Who Is Affected and Where?
Maxillofacial osteonecrosis (MFO) has been microscopically
confirmed in patients as young as 12 years of age and as old
as 94, and has been reported in both genders. Typically,
however, more than 80% of patients are 35-55 years of age
and an equal proportion are women. The wisdom tooth sites,
top or bottom, are the most often involved sites (almost
half of all cases), perhaps because these have the blood
vessels furthest "from the heart," i.e. the ends of the
longest blood vessels to the tooth-bearing regions and the
place where the pressures are less and the flow is somewhat
irregular -- both conditions favor the formation of clots.
Virtually any part of the jaw, however, can be involved,
usually the tooth bearing bones but sometimes the jaw joint
(temporomandibular joint) or the flat portion of bone in the
back of the lower jaw, just in front of the ears (ramus of
the mandible).
One-third of NICO patients have more than one quadrant of
the jaws involved, not necessarily at the same time, and 10%
have lesions in all four quadrants. In our experience, the
more generalized the condition, the more likely the jawbone
patient is to suffer from multiple risk factors, including
hypercoagulation disorders.
Most MFO sites are old extraction sites, but many are found
in the marrow around a root canal treated tooth, not at the
ends of the roots where the endodontist does his or her
surgery (apicoectomy). In other words, a biopsy taken from
the usual site, i.e. the ends of the roots, will not show
the diseased marrow, only the dental infection.
The reason so many root canal treated teeth are near MFO
sites is open to debate. Some dentists believe that the
treatment itself is the cause, because endodontically
treated teeth always leave a certain number of bacteria in
the root canal or because the body reacts to the foreign
materials used to fill the treated root canal. Moreover,
studies have shown that a large proportion of endodontically
treated teeth are not done in a technically acceptable
manner. These are, in fact, features not disputed by the
endodontists themselves, although they naturally assume that
a well-performed root canal procedure cleans out enough
bacterial from the root canal and provides a good enough
seal at the end of the root that the body's own immune
system can take care of the residual bacteria which might
make it out of the canal. Likewise, the materials used have
usually been declared biocompatible, although this is such a
difficult area of research that it is almost impossible to
say that anything is completely biocompatible if left in the
body over long periods of time.
Blaming root canal treated teeth does not explain why the
majority of MFO cases occur in the wisdom tooth areas, as
these teeth are seldom treated endodontically. But the
infection and the minor surgical trauma of the root canal
treatment most certainly create a mild inflammation (the
body's response to infection and trauma) in the bone and
marrow near the diseased tooth. Inflammation releases
several chemicals capable of increasing local blood
clotting. It is designed to do this and this phenomenon is
beneficial under normal circumstances, but for a person who
already has a compromised marrow blood flow, and especially
one who tends to clot excessively because of an inherited
clotting disorder, the minor increase in local clotting can
be disastrous, leading to painful infarction and marrow
death. This phenomenon is made worse, of course, by the use
of vasoconstrictors in the numbing agents or local
anesthetics used during root canal treatment. Many NICO
patients first began experiencing their intense pain shortly
after root canal treatment, and it continues or is made
worst by extraction of the offending tooth. But many also
begin their pain saga with routine dental treatment, where
nothing is done in or near the bone and the only logical
explanation for reduced blood flow/infarction is the
anesthetic.