For some random reason, about half-an-hour ago I wondered how toothpastes that claim to treat sensitive teeth work. Admittedly, half an hour on the web hardly qualifies me as an expert – a shame as dentists earn more than research scientists. But as far as I can see it seems that nobody really knows with real certainty.

However, it is easy to find out what the active ingredients are, for the Sensodyne brand: Potassium nitrate, strontium acetate, and in one case that may be new isopropane.

Isopropane caught my eye, it is a very simple molecule, that is basically halfway between the natural gas that powers your cooker and the petrol that powers your car. It is a very simple molecule of carbon and hydrogen that is just about a liquid at standard British room temperature, it boils at 28 C. I have no reason to think it does not work, but well done to the companies for adding a molecule that is simpler than petrol to toothpaste and selling it for £4 for 100 ml.

Anyway, the working hypothesis in the field appears that in sensitive teeth there are tiny holes and that flow of presumably saliva or whatever along them can reach nerves in the teeth and stimulate them – causing pain.

So, you can try potassium nitrate. Nerve impulses travel along nerves a bit like waves along a water canal but the things that go up and down are not the height of water but concentrations of ions (= charged atoms and molecules in the water). One of these ions is potassium so ramping up the potassium concentration could potentially hinder the nerve impulses that are sensed as pain.

If you look at a periodic table you will see that strontium is just below calcium – which means it is chemically similar. Your teeth are mainly calcium phosphate so if you want to encourage more crystallisation to fill in holes in your teeth, an element close to the element in your teeth makes sense.

And if all else fails Al-Azzawi and Dayem study blasting the tooth with a neodymium-YAG laser (YAG = yttrium–aluminium-garnet). I’ll stick with my trusty toothbrush.