Many different types of bacteria normally
live in the human mouth. They build up on the teeth in a sticky film called
plaque. This plaque also contains saliva, bits of food and other natural
substances. It forms most easily in certain places. These include:
• Cracks,
pits or grooves in the back teeth
• Between
teeth
• Around
dental fillings or bridgework
• Near
the gum line
Some of the plaque bacteria turn sugar and
carbohydrates (starches) in the foods we eat into acids. The acids dissolve
minerals in the hard enamel that covers the tooth's crown (the part you can
see). The enamel erodes or develops pits. They are too small to see at first.
But they get larger over time.
Acid also can seep through pores in the
enamel. This is how decay begins in the softer dentin layer, the main body of
the tooth. As the dentin breaks down, the enamel over it can collapse, forming
a cavity.
If the cavity is not fixed, bacteria will
get into the tooth's inner layer. This contains the soft pulp and sensitive
nerve fibres.
Tooth roots exposed by receding gums also
can develop decay. The root's outer layer, cementum, is not as thick as enamel.
Acids from plaque bacteria can dissolve it rapidly.
No one really knows what causes the pain
people get with cavities that have not entered the pulp.
Theories include:
• Inflammation
caused by bacteria
• Exposure
of the root surface
• Imbalance
of fluid levels in tiny openings called tubules inside the dentin
Symptoms
Early caries may not have any symptoms.
Later, when the decay has eaten through the enamel, the teeth may be sensitive
to sweet, hot or cold foods or drinks.
Diagnosis
A dentist will look for caries at each
office visit. This will be part of the exam, whether it is a routine visit or
an appointment made because of pain. The dentist will look at the teeth and may
probe them with a tool called an explorer to look for pits or areas of damage.
The problem with these methods is that they often do not catch cavities when
they are just forming. Occasionally, if too much force is used, an explorer can
puncture the enamel. This could allow the cavity-causing bacteria to spread to
healthy teeth.
Newer devices also have been developed to
detect tooth decay. They are useful in some situations, and they do not spread
decay. The one most commonly used in dental offices is a liquid dye or stain.
Your dentist brushes the nontoxic dye over your teeth, then rinses it off with
water. It rinses away cleanly from healthy areas but sticks to the decayed
areas.
Some dentists also use high-tech devices
such as lasers to detect cavities. Under many conditions, these devices can
detect very early tooth decay, which can actually be reversed.
Lastly, more advanced caries can be seen on
X-rays. They are taken on a set schedule, or to find out the cause of symptoms
such as pain.
Expected Duration
Caries may be curable, or not, depending on
when it is found. White spots may indicate early caries that has not yet eroded
through the enamel. Early caries may be reversed if acid damage is stopped and
the tooth is given a chance to repair the damage naturally.
Caries that has destroyed enamel cannot be
reversed. Most caries will continue to get worse and go deeper. With time, the
tooth may decay down to the root. How long this takes will vary from person to
person. Caries can erode to a painful level within months or years.
Prevention
One way you can prevent cavities is by
reducing the amount of plaque and bacteria in your mouth. The best way to do
this is by brushing and flossing daily. You also can use antibacterial mouth
rinses to reduce the levels of bacteria that cause cavities.
You can reduce the amount of tooth-damaging
acid in your mouth by eating sugary or starchy foods less often during the day.
Your mouth will remain acidic for several hours after eating. Therefore, you
are more likely to prevent caries if you avoid between-meal snacks.
Chewing gum that contains xylitol helps to
decrease bacterial growth. The bacteria cannot use the xylitol as a food
source, like sugar. Other products also can reduce the acid level in your
mouth. Ask your dentist about them.
Another way to reduce your risk of cavities
is through the use of fluoride, which strengthens teeth. A dentist can evaluate
your risk of caries and then suggest appropriate fluoride treatments. Fluoride
in water strengthens teeth from within, as they develop, and also on the
outside. Dentists also can paint fluoride varnish on children's primary teeth
to protect them from decay.
In adults, molars can be protected with
sealants. In children, both baby molars and permanent molars can be sealed.
Dentists also can use sealants on molars that have early signs of tooth decay,
as long as the decay has not broken through the enamel.
Treatment
Caries is a process. In its early stages,
tooth decay can be stopped. It can even be reversed. Fluorides and other
prevention methods also help a tooth in early stages of decay to repair itself
(remineralize). White spots are the last stage of early caries.
Once caries gets worse and there is a break
in the enamel, only the dentist can repair the tooth. Then the standard
treatment for a cavity is to fill the tooth. If a drill is used, the dentist
will numb the area. If a laser is used, a numbing shot is not usually required.
The decayed material in the cavity is removed and the cavity is filled.
Many fillings are made of dental amalgam or
composite resin. Amalgam is a silver-gray material made from silver, mercury,
copper or other metals. Composite resin offers a better appearance because it
is tooth-colored. Newer resins are very durable.
Amalgams are used in molars and premolars
because the metal is not seen in the back of the mouth. Composite and ceramic
materials are used for all teeth.
If a cavity is large, the remaining tooth
may not be able to support enough filling material to repair it. In this case,
the dentist will remove the decay and cover the tooth with a ceramic inlay,
onlay or artificial crown. These may be made in the office or in a lab.
Sometimes the part of the tooth you can see
remains relatively intact, but there is decay in the pulp inside the tooth. In
this case, the tooth will need root canal treatment. A general dentist or an
endodontist will be able to remove the tooth's pulp and replace it with an
inert material. In most cases, the tooth will need a crown.
When to Call a Professional
The early stages of decay are usually
painless. Only regular professional examinations and X-rays can detect early
trouble. If you develop sensitivity to chewing or to hot, cold or sweet foods
or drinks, contact your dentist.
Prognosis
If caries is not treated, it likely will
cause the tooth to decay significantly. Eventually, uncontrolled decay may
destroy the tooth.
Having caries increases your risk of more caries
for several reasons:
• Caries
is caused by bacteria. The more decay you have, the more bacteria exist in your
mouth.
• The
same oral care and dietary habits that led to the decay of your teeth will
cause more decay.
• Bacteria
tend to stick to fillings and other restorations more than to smooth teeth, so
those areas will be more likely to have new caries.
• Cracks
or gaps in the fillings may allow bacteria and food to enter the tooth, leading
to decay from beneath the filling.
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