Monday, May 9, 2011

An Unexpected Complication

I seem to be specializing in Strange Maladies Of Indeterminate Origin. Last week, I visited my dentist for a routine cleaning and examination. I also got the annual full set of X-rays. The picture of one of the mandibular canines (tooth #27) caught the attention of the dentist, who forwarded it to an endodontist, who delivered a diagnosis of external root resorption. This is a poorly understood (especially by me) phenomenon, in which the tooth appears to be destroying itself from within, "apparently initiated by a peculiar inflammatory hyperplasia of the pulp", by one account. This could be an autoimmune disorder, but it is more commonly believed to be ultimately caused by trauma, where "trauma" is defined to include the wearing of orthodontic appliances -- which I did, back in the day. If the damage is not too advanced, the tooth can be rescued by means of a root canal; otherwise, it must be extracted and, nowadays, typically replaced by an implant. In my case, the endodontist would normally pass me off to an oral surgeon for extraction. But...

But I am receiving bisphosphonate therapy, to counteract the effects of the cancer on my spine. Normally, special cells called osteoclasts clean up old bone mass, making way for new bone created by the counterpart osteoblasts (a process known as "bone turnover"). Myeloma appears to overstimulate the osteoclasts, which begin to outperform the osteoblasts, creating many lytic lesions -- holes -- in the bone. This is obviously a Very Bad Thing, leading in my case to a greatly enhanced risk of spinal compression fractures. Bisphosphonates such as the one I am getting, Aredia, attempt to solve this problem by suppressing the osteoclasts, which is a mixed blessing, since bone turnover is as a result reduced everywhere, meaning that the bones are more brittle and are slower to heal than they should be. Apparently, this is especially a problem where surgical procedures performed on the jaw, such as a tooth extraction, are concerned, leading to a condition known as "bisphosphonate-related osteonecrosis of the jaw". The wounded jaw does not heal, and eventually the bone in the vicinity of the wound dies. This is another Very Bad Thing. So oral surgeons are understandably reluctant to perform extractions on patients receiving bisphosphonates.

The effect of bisphosphonates on bone turnover is typically gauged by a serum CTX test; patients getting bisphosphonates will show much lower than normal CTX numbers. A sufficiently lengthy drug holiday might return serum CTX to a range acceptable to an oral surgeon; a temporary root canal might be necessary to stave off disaster in the interim. The question is whether the oncologist can be persuaded to declare such a drug holiday. I was on track to continue receiving Aredia until at least the end of this year, for reasons of course completely unrelated to dentistry. My next visit with the oncologist should be much more interesting than usual, for this and certain other reasons, which I will discuss in due time.

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