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Prescribed Drugs Affect Tooth Movement
The use of drugs in the treatment of medical conditions or diseases may have an effect on a patient’s orthodontic treatment, presenting challenges other than those related to their malocclusion. For example, drugs that hinder bone metabolism (remodeling) are used in the treatment of cancer (such as breast cancer, kidney cancer, lung cancer, multiple myeloma, and melanoma), Paget's disease of bone, osteogenesis imperfecta, fibrous dysplasia, osteoporosis and osteopenia. Orthodontic tooth movement depends upon osteoclast (bone removing cells) activity to remove bone from the pressure areas on a root and osteoblasts (bone forming cells) to build new bone on the tension areas on a root. Drugs altering a person’s bone metabolism may slow or even stop orthodontic tooth movement.
This may not seem to be a pressing concern. However, ever-increasing numbers of adults are seeking orthodontic treatment and millions are taking medications that deter bone metabolism. Fourteen million women and 2 million men are taking oral bisphosphonates for the prevention of skeletal concerns related to osteoporosis and tens of thousands of patients are also receiving bisphosphonate therapy as part of their chemotherapeutic regimens for the treatment of various types of cancer. The use of bisphosphonates has reduced the risk of osteoporotic fractures by up to 50% and has made a significant impact in the alleviation of cancer morbidity.
Having an affinity for calcium, bisphosphonates are maintained at higher levels in bone with a greater level of remodeling like the bone in the upper and lower jaws. Upon removing bone, osteoclasts die when ingesting bone with bisphosphonates. Recent evidence indicates that bisphosphonates may adversely affect the healing potential of bone by reducing its blood supply. Intravenous doses of bisphosphonates, used in the treatment of cancer, are as much as 12 times more than that of oral doses, used to treat osteoporosis.
The Food and Drug Administration has issued precautions regarding the use of bisphosphonates and osteonecrosis (dead bone) of the jaws. Most of the osteonecrosis cases that have been reported are linked to the intravenous drug treatment and occur within the mouth. Patients receiving intravenous bisphosphonates, experience a 1-10% incidence of osteonecrosis. Though bisphosphonates taken orally are believed to be a lower risk, length of use, dose and frequency increase the risk of osteonecrosis. Oral administration over three years is considered to be a red flag. Osteonecrotic areas in the jaws may spontaneously appear and are usually not treatable. Osteonecrosis lesions are more common in the lower jaw in areas where the gum is thin. Since bisphosphonates are absorbed, stored, and excreted unchanged from the body, high concentrations of bisphosphonates remain in the bone for long periods (more than 10 years). Discontinuing bisphosphonate use for a period of time before orthodontic treatment will not reduce the risk of osteonecrosis of the jaw.
The use of bisphosphonates may put a patient at risk for orthodontic treatment, especially if surgery (the removal of teeth, implant placement, or gum surgery) is needed as part of the orthodontic treatment plan. Even a removable orthodontic appliance like a retainer can be a problem if it causes a sore spot on the gums that exposes bone. An orthodontic patient may need to change their treatment plan during the course of orthodontic treatment, when treatment for a recently identified medical condition or disease requires the use of bisphosphonates. A blood test (CTX) is useful to assess the possibility of tooth movement and the level of risk for osteonecrosis. CTX levels greater than 150 pg/ml are associated with minimal to no risk.
Interestingly, medications that may be a detriment to orthodontic treatment may also be an asset when used locally. The movement of certain teeth may be prevented using bisphosphonates topically, aiding treatment or helping with retention.
This patient is a 55-year-old female with no significant medical problems except a 5-year history of being treated for osteoporosis with oral bisphosphonate. Her CTX level was 150 pg/ml, indicating a minimal to no risk for orthodontic treatment. Treatment was limited to her front teeth using fixed appliances (braces). The course of treatment was without incident and was completed in a normal amount of time, 9 months. The before treatment photograph is on the left and the after treatment is on the right.
