3D X-Rays for Children Should Be Used Sparingly

Some orthodontists may be exposing young patients to unnecessary radiation when they order three-dimensional (3D) X-ray imaging for simple orthodontic cases before considering traditional 2D imaging, suggests findings from new research.

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, reported Dr. Sunil Kapila, lead author of the study and chair of the department of orthodontics and pediatric dentistry at the University of Michigan (U-M; Ann Arbor, USA) School of Dentistry.

A very small number of orthodontists utilize the 3D 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 article suggests that 2D imaging would suffice in most routine orthodontic cases. One of the tradeoffs for the outstanding 3D images is higher radiation exposure, according to Dr. Kapila.

The amount of radiation generated by 3D CBCT imaging varies considerably depending on the machine used and the field of view exposed, and some clinicians may not comprehend how much higher that radiation is compared to traditional radiographs. One CBCT image can emit 87 μSv to 200 μSv or more compared to 4 μSv to 40 μSv for an entire series of 2D X-rays required for orthodontic diagnosis, according to Dr. Kapila. 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, clinical assistant professor in U-M's department of periodontics and oral medicine. Dr. Benavides is the 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 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 Drs. Kapila and Benavides said when used judiciously, CBCT is a very valuable tool with a definite place in orthodontic treatment planning. The article written by Dr. Kapila and his colleagues advocates "a balanced approach to utilizing CBCT in our patients.”

To that end, the investigators reviewed the existing data on CBCT and found that this type of imaging is typically recommended in cases that include those with impacted teeth, temporomandibular joint disease, craniofacial abnormalities, and jaw deformities. While other patients could also benefit from 3D 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 2D imaging has shown that addition 3D data would result in a demonstrable benefit that would likely alter the treatment plan.

"There is nothing published on current usage patterns,” Dr. Kapila said. "Most of the information is anecdotal. Some clinicians and orthodontists are using this technology routinely, but I believe that most of those that use 3D imaging use it fairly judiciously,” Kapila said.

The patients who are scanned at U-M Dental School are referred after clinical evaluation by dental specialists and the area to be scanned is carefully limited, according to Dr. Benavides.

The study was published January 2011 in the Journal of Dentomaxillofacial Radiology.

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