We appreciate the comments made by Dr. Surabian regarding our article. Dr. Surabian expresses his disappointment about the lack of endorsement on our part of the serum C-telopeptide test of type I collagen (CTX) as a marker for dental treatment decisions. As stated in our article, we maintain our position.
Several reasons guide our judgment. Bisphosphonates suppress bone remodeling due to the inhibition of osteoclasts. The CTX is an electrochemilu-minescence assay that measures the level of collagen type I C-telopeptide in serum, a product of bone collagen degradation, and measures systemic bone resorption. This measurement represents bone resorption for the entire skeleton, not exclusively the resorption levels in the jawbones. Therefore, the lower the CTX levels, the greater the suppression of bone resorption.
The range of normal levels of CTX in women aged 18– 29 years is 64 to 640 picograms per milliliter, 60 to 650 pg/mL in women aged 30 to 39 years, and 40 to 465 pg/mL in women aged 40 to 49 years. In men in the same age groups, the levels range from 87 to 1,200 pg/mL, 70 to 780 pg/mL and 60 to 700 pg/mL, respectively. In addition, the range for men aged 50 to 68 years is 87 to 345 pg/mL.1
There is a tremendous variability of the CTX levels from patient to patient. Individual genetic characteristics may influence these levels, as well as disease characteristics and serum levels of CTX throughout the day hours. Using Marx’s2,3 recommendations, it would be safe to treat patients when the levels would be above 150 pg/mL, and not so safe when the levels are below 100 pg/mL. These recommendations do not distinguish between male and female patients and do not consider whether those people in whom a 60 pg/mL or even a 40 pg/mL still would be considered within a "normal range" for the CTX test.
The recommendation for making dental treatment decisions based on the results of the CTX test comes from a study of a small sample of 30 patients who had received bisphosphonate medications for several years.2 Information on the CTX levels for each of the patients before they started the use of bisphosphonate is not available. There is no control group to validate the recommendations. Therefore, there is no guarantee that the results observed in the study were not due to chance. Consequently, the association between a lower CTX level and osteonecrosis of the jaw is merely a clinical observation and could well be further defined by a case control study comparing people on bisphosphonates who develop osteonecrosis and those who do not develop osteonecrosis.
If we consider that less than 0.01 percent of patients taking oral bisphosphonates develop osteonecrosis, perhaps it would be better for the dentists and patients to make a clinical judgment rather than to base their decision on the results of the CTX test. We would like to have a reliable serum marker for bis-phosphonate osteonecrosis, but this is not yet available based on scientific evidence.4 Thus, using good clinical judgment, making correct indications of dental treatment using standard of care and establishing good relationships with our patients are the best guidelines available for the dental management of the care of patients taking bisphosphonates.
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