If you do what your dentist tells you, you’ll brush your teeth at least twice a day. I do, and – like most people I use toothpaste. The other day I found myself reading the ingredients and it was quite a list. That got me thinking about the very nature of toothpaste, a substance that – to do its job – must exhibit a wide range of characteristics. So I’ve compiled a list of common toothpaste ingredients and what they do. I also stumbled upon an explanation for why the orange juice you drink after brushing your teeth tastes so foul.

You need to be able to store toothpaste in a small space (eg a tube) but spread it around a larger space (ie your mouth)
Sodium lauryl sulphate (SLS) (AKA Sodium dodecyl sulfate (SDS)) is a surfactant used in a wide variety of products including floor cleaners, shampoos, shaving foams, engine degreasers and bubble baths. In toothpaste it is used primarily as a foaming agent.

Glycerin (AKA glycerol) is a sugar alcohol. It is sweet and viscous so it’s partly there for consistency and partly for flavour.

Carrageenan is any of a family of linear sulphated polysaccharides and is used as a stabilizer, added to prevent constituents separating. Carrageenan is derived from red seaweed (Chondrus crispus) and it is a non-Newtonian fluid, specifically it is thin under shear stress and recovers its viscosity once the stress is removed. This is one reason that toothpaste is easy to squeeze out of the tube, and holds its shape somewhat when outside afterwards, but does not easily drip out of the tube if the lid is left off.

It needs to remove things that are stuck to your teeth
Hydrated silica is a form of silicon dioxide, which has a variable amount of water in the formula. It is also known as silicic acid, a term usually used for its form dissolved in water. It is found in nature, as opal, which has been mined as a gemstone for centuries and in the cell walls of diatoms. It’s used as mild abrasive (this is why toothpaste is sometimes recommended for repairing minor scratches in glass.

Mica refers to silicate minerals (which contain silica, SiO4). They are sometimes called “sheet silicates” because they form a sheet-like crystalline structure. Like
hydrated silica, mica acts as a mild abrasive to aid polishing of the tooth surface. It also adds a glittery shimmer to the paste.

Ideally it should make your teeth stronger and if possible cleaner looking
Sodium fluoride is used to enhance the strength of teeth by the formation of fluoroapatite, a naturally occurring component of tooth enamel. In theory this strengthens teeth to prevent cavities.       

Titanium dioxide is used to provide whiteness and opacity.

It should taste nice
Sodium saccharin is the sodium salt version of saccharin (AKA benzoic sulfinide). It is in toothpaste for flavour and is hundreds of times sweeter than sucrose.

See also glycerin, above.

Sorbitol (AKA Glucitol) is another sugar alcohol.

It should discourage the presence and growth of disease-causing organisms
Triclosan (AKA 5-chloro-2-(2,4-dichlorophenoxy)phenol) is a potent wide spectrum antibacterial and antifungal agent.

As for why drinking orange juice after brushing your teeth is so unpleasant, it’s almost certainly has nothing to do with the minty flavour of the toothpaste. Apparently the same unpleasant taste is experienced if you use toothpaste of any flavour (and there are loads of flavours out there), and in other contexts mint and citrus can be a very pleasant combination. It seems that sodium lauryl sulphate might hold the secret, because SLS does more than just help toothpaste lather. SLS also suppresses your sweet receptors, so basically when you drink the orange juice you can taste all the various components of the flavour, except the sweet bits.