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What is osteonecrosis?
- A rather frightening word which is hard to explain
in simple terms
- A previously rare jaw problem now being observed in
a small percentage of myeloma patients taking Aredia and Zometa
- A condition in which there is pain, swelling and
bone damage around the tooth sockets in the jaws. There is bone necrosis or loss
of bone which can lead to loose teeth, sharp edges of exposed bone or bone
spurs, breaking loose of small bone spicules or dead bone.
- A patient may notice nothing initially, or may start
to experience pain, swelling, numbness or a “heavy jaw feeling” or loosening of
a tooth.
What Are Bisphosphonates
Bisphosphonates, analogs of a naturally occurring compound,
pyrophosphate, that serves to regulate calcium, are drugs that prevent bone
breakdown.
A
History
Bisphosphonates have been known to chemists since the middle of
the 19th century. The early uses of bisphosphonates were industrial,
mainly for corrosion prevention, and largely used in the textile, fertilizer and
oil industries as well as in washing powders.
The study and development of bisphosphonates as a major class
of drugs for the treatment of bone diseases began only three decades ago. The
first report of the biological characteristics of bisphosphonates was published
in 1968. At that time, scientists discovered that bisphosphonates have a marked
ability to inhibit bone resorption.
Bone Structure and
Development
The two primary bone cells are the osteoclasts and the
osteoblasts. The osteoclasts are the cells that resorb, or break down, bone and
the osteoblasts are the cells that build up bone.
Bone is built during fetal life, youth and adolescence. Once
bones are formed, their shape and structure are continually renovated and
modified by two processes known as modeling and remodeling. Both modeling and
remodeling result in the replacement of old bone by new bone.
Modeling and remodeling begin with bone being eroded by
osteoclasts, which is then followed by osteoblasts refilling the resorption
sites. It is necessary for bone resorption to occur in order to trigger bone
formation.
Modeling takes place during an individual's growth and is the
main process through which the skeleton increases its volume and mass. In
modeling, new bone is formed at a different location than where the bone was
broken down. This results in a change in the shape of the skeleton and also is
the cause for the increase in bone size.
The remodeling process occurs in adults. In remodeling, the
growth that increases bone shape and size is modified so that the newly formed
bone replaces the broken down bone at the same site. Therefore, no change occurs
in the shape of the bone.
Normally, the amount of bone formed during bone remodeling
equals the amount of bone destroyed. When more bone is destroyed than formed,
however, a bone loss occurs and bone diseases, such as osteoporosis, may
develop. In some instances, such as Paget's disease of bone and osteopetrosis,
more bone is produced than is broken down, and this bone is architecturally
unsound.
How Bisphosphonates
Work
Bisphosphonates are drugs that suppress or reduce bone
resorption by osteoclasts. They do this both directly, by hindering the
recruitment and function of osteoclasts (the bone-resorbing cells) and perhaps
indirectly, by stimulating osteoblasts (the bone-forming cells) to produce an
inhibitor of osteoclast formation. There is now a reasonable understanding of
how these drugs work and the differences between the various types of
bisphosphonates are better understood.
Though bisphosphonates suppress the abnormal bone resorption
associated with Paget's disease of bone, fibrous dysplasia and metastatic cancer
to bone, they do not cure the diseases. Bisphosphonates are particularly
effective in relieving pain in these diseases, however. There is no evidence
that bisphosphonates interfere with the healing of fractures.
Bisphosphonates Osteonecrosis Links
NEJM -- Osteonecrosis of the Jaw and Bisphosphonates 
Correspondence from The New England Journal of Medicine -- Osteonecrosis of the Jaw and Bisphosphonates ... To the Editor: Cases of osteonecrosis of the jaw in connection with the use of ... reports concerning the possible association between bisphosphonates and osteonecrosis of the jaw
Correspondence from The New England Journal of Medicine -- Osteonecrosis of the Jaw and Bisphosphonates ... To the Editor: Cases of osteonecrosis of the jaw in connection with the use of ... reports concerning the possible association between bisphosphonates and osteonecrosis of the jaw
... Bisphosphonates. etidronate (Didronel), pamidronate (Aredia), alendronate (Fosamax), risedronate (Actonel ... The bisphosphonates are very powerful, they cause dramatic changes ...
(Medical Journal of Australia) Bisphosphonates and osteonecrosis of the jaw ... <PubMed> Schwartz HC. Osteonecrosis and bisphosphonates: correlation versus caution ... Greenberg MS. Intravenous bisphosphonates and osteonecrosis. Oral Surg Oral Med Oral Pathol Oral ...
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