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EDITORIAL THE PUSH/PULL SURROUNDING CONE BEAM COMPUTED TOMOGRAPHY (CBCT) By Dr. Gerald Nelson, Editor in Chief, PCSO Bulletin W ith CBCT, orthodontists are faced with a rapidly developing technology that stimulates interesting discussion among colleagues and the general public. Do you feel that you are being pressured into ordering 3D radiograms for your patients? The following are comments heard on the street: • UCSF takes a 3D scan three times on every patient. • A recent New York Times article criticizes orthodontists who take a CBCT on every patient. • In our 2D Berkeley practice, several patient families have mentioned the article in worried tones. • Recent studies have shown that diagnosis and treatment planning of impactions is enhanced with use of 3D images. • A paper in the American Journal of Orthodontics and Dentofacial Orthopedics (AJO-DO) exhibits “Four Curious Cases” in which 2D x-rays were inadequate to screen for important findings. • A PCSO Southern Region presentation by Dr. Mah and Dr. Hatcher showed many cases in which the use of CBCT was critical to the treatment planning. Most readers were not in the field at the time of the revolutionary introduction of the cephalometer to orthodontics. The controversy in the specialty around the routine use of lateral headfilms was no less confusing or passionate than what we are currently witnessing for CBCT. The radiation dose for headfilms and the number taken in the early years is surprising today. According to orthodontic historian Norman Wahl, T. Wingate Todd (the originator of the SPRING 2011 • PCSO Bulletin Image from Kodak 9500 cephalometer) and his assistant, B. Holly Broadbent Sr., exposed more than 4,500 children annually, “thus establishing standards of normal development at any period of childhood.” Dr. Broadbent introduced the technique to the specialty in 1931. The article, “A New X-Ray Technique and Its Application to Orthodontics,” is available as a free download at the Online Angle Orthodontists, www.angle.org. (Volume 1, Issue 2). It took many years before the specialty accepted the routine use of lateral headfilms in orthodontic diagnosis. CBCT AND DIAGNOSIS A study done at UCSF by Dr. Erik Haney (Fairfax, CA) in 2009 involved orthodontists and oral surgeons reviewing stations with 2D and 3D images of canine impactions. Twenty-five impacted teeth had had both 11 EDITORIAL types of x-rays, which were distributed around the room randomly. Of the treatment plans for extraction of the impacted tooth using the 2D images, 53% were changed to recovery when viewed in 3D. The recommended vector of force application also differed between the two image techniques. Since then, other studies have confirmed the value of 3D scans for impacted teeth. Another study at UCSF confirmed the value of 3D scans to evaluate root positions achieved with orthodontic appliances. We know that a 2D panogram has serious distortions when evaluating root positions. The patient benefit of using CBCT is established. The question is, when should you employ the technique? One suggestion is to first take a 2D pano and ceph and then use these films to make a decision to take the 3D scan. This approach has some merit, and there are a couple of machines available that can do both the 2D and 3D image. However, the “Four Curious Cases” presented in the April 2010 AJO-DO are a bit unnerving, as the 2D image missed some problems. LIABILITY R isk is an issue. A primary risk is that you will miss something important in your diagnosis with 2D. When a disgruntled patient goes to an attorney to take action against an orthodontist, the typical first action is to order a CBCT scan to see if any pathology was missed. The second risk is a less than ideal treatment plan, since we know that treatment plans change with the benefit of 3D images. The third liability is the responsibility to detect pathology in 12 the entire 3D volume (not to diagnose every aberration, but to notice and refer when appropriate). We handle this at UCSF by ordering radiologist reports. These reports are very instructive, and after reviewing a few dozen of them, one becomes quite comfortable evaluating the image on one’s own. Of course, we have similar responsibilities with 2D images. A lateral headfilm and panogram can reveal obscure pathologies that we should be ready to notice. The concern of one’s responsibility for the 3D images will fade as we become more comfortable with reviewing the images. As Dr. Hatcher says, the key is the software. Current programs are easy to use, and getting better every year. RADIATION DOSE R adiation is a concern, and the public is alerted to this issue. For the orthodontist in private practice, this means educating the patient family when a 3D x-ray is proposed. In fact, the radiation dose from 3D scans is not out of line, taking into account the benefits. Doses these days are under 200 microsieverts, which is comparable to an orthodontic 2D series that includes a full-mouth series of x-rays. FINAL THOUGHTS O rthodontists must recognize that this technology offers important benefits to the patient, and we need to move toward utilizing CBCT on all our patients— and developing our diagnostic skills appropriately. The technology offers an excellent tool to improve our treatment plans and avoid missing important pathology in our patients. S PCSO Bulletin • SPRING 2011