Some orthodontists may be exposing young patients to unnecessary radiation when they order 3-D X-ray imaging for simple orthodontic cases before considering traditional 2-D imaging, a paper published by U-M faculty suggests.

There is ongoing debate in the orthodontic community over if and when to use cone beam computed tomography (CBCT) for orthodontic diagnosis and treatment planning, says Dr. Sunil Kapila, lead author of the paper and chair of the Department of Orthodontics and Pediatric Dentistry at the School of Dentistry.

A very small number of orthodontists utilize the 3-D imaging on a routine basis when developing a treatment plan, and this raises concerns of unnecessary radiation exposure. In contrast, the evidence summarized in Kapila’s paper suggests that 2-D imaging would suffice in most routine orthodontic cases. One of the tradeoffs for the superb 3-D images is higher radiation exposure, Kapila says.

The amount of radiation produced by 3-D CBCT imaging varies substantially depending on the machine used and the field of view exposed, and some clinicians may not realize how much higher that radiation is compared to conventional radiographs. One CBCT image can emit 87 to 200 microsieverts or more compared to 4 to 40 microsieverts for an entire series of 2-D X-rays required for orthodontic diagnosis, Kapila says. Considering that the average U.S. population is exposed to approximately 8 microsieverts of background radiation a day, 200 microsieverts equates to about 25 days worth of cosmic and terrestrial radiation.

“Most of the patients who need orthodontic treatment are young adults and pediatric patients,” says Dr. Erika Benavides, clinical assistant professor in the Department of Periodontics and Oral Medicine. Benavides is the board certified oral and maxillofacial radiologist who reads the CBCT scans taken at the School of Dentistry. “Keeping in mind that the radiation received has cumulative effects, adding unnecessary radiation exposure to the patient may result in a higher biological risks, particularly in the more susceptible young children. This is why selecting the patients that would benefit the most from this additional exposure needs to be done on a case-by-case basis.”

Both Kapila and Benavides said when used judiciously, CBCT is an invaluable tool with a definite place in orthodontic treatment planning. The paper published by Kapila and his colleagues advocates “a balanced approach to utilizing CBCT in our patients,” Kapila says.

The paper, “The current status of cone beam computer tomography imaging in orthodontics,” recently was published in the journal of Dentomaxillofacial Radiology. Co-authors are R.S. Conley, associate professor at the School of Dentistry, and W.E. Harrell; both board certified orthodontists.