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How Teeth Decay
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:
Saliva — 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 by
carrying immunoglobulins and other substances important for immunity.
Pellicle — Certain proteins in saliva (glycoproteins) are
absorbed by the surface of our teeth. This creates a microscopically
thin, clear coating on the teeth called "acquired pellicle." The
pellicle starts forming immediately after you brush your teeth, and,
within a few minutes, you can feel that slippery, moist feeling on your
teeth. The pellicle helps shield the teeth against acid that can cause
caries. However, the pellicle also forms a prime surface for bacteria
and other microorganisms that lead to the development of plaque.
Plaque — Plaque is the scourge of the mouth. It 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 dead
body tissue. Plaque grows when more bacteria join in, when the bacteria
already there start to multiply, or when bacteria byproducts and food
debris accumulate. Plaque starts forming immediately after a tooth is
cleaned. It builds up to measurable levels after about one hour and
takes an average of seven days to fully mature. As it matures, more and
more different types of microorganisms appear, the plaque thickens and
gum inflammation begins. Plaque that forms on the crowns of the teeth,
the part that shows above the gums, is called supragingival plaque;
plaque under the gums is called subgingival plaque
.
Calculus — If left alone long enough, plaque begins to mineralize
and harden into calculus, also known as tartar. Calcium, phosphorus and
other minerals from saliva become incorporated into the plaque, form
crystals and harden the plaque structure. Plaque begins to mineralize
within 24 hours and it is fully hardened and transformed to calculus
within 12 to 20 days. Then, new plaque forms on top of existing calculus
and this new layer can also become calcified. For that reason, calculus
is usually found in layers.
Bacteria — We all have many different strains of bacteria in our mouths.
Some bacteria are good for us because they help control populations of
more 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 a lot of acid. Another common acid-producing
bacteria, lactobacillus, is less destructive because it can attach only
to plaque, not to the tooth itself. A third type of bacteria, actinomyces also plays a role in tooth decay. Other bacteria cause
periodontal disease and include porphyromonas gingivalis, prevotella
intermedia and bacteroides forsythus.
Dental Decay "Cavities"
If you never ate any food and brushed your teeth twice a day, the decay
process would never get started. But the minute you put food in your
mouth, the sequence begins.
In a clean mouth, the pellicle, a microscopically thin, clear coating on
the teeth formed by certain proteins in the saliva, starts forming
immediately after brushing. Soon after, microorganisms attach themselves
to the pellicle and begin to form plaque on the teeth. At this point,
mouth tissues and plaque have a pH of about 6.2 to 7.0. pH is a measure
of acidity or alkalinity on a scale of 1 1 to 14. A pH of 7 indicates a
substance is totally neutral, neither acid nor alkaline. Lower numbers
on the scale indicate a substance has more acid and higher numbers mean
the substance is more alkaline. At a normal pH of 6.2 to 7.0, the mouth
is close to neutral and no damage is being done to the teeth. If the pH
drops below 5.5, the enamel that covers the portion of the tooth above
the gums starts to demineralize, which means it loses some of the
minerals in its structure and begins to break down. Between a pH of 5.5
and 6.0, the acid can begin to destroy the roots of the teeth under the
gum line.
So how do our mouths become acidic? That's where the sugar connection
comes in. And it's not just candy and ice cream we're talking about. All
carbohydrate foods, as they are digested, eventually are broken down
into simple sugars: glucose, fructose, maltose and lactose. Some of this
digestion begins in the mouth with digestive enzymes in saliva. 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 bread, crackers, bananas, potato
chips and breakfast cereals.
The process of digestion begins in the mouth. The sugars created by that
process are used by the bacteria, which form acids as a byproduct. These
acids cause the mouth's pH to drop and begin to dissolve the mineral
crystals inside the teeth.
The longer the pH remains lower than 5.5, the more acid damage will be
done. Therefore, carbohydrate foods that tend get stuck to teeth tend to
do more acid damage. Teeth with a lot of nooks and crannies, such as
molars, are more likely to trap food and are therefore more susceptible
to caries. Plus, every time you eat a fermentable carbohydrate, the pH
of your mouth remains below 5.5 for up to several hours, depending on
the quality of your saliva. People who sip soft drinks or sweetened
coffee throughout the day or who eat many
small carbohydrate snacks will
have an acidic mouth almost constantly.
What's worse is that bacteria love sugar, and they thrive and multiply
in an acid environment. So the more sugar you eat, the more acidic your
mouth and the more bacteria will grow. The more bacteria you have, the
more acid will be produced when you eat sugar. The cycle builds on
itself, creating an ever more destructive environment for teeth.
Types And Stages Of Decay
When acids first start dissolving the tooth, a white spot appears on the
enamel. This is where the demineralization has begun to weaken the
enamel and start a cavity inside the tooth. At this stage, the tooth can
remineralize and fix the weakened area itself with the help of 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 continue.
It has been known to eat away at a tooth all the way through the enamel,
through the dentin and down to the pulp of the tooth.
In young children, teeth that have just recently emerged have weak
enamel and are highly susceptible to acid decay. Acute caries, which
destroys enamel quickly, is common in children and young adults. 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
progress or progress at a very slow rate. They will tend to be darker in
color because the edges get stained from normal eating and drinking.
lPlaque
Plaque is the scourge of the mouth. It 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 dead
body tissue. Plaque grows when more bacteria join in, when the bacteria
already there start to multiply, or when bacteria byproducts and food
debris accumulate. Plaque starts forming immediately after a tooth is
cleaned. It builds up to measurable levels after about one hour and
takes an average of seven days to fully mature. As it matures, more and
more different types of microorganisms appear, the plaque thickens and
gum inflammation begins. Plaque that forms on the crowns of the teeth,
the part that shows above the gums, is called supragingival plaque;
plaque under the gums is called subgingival plaque.
Root caries is more common in older adults than in younger adults for a
couple of reasons. Older adults are more likely to have gums that have
receded from years of hard brushing or periodontal disease. That can
higher risk of decay. Older adults also have higher incidences of dry
mouth (xerostomia), which increases the risk of decay.
Recurrent caries is decay that forms beneath fillings or other
restorations, like 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 enough to leave a gap.
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