Bisphosphonates (also called diphosphonates) are a class of drugs that prevent the loss of bone mass, used to treat osteoporosis and similar diseases. They are called bisphosphonates because they have two phosphonate (PO3) groups and are similar in structure to pyrophosphate.
Evidence shows that they reduce the risk of osteoporotic fracture in those who have had previous fractures however do not reduce fracture risk in those with osteoporosis who have not previously had a fracture.
Bone undergoes constant turnover and is kept in balance (homeostasis) by osteoblasts creating bone and osteoclasts destroying bone. Bisphosphonates inhibit the digestion of bone by encouraging osteoclasts to undergo apoptosis, or cell death, thereby slowing bone loss.
The uses of bisphosphonates include the prevention and treatment of osteoporosis, osteitis deformans ("Paget's disease of bone"), bone metastasis (with or without hypercalcaemia), multiple myeloma, primary hyperparathyroidism, osteogenesis imperfecta, and other conditions that feature bone fragility.
Of the bisphosphonate that is resorbed (from oral preparation) or infused (for intravenous drugs), about 50% is excreted unchanged by the kidney. The remainder has a very high affinity for bone tissue, and is rapidly adsorbed onto the bone surface.
People taking oral bisphosphonates, a type of drug used to treat osteoporosis, osteopenia and Paget's disease of bone, should be aware of potential risks when undergoing certain dental procedures, according to guidelines published in this month's Journal of the American Dental Association (ADA).
Relying on a small but growing number of reports linking bisphosphonate drugs to incidences of osteonecrosis of the jaw (dead bone tissue), a panel of experts convened by the ADA believes dental patients who are taking oral bisphosphonate drugs should discuss the risks they face when undergoing procedures that involve the jaw bone, such as tooth extraction or placing implants, with their dentist. Dentists and their patients should carefully consider these procedures, as well as alternative dental therapies. Patients may also want to discuss this information in the context of their overall health and treatment options with their physician.
The ADA recommends that a comprehensive oral evaluation be carried out on all patients about to begin therapy with oral bisphosphonates (or as soon as possible after beginning therapy), and that patients on these drugs be educated on maintaining oral hygiene, which is the best way to prevent oral diseases that may require dental surgery.
The ADA notes that dentists, generally, will not need to modify dental treatments based solely on oral bisphosphonate therapy. Further, patients should understand that the risk for developing osteonecrosis of the jaw is considered very small and that the vast majority of patients taking an oral bisphosphonate do not develop any oral complication.
