Figure 1. (a) Healthy tooth: The mineralization
and demineralization processes occur at similar
rates; (b) decaying tooth: Demineralization
occurs at a higher rate than mineralization.
creating biofilms. Biofilms form when bacteria
adhere to surfaces in some form of watery
environment and begin to excrete a slimy,
gluelike substance that can stick to all kinds of
materials. Biofilms can be formed by a single
bacterial species, but more often they are produced by many species of bacteria.
Left undisturbed, the biofilm, also known
as plaque, can turn into a harder substance
called tartar, which consists of the dissolved
tooth enamel and fluids combining to form a
sort of crust on teeth. This is what the dental
hygienist may spend time scraping off during
your periodic teeth cleanings.
To prevent plaque and tartar buildup, most
toothpastes contain a mild abrasive, which
includes one or more of the following: baking soda (sodium bicarbonate, NaHCO3),
silicon dioxide (SiO2), hydrated aluminum
oxide (Al2O3 • 3H2O), and calcium hydrogen
phosphate (CaHPO4). But you don’t want to
go overboard with the abrasive, because too
much of it could remove enamel.
Modern toothpaste came along in the 1850s
when manufacturers switched from “tooth
powders” to smooth pastes. The chemical
ingredients of modern toothpaste are part
practical and part cosmetic. For example,
To restore the tooth after bacte-
rial damage and to prevent
of the ionic
(Na2PO3F), or the compound tin(II)
fluoride, also called stannous fluo-
ride (SnF2). These ingredients pre-
vent bacteria from dissolving tooth
enamel and can help restore bone.
When fluoride ions are present
in the saliva, they replace the hydroxide ion
(OH–) in the enamel to form a new mineral,
fluorapatite (Ca10(PO4)6F2), which is more
resistant to bacterial acids.
Too much of a good thing?
Too much fluoride can cause temporarily
discolored teeth, so if you have taken fluoride
supplements and your community has fluori-
dated water, you may want to skip toothpaste
that contains this ingredient. Also, not all fluo-
ride compounds are equally effective, but the
scientific evidence currently available is not
specific enough to indicate which is best for
protecting enamel. T O O
Despite the variety of past and current
ingredients used in toothpaste, what is most
important is the physical act of brushing and
the antibacterial action of the toothpaste
ingredients. But it is also possible to go too
far by using too much antibacterial or too
much abrasive. So the best way to keep your
teeth clean and healthy is to follow the advice
of the Roman playwright Plautus (c. 250–184
B.C.): “Moderation in all things.”
Learn More About Toothpaste, American Dental
Association: http://www.ada.org/en/science-research/ada-seal-of-acceptance/product-category-information/toothpaste [accessed Nov 2016].
How Does Toothpaste Work? American Chemical
toothpaste-work.html [accessed Nov 2016].
Five Things to Know About Triclosan. U.S. Food
and Drug Administration (last updated on Sept
2, 2016): http://www.fda.gov/ForConsumers/
ConsumerUpdates/ ucm205999.htm [accessed Nov
Valerie Brown is a science writer located in Eugene,
Ore. This is her first article in ChemMatters.
Toothbrushes are the oldest
technology associated with teeth
cleaning. People have been cleaning
their teeth since at least 3000 B.C.,
first with frayed twigs and then by
chewing twigs from aromatic trees.
Our ancestors created a natural
abrasive with eggshells, as well as
oyster shells, pumice, pulverized
bones, and even the ashes of
burned ox hooves.
Toothbrushes used over the centuries, left to right:
A miswak (chewing stick); a 20th century celluloid
toothbrush; a pre-1945 rubber-tip gum stimulator; a rotary
toothbrush from the 1950s; a 1920s rubber toothbrush; a
1930s Rotor toothbrush; and another chewing stick.