Claus et al conducted a case-control study of 2783 subjects and reported an association between an increased risk of intracranial meningioma and prior exposure to dental bitewing and panoramic radiographs but not to full-mouth radiographs.1 The brain exposure from 4 bitewing radiographs is approximately 0.07 milligrays (mGy) and that from a panoramic radiograph is approximately 0.02 mGy. Alternatively, a full-mouth examination, comprised of 16 to 20 views, including 2 to 4 bitewing radiographs, delivers approximately 0.24 mGy to the brain (Dose reconstructions were made using D-speed film and round collimation, typical of later decades of the last century. With contemporary techniques exposures are less than half these values). Nevertheless, no association was found between full-mouth examinations and meningiomas in the study by Claus et al.1 It is difficult to reconcile this inconsistency.
Brain exposures from bitewing and panoramic radiographs are miniscule compared with natural background radiation (average effective dose of 3.1 millisieverts [mSv] per year2) and with head computed tomography scans (approximately 43 mGy-75 mGy3), approximately 19 million of which are made annually in the United States.2 It is important to note that extensive study of Japanese atomic bomb survivors and other exposed populations has not reliably demonstrated epidemiologic evidence of an increased cancer risk below 100 mSv.4 It is not plausible that an additional 0.02 mGy to 0.07 mGy contributes measurable risk.
Meningiomas can cause referred pain to the orofacial region.5 A patient with such orofacial pain may receive panoramic or intraoral radiographs during the course of their care. One or few periapical radiographs could be easily confused with bitewing radiographs. It may be that radiographs do not cause meningiomas but rather the presence of the tumors triggers the need for radiographs. Few such additional exposures in the patients with meningioma may explain the reported association.
Radiographs are an indispensable component of dentistry. We are concerned that inappropriate conclusions drawn from the study by Claus et al,1 and the press coverage it has received, may lead to the suboptimal diagnosis of dental disease and to unnecessary compromise of patient care.
We thank Dr. John Ludlow for dose reconstructions and Dr. Sotirios Tetradis for suggesting a link between meningioma and orofacial pain.