What’s in Your Toothpaste?

by DAVID BODANIS

 Into the bathroom goes our male resident, and after the most pressing need is satisfied it’s time to brush the teeth. The tube of toothpaste is squeezed, its pinched metal seams are splayed, pressure waves are generated inside, and the paste begins to flow. But what’s in this toothpaste, so carefully being extruded out?

  Water mostly, 30 to 45 percent in most brands: ordinary, everyday simple tap water. It’s there because people like to have a big gob of toothpaste to spread on the brush, and water is the cheapest stuff there is when it comes to making big gobs. Dripping a bit from the tap onto your brush would cost virtually nothing; whipped in with the rest of the toothpaste the manufacturers can sell it at a neat and accountant-pleasing $2 per pound equivalent [Today, it would be $14 per pound.] Toothpaste manufacture is a very lucrative occupation.

      Second to water in quantity is chalk: exactly the same material that school teachers use to write on blackboards. It is collected from the crushed remains of long-dead ocean creatures. In the Cretaceous 2seas chalk particles served as part of the wickedly sharp outer skeleton that these creatures had to wrap around themselves to keep from getting chomped by all the slightly larger other ocean creatures they met. Their massed graves are our present chalk deposits.

      The individual chalk particles—the size of the smallest mud particles in your garden—have kept their toughness over the aeons, and now on the toothbrush they’ll need it. The enamel outer coating of the tooth they’ll have to face is the hardest substance in the body—tougher than the skull, bone, or nail. Only the chalk particles in the toothpaste can successfully grind into the teeth during brushing, ripping off the surface layers like an abrading wheel grinding down a boulder in a quarry.

      The craters, slashes, and channels that the chalk tears into the teeth will also remove a certain amount of build-up yellow in the carnage, and it is for that polishing function that it’s there. A certain amount of unduly enlarged extra-abrasive chalk fragments tear such cavernous pits into the teeth that future decay bacteria will be able to bunker down there and thrive; the quality control people find it almost impossible to screen out these errant super-chalk pieces, and government regulations allow them to stay in.

     In case even gouging doesn’t get all the yellow off, another substance is worked into the toothpaste cream. This is titanium dioxide. It comes in tiny spheres, and it’s the stuff bobbing around in white wall paint to make it come out white. Splashed around your teeth during the brushing it coats much of the yellow that remains. Being water soluble it leaks off in the next few hours and is swallowed, but at least for the quick glance in the mirror after finishing it will make the user think his teeth are truly white. Some manufacturers add optical whitening dyes—the stuff more commonly found in washing machine bleach—to make extra sure that that glance in the mirror shows reassuring white.

      These ingredients alone would not make a very attractive concoction. They would stick in the tube like a sloppy white plastic lump, hard to squeeze out as well as revolting to the touch. Few consumers would savor rubbing in a mixture of water, ground up blackboard chalk, and the whitener from latex paint first thing in the morning. To get around that finicky distaste the manufacturers have mixed in a host of other goodies.

      To keep the glop from drying out, a mixture including glycerin glycol—related to the most common car antifreeze ingredient—is whipped in with the chalk and water, and to give that concoction a bit of substance (all we really have so far is wet colored chalk), a large helping is added of a gummy molecule from the seaweed Chondrus Crispus. This seaweed ooze spreads in among the chalk, paint, and antifreeze, then stretches itself in all directions to hold the whole mass together. A bit of paraffin (the fuel that flickers in camping lamps) is pumped in with it to help the moss ooze keep the whole substance smooth.

     With the glycol, ooze, and paraffin we’re almost there. Only two major chemicals are left to make the refreshing, cleansing substance we know as toothpaste. The ingredients so far are fine for cleaning, but they wouldn’t make much of the satisfying foam we have come to expect in the morning brushing.

      To remedy that every toothpaste on the market has a big dollop of detergent added too. You’ve seen the suds detergent will make in the washing machine. The same substance added here will duplicate that inside the mouth. It’s not particularly necessary, but it sells.

     The only problem is that by itself this ingredient tastes, well, too like detergent. It’s horribly bitter and harsh. The chalk put in toothpaste is pretty foul-tasting too for that matter. It’s to get around that gustatory discomfort that the manufacturers put in the ingredient they tout perhaps most of all. This is the flavoring, and it has to be strong. Double rectified peppermint oil is used—a flavorer so powerful that chemists know better than to sniff it in the raw state in the laboratory. Menthol crystals and saccharin or other sugar simulators are added to complete the camouflage operation.

     Is that it? Chalk, water, paint, seaweed, antifreeze, paraffin oil, detergent, and peppermint? Not quite. A mix like that would be irresistible to the hundreds and thousands of individual bacteria lying on the surface of even an immaculately cleaned bathroom sink. They would get in, float in the water bubbles, ingest the ooze and paraffin, maybe even spray out enzymes to break down the chalk. The result would be an uninviting mess. The way manufacturers avoid that final obstacle is by putting in something to kill the bacteria. Something good and strong is needed, something that will zap any accidentally intrudant bacteria into oblivion. And that something is formaldehyde—the disinfectant used in anatomy labs.

      So it’s chalk, water, paint, seaweed, antifreeze, paraffin oil, detergent, peppermint, formaldehyde, and fluoride (which can go some way towards preserving children’s teeth)—that’s the usual mixture raised to the mouth on the toothbrush for a fresh morning’s clean. If it sounds too unfortunate, take heart. Studies show that a thorough brushing with just plain water will often do as good a job.

2 About 135 million years ago