Osteoporosis is a condition that affects over 200 million people worldwide. Today, the most common medication used for treating osteoporosis is bisphosphonates (BPs). Initially developed over 100 years ago as a water softener, BPs came into prominence in the 1960s for the treatment of low bone density and other bone fragility disorders. The first generations demonstrated limited efficacy, but later generations showed better and better results at preserving bone density and strength. Modern BPs are powerful enough to provide a therapeutic effect for an entire year with just one injection.
As these newer formulations were developed and came into use in the 70’s and beyond, a strange new side effect started to appear. Patients on long-term BP use who had a tooth removed would sometimes find the extraction site would not heal, resulting in progressive bone loss in the jaw that often proved difficult, if not impossible, to manage. This condition was termed Osteonecrosis of the Jaw, or ONJ, and if it could be tied to BP use, Bisphosphonate-Related ONJ, or BRONJ.
As with any newly-discovered health condition, there was a lot of alarm and not much information. (Sound like anything that’s happened recently?) As time went on and more knowledge was gained, the alarm subsided to more of a healthy caution, and some basic guidelines started to emerge. Unfortunately we’re still not where we want to be in managing BRONJ, which has proven to be a rather mercurial disease with limited treatment options.
Bisphosphonates work to preserve bone by slowing down the cells that eat away, or resorb, bone. These cells are known as osteoclasts (in diagrams they kind of look like the ghosts in Pac-Man, appropriately). Cells that build bone are called osteoblasts, and the two work together to continuously remove and build bone. At any point in time, up to 10% of the bone in the body is being remodeled. Small stress fractures can occur from regular activity, a need to strengthen an area can arise from various forces, and even aging can stimulate bone to be added here and taken away there.
On the surface it would seem rather straightforward that limiting bone resorption would allow more bone development and thus limit the effects of osteoporosis. The problem is that not all bone is created equal; sometimes bone is formed improperly, or becomes contaminated, and needs to be removed and rebuilt. If the cells that remove bone are inhibited, this defective bone is allowed to stay.
Even a healthy mouth is full of bacteria, fungi, and other pathogens. When a tooth is extracted the resulting socket exposes bone to the oral environment, allowing these pathogens to gain a foothold. As the extraction site heals and new bone forms, any trapped contaminants can lead to the bone dying, or necrosing. In patients taking BPs, this can create a runaway process where even adjacent, healthy bone dies, which is the condition called ONJ.
Unfortunately, despite all of our increased knowledge, ONJ has proven notoriously difficult to treat. Research continues, but focus has been placed heavily on risk assessment and prevention. The number one recommendation for BP users is to maintain impeccable oral health (isn’t this a good idea for everyone?). This limits the likelihood that a tooth might need to be extracted, and keeps oral pathogens to a minimum.
It turns out that not all BPs are created equal, either. The orally administered versions (common ones include Fosamax and Actonel) have shown to carry a very low risk of ONJ following oral surgery. So while adequate caution should always be applied, most surgical procedures are not contraindicated in this population. The intravenous (IV) versions (Aredia, Reclast and Zometa, among others) are a different story. Often these are prescribed for more serious conditions such as bone cancer, multiple myeloma, and severe osteoporosis. The risk for ONJ in this population is significantly higher and even routine oral surgery (extractions) should be avoided whenever possible. Keep in mind that the risk is still low, but the effects of ONJ can be devastating so an abundance of caution is certainly advised.
Other factors that can contribute to ONJ are smoking, BP use of three years or longer, steroid use along with BP use, diabetes and other chronic health conditions affecting healing. Although dental extractions are the most common initiating agent, chronic inflammation can lead to ONJ as well. Ill-fitting dentures that lead to damaged and inflamed tissue has been shown to cause ONJ in rare cases.
As with any medication, the benefit versus risk profile must be evaluated. For most patients, the benefits of BPs usage outweigh any risks. A visit with your dentist is critical to identify any dental issues that may put you at risk for ONJ, as well as a discussion of steps you can take to keep that risk as low as possible. “An ounce of prevention is worth a pound of cure” has never been more true than with ONJ.
– Dr. McGann