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CAD/CAM international magazine of digital dentistry

I opinion _ use of CBCT 12 I The European Asso- ciation for Osseointe- gration (EAO) recently updated its guidelines fortheuseofdiagnostic imaging in implant dentistry, which now include cone-beam computed tomography (CBCT) and are sup- posed to address the AsLowAsisReasonably Achievable principle as well as to optimise both conventional radiogra- phy and new proce- dures.Acommentaryby Prof.KeithHorner,UniversityofManchester,UK. _CBCT is the most significant development in dental imaging during the last 25 years. It brings cross-sectional imaging into the dental practice andhasobvioususesinimplantdentistry.Concerns havebeenraised,however,overtheradiationdoses, whichareusuallyhigherthanthoseofconventional dental radiography. When the word “radiation” is used, alarm bells ring for everyone. One of the most common ques- tions asked by dentists is how the dose of one X-ray examination (e.g. a panoramic radiograph) relates to another (e.g. CBCT). This is almost impossible to answer because there is a wide range of possible doses from any type of X-ray examination, reflect- ing differences in equipment, the image receptor, the field of view and so on. Recent reviews indicate thatdosesfromCBCTaretypicallyanorderofmag- nitudegreaterthanthosefromconventionaldental radiography. The health risks from such exposures are also proportionately higher; although we can perhaps console ourselves by remembering that risk falls with patient age, and that many implant patients are in the older age groups. The foundations of radiation protection of pa- tientsarejustificationandoptimisation.Justification embodies the principle that all exposure to X-rays should give a positive net benefit to the patient. It is implicit within this that the X-ray imaging strategy should be “prescribed” for each patient andthereforethatnoimagingshouldbeperformed until a history and clinical examination have been performed. Referral criteria are an essential aid to the justification process, being clinical guidelines based on, at best, a solid body of evidence or, where the evidence is lacking, consensus. Optimisation is the principle that all exposure should be as low as reasonably achievable. As radiation exposure fac- tors are reduced, image quality will fall, but lower- ingexposuretoapointatwhichimagequalityisstill adequateisanimportantstrategy,aswellascutting down the size of the field of view. So, where do we go from here? CBCT is a great technological advance, but that does not mean we must use it if a conventional radiograph, or good clinical examination, would be sufficient. We have to recognise that regulatory authorities dealing withradiationinEuropeareawareofCBCTindental practicesandarekeepingawatchfuleyeonhowwe use this technology. The best way for us to demon- strate that we are appropriate users of CBCT is to follow the principles of justification and optimisa- tion—and to show that we follow them. This means only using CBCT when it is going to answer a ques- tion that cannot be answered by other methods involving less, or no radiation. When we use CBCT, we should never just “press the button” using a standard exposure for everyone, but we should adjust the exposure fac- tors to a level that gives adequate image quality andusethesmallestappropriatefieldofview.These simple steps will reassure our patients that we have their best interests at heart; that is what we really want—isn’t it?_ CAD/CAM 4_2012 Prof. Horner addressing the audience of a EAO pre-congress course on CBCT in implant practice. (DTI/Photo Daniel Zimmermann, DTI) Use of CBCT in implant dentistry shouldfollowjustificationandoptimisation Author_ Dental Tribune International Keith Horner is Professor of Oral and Maxillofacial Imaging at the University of Manchester’s School of Dentistry.He was also a contributor to the latest revision of the EAO’s guidelines for the use of diagnostic imaging in implant dentistry. CAD/CAM_about the author