Cone Beam Imaging | Fallacies in Interpretation: Part 1

Advances in technology from the wheel to the computer, on which I am composing this article, have changed human life in profound and mostly beneficial ways.  This is certainly true of the technological advances in dentistry – a relatively recent and dramatic example being Cone Beam Imaging devices. Although cone beam imaging has been around for some time, it is only recently that advances in computer hardware and sophisticated software algorithms have made cone beam computed tomography (CBCT) accessible and useful in dentistry. I expect that most of you are now not only aware of CBCT, but using this technology, either from third parties or perhaps in your own office. Unfortunately, manufacturers and many lecturers and authors have inferred or actually stated that the domain expertise from two-dimensional periapical radiography is transferable to the CBCT interpretation task.  The evidence from carefully done studies in medicine along with the errors in research design and interpretation of clinical cases suggests otherwise. Over the past several years, one of the most pervasive – and disturbing – claims made by new users and many pundits lecturing on the virtues of CBCT technology in the endodontic domain, is the ability to see ‘cracks’ in CBCT studies that could not otherwise be observed. Fig. 1 This is a false assertion and an unrealistic expectation of this technology.  Because of this common misconception and misunderstanding of the limitations of this technology, coupled with the mistaken pseudo-domain expertise brought from two-dimensional PA radiography, I routinely get requests for cone bean imaging from referring dentists to confirm or deny the suspected presence of a crack.  Let me assert clearly that if there are findings from a tooth that is actually cracked observable on a CBCT reconstruction, and not an artifact, the crack will be so obvious that the CBCT scan was not required for its diagnosis.

Cone Beam Imaging Knowledge is Critical

Having an in-depth understanding of how cone beam imaging data is acquired, processed and reconstructed would be very helpful in understanding that what is commonly purported to be a crack, is simply an artifact. It can also be a combination of artifacts such as attenuation, beam hardening, reconstruction artifact, ringing artifact, motion artifact and noise. What one can often observe on CBCT reconstructions that may not be observable on conventional 2D images, are findings that support the possible diagnosis of a ‘cracked tooth’. However, one cannot rely on the study to ‘see’ the crack.  Fig. 2, Fig. 3, Fig. 4, Fig. 5 Why is that? Cracks in endodontically treated teeth, specifically vertical root fractures and not trauma for example, are on the order of 20 to 100 microns wide.  The voxel resolution of the best scanners today is only 76 microns – this is not likely to improve any time soon.  These cracks are simply too small to detect with any reliability. Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10 Look for in depth educational offerings on cone beam imaging from Spear Education coming soon. Glen E. Doyon, DMD, Spear Contributing Author [ www.CMSEndo.com ]