 0.42 mg when using the 1450 ppm toothpaste and 0.10 mg when using the 400 ppm toothpaste. If using the 400 ppm toothpaste twice daily, children of average weight would not ingest in excess of 0.05 mg/kg body weight (considered a 'safe' level). But using the 1450 ppm toothpaste would certainly exceed this level (Br Dent J, 1999; 186: 460-2).

Unfortunately, not all toothpaste tubes show fluoride content in ppm. Some manufacturers include percentages, which are not helpful because they do not refer directly to the amount of fluoride in the tube. In fact, these percentages refer to the chemical compound of which fluoride is a part. Sodium fluoride, for example, is a compound containing sodium and fluoride whereas sodium monofluorophosphate comprises sodium, fluoride and phosphate.

To figure out the amount of fluoride in your toothpaste, you need to look for the ppm. If your toothpaste tube only lists percentages, there is a way to translate this to arrive at the amount of fluoride in the tube. The following chart will help you work out the approximate ppm of your toothpaste:

Sodium Sodium mono

ppm fluoride fluorophosphate

1500 0.32% 1.14%

1000 0.22% 0.76%

500 0.11% 0.38%

To find out how many milligrams of fluoride are in the tube, divide the ppm by 1000, then multiply that by the number of millilitres in the tube. Thus:

1500 ppm Ö 1000 x 125 ml = 187.5 mg

As a rough guide, in each 100 ml tube of toothpaste, there are the following amounts of fluoride:

ppm mg/100 ml

1500 150

1000 100

500 50

Why is there so much fluoride in toothpaste and mouthwash? Because these products are meant to be rinsed out of the mouth, so it is thought that we only retain a proportion of the fluoride. That idea, of course, is only relevant to the laboratory. In the real world, children don't always spit toothpaste out. They may be too young to control their swallowing or it may simply be that sweet flavours and pretty colours make toothpaste as appealing as candy to swallow.

Also, fluoride can be unstable. Depending on the formulation, the amount of fluoride in toothpaste can deteriorate rapidly. When sodium fluoride is combined with aluminium and/or calcium containing abrasives, the mixture will lose between 60 to 90 per cent of the added fluoride after one week's storage at room temperature (J Dent, 1989; 17: 47-54). Manufacturers may add more of it to overcome this problem.