It has recently been found that a class of drugs called bisphosphonates has been responsible for areas of bone death or necrosis in the (mainly lower) jaw bones. These drugs are prescribed for the treatment of some cancers and osteoporosis. Aredia and Zometa are administered intravenously and are used to treat breast and prostate cancer as well as for the treatment of multiple myeloma. Oral bisphosphonates like Didronel, Actonel, Skelid, and Fosamax, are used in the treatment of osteoporosis.
ONJ vs. BON
In the articles I have been studying, two distinct and yet similar terms are being used. The first is osteonecrosis of the jaws (ONJ), which is a general term meaning “dead bone” in the jaws. The cause of this generic “dead bone” is usually trauma or long-term infection. The second term is Bisphosphonate-Associated Osteonecrosis (BON), which is a more specific term that indicates the “dead bone” was caused by Bisphosphonates.
Bisphosphonates
Bisphosphonates are powerful drugs that inhibit the normal activity of osteoclasts, which are a specific type of bone cell responsible for the removal of bone tissue. Look upon the osteoclast as a little Pac Man that goes through the bone eating up little channels. Another type of bone cell, an Osteoblast, deposits new bone. These two cells work in tandem to constantly renew the body’s bone tissue. This way, the little micro fractures that normally occur in our bones and the major fractures that occur as a result of an accident are repaired. When bisphosphonates are deposited in the bone, the osteoclasts are poisoned and they are unable to remove bone, and normal bone deposition and remodeling are severely compromised. On the good side, these drugs help kill tumors, making them important in cancer therapy.
When bisphosphonates are taken orally for osteoporosis, bone mineral loss is lessened and bone density increases. When taking lower doses of the drug, usually Fosamax, osteoclastic activity is restricted less severely. So, these patients are less likely to experience BON.
Dead Bone in the Mouth
The main deleterious side effect of these drugs is exposure of dead bone in the mouth, due to the loss of gum tissue over dead bone. This occurs mainly in the lower jaw behind the last teeth. These lesions are painful and very slow to heal. They are much more common with those patients taking the IV forms of this drug for cancer therapy. In one study, only 2.5% of the patients who experienced BON were those taking the oral form of the medication for osteoporosis.. The reason that the lesions appear in the mouth is due to the fact that jaws are subjected to constant stress from chewing and clenching. The microfractures and microdamage cannot be rapidly or adequately repaired, setting the stage for the bone to die. Additionally, the jaws have a greater blood supply than other bones and a higher metabolic rate due to the constant stress and the forces applied to the bone with the function of teeth in chewing, clenching, and grinding.
Of those patients with BON, the most common dentally associated condition was periodontitus (gum disease). In approximately one third of the cases, dental decay was associated with exposed bone. There were also associations with abscesses and failed root canals. Of the affected BON patients without dental disease, the areas most likely to be associated with spontaneous exposure of bone were areas of enlarged bony growths under the tongue called Mandibular Tori. Another common precipitating event of BON is a dental extraction.
Treatment of BON
Since treatment of this condition has not been proven successful, preventive measures become critically important. A complete dental examination prior to the initiation of bisphosphonate therapy is important. If you have already started therapy, an examination as soon as possible is recommended. There seems to be a low incidence of BON occurring less than 6 months after bisphosphonate therapy has begun. The main goal of dental treatment is the elimination of all potential sites of infection and inflammation, both dental decay and gum disease, in order to maximize your oral and overall health.
It is suggested that all patients receive a full mouth set of x-rays as well as panoramic x-ray, to check for dental disease and to detect diseases of the bone. Treatment of gum disease is important to reduce inflammation and infection. Teeth that need to be extracted should be removed as early in therapy as possible.
Restorative dentistry should be performed to eliminate decay and defective restorations (fillings and crowns) that have a high potential to promote decay. Cleaning frequency should be determined on an individual basis. Dentures and partial should be relined more frequently for a better fit so that areas of irritation to the bone are avoided.
BON and Osteoporosis Medication
At this time, it appears that the incidence of BON in Fosamax for osteoporosis is low. However, since a small percentage of the patients will get BON, and it is a very difficult condition to treat, the prudent and safe thing to do is to assume that if you are taking oral medications such as Fosamax, that you will be one of the victims of BON. Therefore, keep your mouth in a high state of health, and seek frequent examinations for monitoring your oral tissue health.
The discontinuation of bisphosphonate therapy should only be done in consultation with your physician. Since the effects of these drugs persist many years after you have stopped taking them, discontinuance will not likely heal existing lesions and it may not help prevent lesions in the future.
All of this information is very new because BON is an emerging condition and I will keep you informed of new developments in prevention and therapy.
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