What's In Your Mouth?
To understand what happens when your teeth decay, it's helpful to
know what's in your mouth naturally. Here are a few of the elements:
Your mouth and teeth are constantly bathed in saliva. Although we never
give much thought to our spit, this simple fluid is remarkable for what
it does to help protect our oral health. Saliva keeps teeth and other
oral tissues moist and lubricated, washes away some of the food
particles left behind after we eat, keeps acid levels in the mouth low,
and protects against some viruses and bacteria.
Plaque appears as a soft, gooey substance that sticks to the teeth a
bit like jam sticks to a spoon. It is, in fact, colonies of bacteria,
protozoa, mycoplasmas, yeasts and viruses clumping together in a
gel-like organic material. Also in the mix are bacteria byproducts,
white blood cells, food debris and body tissue. Plaque grows when
bacteria attach to the tooth and begin multiplying. Plaque starts
forming immediately after a tooth is cleaned; it takes about an hour
for plaque to build up to measurable levels. As time goes on, different
types of microorganisms appear, and the plaque thickens.
If left alone long enough, plaque begins to mineralize and harden into
calculus or tartar because the plaque absorbs calcium, phosphorus and
other minerals from saliva. These minerals form crystals and harden the
plaque structure. New plaque forms on top of existing calculus, and
this new layer can also become calcified.
We have many different strains of bacteria in our mouths. Some bacteria
are good; they help control destructive bacteria. When it comes to
decay, Streptococcus mutans is the bacterial strain that does the most damage. It attaches easily to teeth and produces acid.
How Your Teeth Decay
You need food, particularly sweet and sticky food, for the bacteria
in your mouth to produce acids that will attack the tooth enamel (outer
surface of the tooth). Sugars, especially sucrose, react with bacteria
to produce acid. The acid from the bacteria can decay your teeth.
It's not just candy and ice cream we're talking about. All
carbohydrate foods, as they are digested, eventually break down into
simple sugars, such as glucose and fructose. Some of this digestion
begins in the mouth. Foods that break down into simple sugars in the
mouth are called fermentable carbohydrates. These include the obvious
sugary foods, such as cookies, cakes, soft drinks and candy, but also
pretzels, crackers, bananas, potato chips and breakfast cereals. The
sugars in these foods combine with the bacteria normally in the mouth
to form acids. These acids cause the mineral crystals inside the teeth
to begin to dissolve.
The dental caries lesion forms when these acids start to dissolve a
tooth's outer protective layer, the enamel. A cavity forms when the
tooth decay breaks through the enamel to the underlying layers of the
tooth. You can reverse a caries lesion (before it becomes a cavity) by
using a variety of fluoride products. These include fluoridated water,
fluoride rinses for use at home, and, of course, any commonly used
Every time you eat, the bacteria in your mouth produce acid.
Therefore, the more times you eat the more times your teeth are exposed
to an acid attack.
Types and Stages of Decay
Dental decay, also known as dental caries, begins first inside the
tooth. A white spot appears on the enamel where the tooth has started
to weaken inside. At this stage, the tooth can repair the weakened area
with the help of fluoride and minerals in saliva. But if the decay
continues and breaks through the surface of the enamel, the damage is
permanent. The decay must be cleaned out and the cavity filled by a
dentist. Left untreated, the decay will worsen and destroy a tooth all
the way through the outer enamel layer, through the inside dentin layer
and down to the pulp or nerve of the tooth.
In young children, teeth that have recently emerged have weak enamel
and are highly susceptible to acid decay. A type of decay called baby
bottle tooth decay or early childhood caries
destroys enamel quickly and is common in children. This type of decay
can eat through enamel and leave a large cavity in a matter of months.
Older adults sometimes have chronic caries: cavities that don't seem
to get any worse or do so at a very slow rate. Teeth with chronic
caries will tend to be darker in color because the edges of the
cavities become stained from normal eating and drinking.
Root caries (decay in the roots of the teeth) is more common in
older adults. Older adults are more likely to have gums that have
receded from years of hard brushing or periodontal disease. They also
are more likely to have dry mouth (xerostomia),
which increases the risk of decay. Dry mouth is caused by many common
medicines. Be sure to ask the doctor or pharmacist if any of your
medicines cause dry mouth.
Decay can form beneath fillings or other restorations, such as crowns.
Sometimes, bacteria and food particles can slip into a tooth if a
filling hasn't been placed properly or if the filling cracks or pulls
away from the tooth, leaving a gap.
Do you or your family members get cavities frequently? Dental
research has identified factors that increase your risk of getting
decay. Next time you visit the dental office, ask about your risk
factors and discuss the best ways to reduce your risks and limit dental
To prevent your teeth from decaying, you can do two things —
strengthen your teeth's defenses with fluoride and sealants, and reduce
the number of bacteria in your mouth.
Fluoride strengthens teeth by penetrating the tooth structure and replacing lost
minerals to repair acid damage. Everyone should brush with a fluoride
toothpaste every day. Dental offices sometimes recommend additional
toothpastes, gels and mouthrinses for both children and adults.
Sealants are protective coatings placed over the tops of chewing
teeth — molars and premolars. They block bacteria and acids from
sticking in the tiny grooves on the chewing surfaces of these teeth.
Children should get sealants soon after their teeth erupt into the
Although you can never get rid of all the bacteria in your mouth, you can control bacteria by brushing regularly and flossing daily, seeing your dentist and dental hygienist
regularly for a thorough cleaning and check-up, and reducing the number
of times each day that you consume fermentable carbohydrates.
Some prescription mouthwashes (those that contain chlorhexidine) can
help prevent decay by reducing the number of bacteria in the mouth.
Chewing sugarless gums, especially those with xylitol, can help reduce
decay and increase the flow of saliva.
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