Some orthodontists may be exposing young patients to unnecessary radiation when they order 3-dimentional (3-D) x-ray imaging for simple orthodontic cases before considering traditional 2-dimentional (2-D) imaging, suggests a paper published recently in Dentomaxillofacial Radiology. 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, said Dr. Sunil Kapila, lead author and chair of the department of Orthodontics and Pediatric Dentistry at the University of Michigan (U-M) 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 Dr. 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, Dr. Kapila said. 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 (µSv) or more compared to 4 to 40 µSv for an entire series of 2-D x-rays required for orthodontic diagnosis, Dr. Kapila said. Considering that the average US population is exposed to approximately 8 µSv of background radiation a day, 200 µSv 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,” said Dr. Erika Benavides, a board-certified oral and maxillofacial radiologist who reads the CBCT scans taken at the U-M 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.”
Both Drs. Kapila and Benavides said when used judiciously, CBCT is an invaluable tool with a definite place in orthodontic treatment planning. Dr. Kapila said that the paper published by he and his colleagues advocates “a balanced approach to utilizing CBCT in our patients.” While other patients could also benefit from 3-D imaging, the decision to scan these patients should be made on a case-by-case basis after a clinical exam and evaluation of the specific patient needs, particularly when 2-D imaging has shown that additional 3-D information would result in a demonstrable benefit that would likely alter the treatment plan.
(Source: ScienceDaily. January 30, 2011)