Periapical lesions – causes, symptoms, diagnosis, treatment, pathology


Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
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much more. Try it free today! Bacterial infections of the tooth and the
surrounding tissues progress rather slowly, but every step is so much more severe than
the previous one. Cariogenic bacteria will first tear enamel
down. Then they’ll bore through dentin. When they or their toxic waste get into the
pulp, pulpitis occurs. Without immediate treatment, pulpitis can
cause irreversible damage and require a root canal. If no treatment is performed, the pulp will
eventually die off through necrosis. At that point, the tooth is considered dead,
and in essence, it becomes a staging area for bacteria to spread further. Our immune system will, at that point, try
to stage a defense around the apices of the dental root. We call that “battlefield” apical periodontitis,
which is one of the periapical lesions. The primary form of defense our body has against
infection is the polymorphonuclear leukocyte, also known as the neutrophil. It is the finest soldier serving our body,
and its task is to locate and destroy microbes that intrude into the body, wherever that
might be. This is usually a very effective force, and
most of the times sufficient. When an infection occurs, neutrophils will
mobilize in huge numbers, head to the site of infection, and leave the circulatory system,
searching for bacteria to destroy. They achieve this through three methods. First is degranulation, where neutrophils
release a bunch of granules containing various enzymes, that hurt bacteria. Then, they will use neutrophil extracellular
traps, or NETs, to immobilize the wounded bacteria. These are actually nets, made out of neutrophil
DNA! Finally, neutrophils will then gobble up the
bacteria through phagocytosis as a final means of its destruction. All of this works really well, most of the
time. But, fighting infection is a bloody affair
and many of the neutrophils perish during the fight. Macroscopically, the battlefield, containing
neutrophil remains, released enzymes, NETs and dead bacteria, makes up pus. And a lot of it can accumulate, given the
severity of the infection. Enzymes from the pus will irritate the surrounding
tissues, creating an acute phase of apical periodontitis. The accumulation of pus is called a periapical
abscess, as it surrounds the root. This abscess can eventually form a sinus tract,
which is a narrow passageway that extends from the abscess to the mouth, through which
the pus can drain out. The periapical abscess can also progress into
a periapical cyst, which is when fibrous tissue and immune cells surround an area of chronic
infection containing pus. In less fortunate cases of periapical lesions
on the maxillary teeth, the cyst can form a fistula to the maxillary sinus, causing
a severe case of sinusitis. If the external drainage fails to happen,
and the cyst or abscess continues to grow, the lesion might progress to osteomyelitis,
which is the inflammation of the underlying bone, or cellulitis, which is the inflammation
of the throat. One severe form of cellulitis is called Ludwig’s
angina, where the inflammation of soft tissues is so severe, it may lead to death through
suffocation. Treatment of periapical lesions usually involves
antibiotics to curb the infection. Then, an endodontic therapy is performed where
the decaying pulp is removed and the abscess is drained. The pulp space gets thoroughly cleaned and
disinfected, while the tooth crown is repaired, allowing the dead tooth to continue doing
its mechanical function of chewing. Endodontic therapy has a high success rate,
however, the treated tooth can sometimes reinfect and an extraction may be required. All right, as a quick recap. Periapical lesions are inflammatory in origin,
and involve apical periodontitis, which may evolve into periapical abscess or a periapical
cyst. Abscesses can drain into the mouth or cause
cellulitis. Treatment involves antibiotics, pus drainage,
endodontic treatment of the tooth, and failing all that, extraction of the affected tooth.

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