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Everyone who has ever had a pimple has had an abscess, even though they're tiny, they're
still abscesses.
An abscess forms when normal tissue, like the gingiva or gums and teeth for example,
is split apart and that new space is invaded by nearby pathogens like bacteria.
In a healthy mouth, normal or commensal bacteria thrive but don't cause disease.
However, any cut or break in the mucosa is an invitation for bacteria to dive in and
multiply, causing an infection.
When that happens, the immune system typically responds and a battle ensues with the result
being pus - a mixture of bacteria, immune cells, and dead tissue.
So, in response to an injury, cells release small chemicals called cytokines, like tumor
necrosis factor, interleukin-1, interleukin-6, interleukin-8, and interleukin-17, and these
attract nearby immune cells.
It's kinda like like yelling for help and being heard by the nearby police.
In addition, the cytokines also dilate nearby capillaries and make them leaky - which brings
more blood to the site, and allows immune cells that do show up, to easily slip out
of the blood and into the tissue.
The first immune cells at the scene are neutrophils, and they release chemicals and enzymes that
kill themselves and the bacteria they swallow up, creating a pool of dead bacteria and cells.
This is a specific type of acute inflammatory response called suppurative inflammation,
which simply means that pus is created in the process.
From a macroscopic view, this is sometimes referred to a liquefactive necrosis, because
the area of dead tissue turns to liquid.
Initially the dead tissue is intermixed with healthy tissue, but over time it can coalesce
into a single area.
And around this pool of pus, a wall of fibrinogen - starts to harden into a barrier.
Occasionally sheets of fibrin form septations, creating loculations or pockets of pus within
the abscess itself...kinda like an abscess within an abscess...
Even though the pus is largely dead material, there are still plenty of live bacteria within
the pus, which makes it highly infectious if it gets spread from one place to another.
There are a few different types of dental abscesses.
The first one is called a periapical abscess, and it's located at the apical foramen of
the tooth.
A periapical abscess begins when bacteria gain entry into the dental pulp of the tooth
through an opening caused by dental caries or from trauma.
The inflammation then spreads and causes necrosis or tissue death throughout the entire length
of the dental pulp.
And if it goes on without treatment - like a root canal, then the infection ultimately
reaches the apical foramen of the tooth.
Subsequently, the infection reaches the periapical tissues and at that point, it's considered
apical periodontitis, which is inflammation of the periapical tissues which secure the
tooth in its socket.
The infection usually develops into an abscess as the pus coalesces, and it can involve nearby
structures like the alveolar bone and adjacent teeth.
Sometimes periapical abscesses become quiescent, meaning that they don't grow much but the
bacteria remain alive within the abscess cavity.
In that situation, it's called chronic inflammation, and it's where a periapical granuloma forms
from this walled-off area.
In fact, technically, the term "granuloma" is a misnomer in this case since these lesions
don't look like normal granulomas under a microscope.
During this stage where there's a stalemate between the infection and the immune system,
if the infection gains the upper hand, then it's called an acute apical abscess.
Another type of dental abscess is a periodontal abscess, and that involves both the periodontal
structures and the gingiva.
Typically, a periodontal abscess occurs when there's a pre existing periodontal pocket,
perhaps from a deep plaque collection or from a medical procedure.
Bacteria get into the periodontal pocket, and multiply, leading to an infection and
an abscess.
Next, there's the gingival abscess, which is where the abscess only involves the gingiva
next to the bone, called the marginal or interdental gingiva, while sparing the periodontal structures.
This usually occurs when food, plaque, or another foreign object gets stuck in the gingival
sulcus, providing a protected place for bacterial growth.
Finally, there's a pericoronal abscess.
This occurs when a tooth does not erupt completely, leaving a flap of gingival tissue over the
top of the crown.
When food or another foreign object gets deeply trapped between the flap of gingival tissue
and the top of the tooth, an abscess can form.
Generally speaking, dental abscesses contain a mix of different bacteria.
Some are facultative anaerobes, which means that the bacteria prefer to make energy using
oxygen but can also survive without oxygen, like Streptococcus anginosis group and the
viridans group of Streptococci.
Others are obligate anaerobes, which means that the bacteria thrive only in the absence
of oxygen, like Fusobacterium and Prevotella groups.
Symptoms of dental abscesses mainly include local pain and swelling, as well as generalized
symptoms like fever and malaise.
Dental abscesses can cause affected teeth to loosen and they can sometimes create a
fistula to the surface, where the tissue overlying the abscess breaks down, allowing it to drain
out by itself.
This can either be within the mouth, or out through another surface like the cheek.
The abscesses can also erode into nearby structures such as the nasal sinuses - causing sinusitis,
the floor of the mouth, or even into the neck.
Diagnosing a dental abscess is usually done by feeling for areas of tenderness and fluctuance,
and imaging studies like x-rays or a CT scan can be done to determine the exact location
and size.
Generally speaking, infections are treated with antibiotics, but in order for antibiotics
to work, they need to first reach the bacteria, and that's usually done through the bloodstream.
Since abscesses do not have blood vessels inside of them, the antibiotics can only diffuse
into an abscess and that's not very effective especially when dealing with a large abscess;
you could imagine it getting to bacteria close to the edges, but there's no way it's
getting to the bacteria in the middle.
That's why the most important treatment for an abscess is incision and drainage - in
other words, cutting it open and removing the pus.
This is typically followed by frequent saltwater rinses, pain relieving medications, and regular
check-ups.
For periapical abscess, a root canal treatment or extraction has to be performed on the offending
tooth to get rid of the infection that cannot be reached by an incision and drainage or
antibiotic treatment.
Sometimes, antibiotics are used even after drainage to make sure that there are no additional
bacteria lingering around.
All right, as a quick recap...
Dental abscesses are a mix of immune cells, pathogens such as bacteria like viridans group
Streptococcus, and dead tissue.
Common types include periapical, periodontal, gingival, and pericoronal abscesses.
Because there's no blood supply to the middle of an abscess to deliver antibiotics, it usually
needs to be cut open so that the pus can drain out.
For periapical abscess, a root canal treatment or extraction has to be performed on the offending
tooth.
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