you didn't know about toothpaste

What's the connection between toothpaste and oven cleaner? Below we reveal the link, along with some other surprising truths about your toothpaste.

Supermarkets and the big chemist chains offer over 100 varieties of toothpaste, with Colgate alone offering around 45.

To help you choose, we teamed up with some dental and toothpaste experts to find out the truth behind toothpaste claims. We asked companies such as Boots, Superdrug and the big toothpaste manufacturers for the evidence to back up their claims - from teeth whitening to relief for sensitive teeth. They also dished the dirt on the ingredients you really need for your twice-daily clean. 

Read on to discover five things you need to consider before you make your next toothpaste purchase. You can read the full results of our investigation in the August 2015 issue of Which? magazine and online in our guide to choosing the best toothpaste.

1. The more fluoride the better

Fluoride is the key ingredient in toothpaste, and there's strong evidence that toothpaste with higher concentrations will be more effective at controlling decay and reducing the effects of acid erosion.

Look on the toothpaste tube for the parts per million of fluoride (ppmF-) figure. Less than 1000ppmF- is a low concentration and offers limited or no protection against decay.

1450ppmF- is generally used in over-the-counter UK toothpastes and is recommended by our experts.

Some toothpastes contain less fluoride because they're manufactured in a country such as the USA where the water is more likely to be fluoridated, and some are designed to be fluoride-free - for example, Sensodyne Original, Oral B Rembrandt Plus and Euthymol.

2. Whitening toothpastes may not be what they're cracked up to be

Our experts compared two toothpastes that make whitening claims: Macleans White & Shine and Colgate Max White One. 

Both claimed to give whiter teeth in one week, but our experts saw no evidence to support these ambitious claims. 

Teeth are not naturally white, with the bulk of their yellow hue coming from the dentine inside. Toothpaste contains abrasives such as silica and mica to remove surface stains - the type you'd get from coffee, tea and red wine.

There is limited evidence to buy a whitening toothpaste instead of a standard fluoride one, and they won't be as effective as teeth whitening (bleaching) or a clean by your dentist.

3. Sensitive teeth - different ingredients work for different people

Our experts say that the active ingredients for reducing sensitivity are potassium nitrate, stannous fluoride, arginine and calcium sodium phosphosilicate (NovaMin), although they reduce sensitivity by different mechanisms.

Different sensitivity-reducing ingredients work for different people, so try a different active ingredient if your toothpaste isn’t helping. 

You could try a cheaper toothpaste with one of the active ingredients for sensitivity listed above. To reduce sensitivity, limit acidic foods and avoid tooth-brushing straight after eating.

4. Toothpaste prices - all is not what it seems

Check the pack size. A toothpaste that looks cheap can be pricey when you calculate the price per 100ml.

For example, Colgate Max White One and Sensodyne Daily Care both cost £4 per pack, but the Colgate costs £5.33 per 100ml for the smaller pack, while the Sensodyne costs £4 per 100ml.

5. Drain cleaner in your toothpaste?

You may be left foaming at the mouth when you hear what's really in your toothpaste. 

Ingredients include sodium hydroxide or lye to neutralise the pH of other ingredients, which is also used in larger quantities in drain and oven cleaner. There's also PVM/MA Copolymer - a binder that helps the toothpaste stay on your teeth and gums, but is also found in hairspray.