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Osteonecrosis of the jawbone
(ONJ) is a disease
resulting from the temporary or permanent loss of the blood supply
to the bone. Without a blood supply, the bone dies (the term
"osteo" means "bone"; the term "necrosis" means "death").
When this happens, the dead bone becomes exposed to the oral
environment. Exposed necrotic bone is not an uncommon
complication after extractions of teeth, even in healthy patients
who have never had radiation therapy or bisphphonate drug therapy.
Simple cases involve only the bone immediately surrounding the
extraction socket, and usually, the necrotic bone will heal over
spontaneously with time.
Serious
ONJ is extremely rare in dentistry, and it tends
to happen only to patients who have known predisposing factors such
as radiation therapy for cancers of the head and neck or
IV bisphosphonate drug therapy for metastasizing cancers or
osteoporosis. Osteonecrosis of the jaw generally happens
in susceptible patients after a dental extraction or periodontal
osseous surgery. It may also happen after a fall or an auto
accident in which the jawbone is broken. It can even happen
under an ill fitting denture. The presence of exposed necrotic bone in the oral
cavity may cause the patient pain, but surprisingly, it is often
asymptomatic, possibly because the necrotic bone acts like
a dressing over the vital bone and allows healing to take place
underneath it.
There is no specific treatment for osteonecrosis
of the jaw other than treatments aimed at preventing infection and
controlling pain if present. More advanced cases may
require conservative debridement of necrotic bone. Many cases
of osteonecrosis will heal over time. Some (very few) never heal.
Other terms for osteonecrosis are
avascular necrosis, aseptic necrosis and ischemic bone necrosis. There are two named types of
osteonecrosis in dentistry: Osteoradio-necrosis (radiation associated
bone death), and Bisphosphonate Related OsteoNecrosis of the Jaw
(BRONJ).
Osteoradio-necrosis is the name given to necrosis of
a portion of the jawbone in a patient who has
received extensive radiation therapy for the treatment of
cancers in the head and neck. Radiation affects rapidly
growing cells, and the cells in the endothelial lining of blood vessels
are especially vulnerable to damage from large amounts of
radiation. High doses of radiation result in a cumulative
progressive endarteritis (inflammation of the inner lining of
the arteries) which eventually leads to the destruction of the
smaller arteries in the bone. Dense bone, like that found
in the lower jaw is not especially well vascularized to begin
with, and therapeutic amounts of radiation (far in excess of the
radiation used to take normal diagnostic dental x-rays) reduces
the blood flow further making normal healing of the bone
difficult.
Patients who have had extensive cancer
related radiation therapy to their head or neck should be
sure to tell their dentist about this and avoid having teeth
extracted. This often means doing root canals on teeth
that are otherwise hopelessly decayed and non restorable.
Patients who have had this type of radiation therapy should
be especially careful to avoid excessive sugar intake and be
meticulous about their oral hygiene.
Osteoradio-necrosis is NOT associated with
diagnostic x-rays like the ones your dentist takes
periodically to examine your teeth.
Bisphosphonate Related Osteonecrosis of the
Jaw (BRONJ)
Bisphosphonates are therapeutic agents used to
treat diseases that feature bone fragility. These diseases
include osteoporosis, Paget's disease of bone, multiple myeloma
and certain cancers in which metastases are a feature,
especially breast cancer. Bisphosphonates inhibit
osteoclast activity thus inhibiting the resorption of bone.
This will make
the bone more dense, but also less vascularized and less able to
remodel after injuries.
Necrotic bone exposed to the oral environment for at
least eight weeks in a patient that has been treated with any of the
bisphosphonates is called Bisphosphonate Related OsteoNecrosis of
the Jaw, or BRONJ for short. Some authorities refer to it as
BON which stands for Bisphosphonate OsteoNecrosis. BRONJ can be a complication after
extractions, periodontal surgery involving bone recontouring
or facial trauma from any source. It can also occur
spontaneously in susceptible patients. BRONJ can occur in the upper
or lower jaw, however the
incidence in the lower jaw is twice as high as in the upper.
BRONJ may also follow less traumatic injuries such as chronic
denture sores.
There is no specific treatment for
Bisphosphonate Related OsteoNecrosis of the Jaw other than treatments aimed at preventing infection and
controlling pain if present. More advanced cases may
require conservative debridement of necrotic bone. I am unable to find any
reference to patients actually dying as a direct result of
BRONJ, although patients being treated with IV bisphosphonates
for metastasizing cancers or multiple myeloma may die of an
accumulation of the side effects of their treatment modalities which
may include very serious BRONJ. In patients taking low doses
of oral bisphosphonates for osteoporosis (such as Actonel,
Boniva, or Fosamax), spontaneous healing is actually quite a
frequent occurrence.
