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 Understanding Impacted Wisdom Teeth & The
Reasons for Extracting Wisdom Teeth
These are the facts about wisdom teeth how they develop, how
they become impacted, and why they are often removed. This
information sheet aims to explain why some people have impacted
wisdom teeth and why some don't.
About your teeth
The adult mouth has up to 32 permanent teeth: 16 in each jaw.
When you look in the mouth, you see only part of each tooth, the
crown. The other part of the tooth, the root, lies underneath the
gums, embedded in the jawbone. Most teeth have one root. The back
teeth, called molars, have two or three roots. These extra roots
mean more support and a greater ability to handle the pressures of
chewing. What we call "wisdom teeth" are actually third molars. You
also have first molars and second molars. There are usually four
wisdom teeth (but some people naturally have fewer), one upper and
one lower on each side of the mouth. They develop inside the bones
of the jaws, as do all the teeth, but are the very last teeth to
come in. They lie in the very back of the mouth.
Wisdom teeth begin to form at about age 9. They form in a small
hollow that develops inside the upper and lower jawbones. The
crowns develop first and are usually completed by age 14. By the
late teen years, when the roots have almost finished forming, the
wisdom teeth usually erupt (move through the bone) into the
mouth.
Sometimes, wisdom teeth cannot erupt at all. As the roots of the
wisdom teeth develop, the teeth begin to move slowly through the
bone and only the crown portion comes into the mouth. The-root
portion stays firmly anchored in the bone. By 16 years old, the
jaws have almost reached their adult size. Some jaws eventually
grow long enough to allow room for the wisdom teeth some do
not.
Once the crowns have fully erupted, the wisdom teeth can be used
for chewing.
It is important to appreciate that the wisdom teeth have moved from
inside the bone (where they were developing) to a position partly
inside the bone (the roots) and partly outside the bone (the
crowns) of the jaw. Although the crowns are fully erupted, the root
tips must still finish forming over the next few months. It is
untrue that all wisdom teeth must be extracted.
But what happens when there is not enough space for the wisdom
teeth? The teeth remain trapped inside the bone and are said to be
impacted. To be considered not impacted, practically all of the
crown would have to be free of bone and gum. Impacted teeth can
take many positions inside the bone. Their roots might occasionally
be curved and twisted.
Sometimes the jaws are too short to allow room for the wisdom
teeth to come in. As they try to erupt, the upper and lower wisdom
teeth have come up against the backs of the second molars and can
go no farther. They are trapped inside the bone.
This situation can make removal a longer and more challenging
procedure for the surgeon and can make healing a slower
process.
During a routine dental examination, the dentist takes X-rays
(radiographs). X-rays will reveal
impacted wisdom teeth, showing their position and what is happening
around them. Are they pushing up against the second molars? Is
there infection nearby? By reviewing the X-rays, the dentist can
tell if wisdom teeth will erupt normally or become impacted.
Wisdom teeth can cause problems:
Gum infection
Infection of the gum around an impacted wisdom tooth is common.
The back teeth are the hardest to clean, so it is easy for food
debris and bacteria to work their way down behind the second
molar.
Then an infection starts around the crown of the impacted wisdom
tooth. The gum may swell up, and there may be a great deal of pain.
People often mistake repeated soreness of the gum over a Wisdom
tooth as an effort by the tooth to erupt. Rather, it may be a
warning that there is trouble brewing. If a gum infection goes
untreated, it may extend into the jaw. Deep bone infection can
sometimes progress for years, unknown to the patient. Infection can
(albeit rarely) break through the bone into the cheek or neck. Most
of the time a chronic infection could be thought of more as a
residence of stale bacteria that produces bone and tissue degrading
byproducts (compared to an acute infection with draining
purulence/pus). Swelling of the face, high fever, difficulty
opening the mouth, or difficulty with swallowing may indicate an
acute infection due to an impacted wisdom tooth.
Damage to other teeth
An impacted wisdom tooth can put constant pressure on the back
of the second molar it presses
against. Over time, this pressure may be enough to destroy the back
of the other tooth, usually in the form of an erosive cavity. You
may not feel a thing until it is too late; the tooth may be
unrestorable or require great effort to fix.
Caries (Cavities)
As wisdom teeth are very difficult to keep clean they are prone
to cavities and this can lead to a tooth that is grossly decayed
and is no longer functional.
Periodontal (gum disease) Considerations
Wisdom teeth can cause adjacent teeth to become periodontally
(gum-disease) involved. With repeated infections and possible
trapping of plaque, food or decay between the wisdom tooth and its
neighbours. The bone support of the adjacent tooth can be eroded
away and then the future of that tooth can be put in jeopardy.
Cyst formation
A thin sac lines the hollow in which the wisdom tooth originally
develops inside the bone. In normal eruption, this sac disappears.
But, if the tooth is impacted, the sac remains and can fill up with
fluid from the surrounding bone. The sac becomes a cyst, which is
an abnormal sac of fluid. A cyst destroys bone as it grows.
Pain
An impacted wisdom tooth can cause neuralgia-like pain. In the
nature of referred pathways, shooting, aching pain can spread out
to other areas of the head and neck.
Temporary numbness
A nerve in a canal on each side of the lower jaw carries feeling
from the skin of the lip and chin. In some people the roots of a
fully formed wisdom tooth lie close to this canal. After the tooth
is
removed, they may experience a feeling of temporary numbness in the
lip and chin.
This numbness is generally not serious since the lip moves quite
normally (the nerves to the muscles that move the lips are not
affected), but itcan be an annoyance. Rarely, a small spot of
numbness may last for years. But in most cases it usually takes a
few weeks for the last bit of numbness to completely disappear.
If wisdom tooth roots have not yet completely formed, they are
usually too short to be close to the canal. Then the chance of any
numbness happening is most unlikely. The timing of wisdom tooth
extraction varies, they are usually removed between the late teens
and the age of thirty when the jawbones are more elastic and you
are able to heal more quickly when you are young. But, if a wisdom
tooth is diseased and is compromising your health then it can be
removed at any time. Your dentist will discuss the reasons for your
wisdom teeth extraction with you at length. If you have any
questions do not hesitate to ask. | 