Oral bisphosphonates
Most people are familiar with the names of
several of the oral drugs used to treat
osteoporosis, since the companies that manufacture them do a
lot of advertising.
| Brand Name |
Manufacturer |
Generic Name |
| Actonel |
Procter & Gamble Pharmaceuticals
|
risedronate |
| Boniva |
Roche Laboratories |
ibandronate |
| Fosamax |
Merck & Co. |
alendronate |
| Fosamax Plus D |
Merck & Co. |
alendronate |
| Skelid |
Sanofi Pharmaceuticals |
tiludronate |
| Didronel |
Procter & Gamble Pharmaceuticals
|
etidronate |
Patients taking oral
bisphosphonates such as the ones listed above, have a
very low risk of developing BRONJ. These
patients seem to have less severe manifestations of necrosis
which respond more readily to
stage specific treatment regimens.
Dentists should inform patients that they have a small chance of
contracting osteonecrosis, however
dentoalveolar surgery does not
appear to be contraindicated in this group. The
actual incidence of BRONJ in the total population of
patients who take oral bisphosphonates is approximately 0.7
cases per 100,000 patients per year. The risk of BRONJ
is especially low if the patient has been taking the
bisphosphonate for less than three years and has no other
complicating factors. These complicating factors
include:
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Diabetes
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Concurrent steroid use
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Smoking
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Poor oral hygiene, especially in
patients with periodontal disease
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Therapeutic head and neck radiation
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The concurrent administration of
other chemotherapeutic agents.
Question: Does the risk for BRONJ
decrease if the patient stops taking the oral bisphosphonate
for several months before having their extraction?
Answer: There is no hard data proving
that there is a benefit to halting oral bisphosphonate
medication, even for several months prior to the surgical
procedure. Evidence suggests that the drug remains in
the bony structure more or less permanently. The half
life of bisphosphonates in bone is about 10 years.
Even so, drug holidays are still recommended for patients
who have been taking their drug for over three years.
The rule of thumb seems to be that no delay
in surgery is necessary for patients who have been taking
oral bisphosphonates for less than three years unless
they have one or more of the above complicating factors.
If the patient has been taking bisphosphonates for more than
three years or has complicating factors, a three month drug
holiday is advised prior to surgery with the holiday
extending until bony healing is complete (usually about
three months post-op). Click
here for the reference.
Question: Does the length of time a
patient has been taking an oral bisphosphonate affect the
probability that the patient will contract BRONJ?
Answer: Yes! The general
consensus is that the probability of contracting
bisphosphonate related osteonecrosis of the jaw as a result
of dental osseous surgeries during the
first three years of oral drug therapy is substantially less than
for those patients who have been taking the drug for more
than three years. Patients and dentists should strive
to produce a state of oral health during the first
three years of bisphosphonate therapy to reduce the
likelihood of BRONJ later.
Question: Is a patient taking
oral bisphosphonates likely to develop BRONJ after implant
placement?
Answer: Implants have been known to
fail in patients taking oral bisphosphonates. However
studies of patients on oral bisphosphonates receiving
implants indicate a very low risk of either implant loss or
BRONJ following implant placement, especially if the patient
has been taking the drug for less than three years.
IV bisphosphonates
While patients taking oral bisphosphonates
show a very low risk of BRONJ, patients taking IV
(injection) bisphosphonates are at significant risk of
developing BRONJ after extractions or other surgical
interventions involving the manipulation of bone
(incidence is 0.8-12%). IV bisphosphonates are
generally used as part of a chemotherapeutic regimen for the
treatment of cancer. The most commonly used IV
bisphosphonates are:
| Brand Name |
Manufacturer |
Generic Name |
| Aredia |
Novartis |
pamidronate |
| Zometa |
Novartis |
zolendronic acid |
| Bonefos |
Schering AG |
clodronate |
Any patient who has been treated with IV
bisphosphonates should follow these guidelines:
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Avoid extractions unless the teeth
are very mobile.
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Choose root canals rather than
extractions whenever possible.
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Have extremely good oral hygiene and
regular dental care.
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Be especially careful to keep your
dentures in good repair to avoid chronic sore spots.
Patients are advised to have relines every 2 years
and get new dentures every five to seven years.
(Click
here to see why.)
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Before the prescription of bisphosphonates
for bone disease the patient should be made dentally fit so
that the need for subsequent dental extractions is
minimized.
Staging and treatment for ONJ patients Click
here for the reference.
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Stage 1: Exposed/necrotic bone in
patients who are asymptomatic and have no evidence of infection.
-
Stage 2: Exposed/necrotic bone in
patients with pain and clinical evidence of infection.
-
Stage 3: Exposed/necrotic bone in
patients with pain, infection, and one or more of the following:
pathologic fracture, extra-oral fistula, or osteolysis extending
to the inferior border.
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