CBCT: Dispelling the Fear
By Bruno Azevedo, DDS MS
Cone Beam Computed Tomography (CBCT) is modern dentistry’s premier imaging diagnostic tool, integrating significantly into clinical endodontics, research, and graduate education. The advantages of incorporating CBCT imaging in clinical practice—improving diagnosis accuracy, enabling detailed anatomy mapping, enhancing surgery planning, and optimizing root canal therapy outcomes—are substantiated by robust research. Nevertheless, a persistent challenge remains: apprehension regarding radiation dose. Despite its documented and substantial benefits, CBCT imaging continues to face stigmatization stemming from contested and increasingly discredited concepts such as the Linear Non-Threshold Theory (LNT) and its derivative, the As Low As Reasonably Achievable (ALARA) principle.
The primary obstacle impeding the complete acceptance of CBCT imaging within endodontics is unfounded concern regarding low radiation doses in dental applications. Some clinicians and educators continue to refuse patient scanning, citing potential radiation damage and invoking ALARA as justification for avoiding CBCT acquisition. This behavior generates radiophobia-driven inefficiencies throughout the healthcare field, manifesting as patients declining necessary CBCT imaging and practitioners avoiding ordering cbct scans even when clinically indicated. The consequences include delayed diagnoses, suboptimal treatment planning (including missed root fractures and overlooked complex canal anatomy), and ultimately compromised patient outcomes. This apprehension persists despite compelling evidence that CBCT doses (approximately 20–200 μSv) measure thousands of times below established biological harm thresholds and substantially lower than natural background radiation exposure.
For over six decades, many practitioners have uncritically accepted the fundamentally flawed premise underlying LNT theory: that any radiation exposure, regardless of magnitude, carries proportional cancer risk. Historical examination reveals that LNT adoption stemmed from methodologically unsound studies (such as Herman Muller’s fruit fly experiments) and Cold War-era political imperatives rather than scientific consensus—a fact often overlooked by its proponents. The theory demonstrates significant biological shortcomings, notably disregarding DNA repair mechanisms. These mechanisms represent a cornerstone of cellular biology, supported by Nobel Prize-winning research documenting more than 150 genes involved in DNA repair processes, which directly contradicts LNT’s assumption of irreparable damage. Furthermore, LNT fails to account for dose-rate effects: low-dose-rate radiation (characteristic of all dental imaging modalities) permits cellular repair mechanisms to function effectively, unlike high-dose exposures, invalidating LNT’s rate independence assumption.
The ALARA principle, derived directly from the LNT model, faces mounting criticism for its inappropriate application in dental imaging, particularly regarding CBCT for endodontic purposes. Rigid adherence to ALARA frequently generates clinically counterproductive practices, notably reducing image resolution to minimize radiation exposure, consequently compromising detection capabilities for critical diagnostic features, including root fractures, complex canal anatomy, periapical lesions, and resorptive defects. These suboptimal imaging protocols increase the risks of missed diagnoses, treatment delays, and procedural complications.
The dental industry bears partial responsibility for perpetuating these misconceptions. By adhering to the LNT model and ALARA principle, dental imaging manufacturers excessively market “low-dose” imaging protocols that often intensify radiophobia by prioritizing theoretical radiation risks over diagnostic efficacy. This continues despite accumulating scientific evidence demonstrating that radiation doses in dental modalities, including CBCT (typically below 100 μSv) fall substantially below thresholds for biological harm. Marketing campaigns emphasizing incremental dose reductions as primary safety features—rather than investing in technologies enhancing resolution or optimizing risk-benefit ratios—foster false security based on clinically insignificant biological gains. For instance, reducing CBCT doses from 50 μSv to 30 μSv provides no measurable health benefit, yet such claims dominate product advertising, misleading practitioners and patients into equating lower doses with improved safety regardless of diagnostic quality implications.
Patient apprehension regarding ionizing radiation, however minimal the exposure, remains understandable. Popular media frequently exacerbates these concerns through fictional narratives depicting radiation as generating mutations, monsters, and apocalyptic scenarios, reinforcing perceptions of inherent danger. Endodontists must avoid perpetuating this narrative and instead emphasize scientific evidence supporting CBCT imaging benefits. The American Dental Association’s recent advocacy for discontinuing routine lead apron use during dental imaging acquisition, mirroring the 2019 policy shift in medical imaging, highlights technological advancement and enhanced understanding of radiation safety. Eliminating protective aprons signals confidence in contemporary safety protocols, countering misconceptions regarding dental radiography hazards.
In contemporary endodontic practice, practitioners require confidence when discussing technological benefits and addressing radiation exposure concerns. Terminology modifications represent an initial step—replacing anxiety-inducing terms like “X-rays” and “CT scans” with “pictures” and “3D pictures of your tooth.” Additionally, endodontists should emphasize CBCT imaging’s clinical advantages, including its capacity to generate detailed three-dimensional representations of root canal architecture, detect fractures, and identify periapical lesions frequently imperceptible through conventional two-dimensional radiography. By explaining how CBCT enhances diagnostic precision and treatment planning, practitioners can redirect focus from theoretical risks toward tangible patient care benefits.
Patients benefit from understanding that their bodies possess sophisticated mechanisms for repairing DNA damage caused by low-dose radiation exposure and that decades of research demonstrate no measurable risk below 100,000 μSv—substantially exceeding CBCT exposure levels. Incorporating updated professional guidelines, including the ADA’s recommendation against routine lead apron use, reinforces confidence in safety protocols while streamlining clinical workflows. Clear, empathetic communication remains essential: endodontists should explain that avoiding necessary imaging due to unfounded concerns potentially delays proper diagnosis and may necessitate more invasive treatments subsequently. Providing evidence-based information in accessible terminology while highlighting CBCT benefits for precise diagnosis and minimally invasive intervention effectively addresses patient concerns while fostering trust in modern dental imaging practices.
In conclusion, ALARA and LNT have have generated considerable confusion regarding the potential biological risks of low-dose radiation. The result is a cycle of radiophobia-driven inefficiencies, where fear of negligible risks overshadows the imperative for accurate diagnoses. This ultimately compromises patient care and stops endodontists from pursuing the best imaging diagnosis available to help our patients. By emphasizing benefit-risk balance and moving beyond ALARA’s rigid constraints, endodontic practice can optimize patient outcomes while maintaining safety and aligning clinical approaches with contemporary scientific understanding.
References:
Calabrese, E. J. (2015). On the origins of the linear no-threshold (LNT) dogma by means of untruths, artful dodges and blind faith. Environmental Research, 142, 432–442.
Marcus, C. S. (2015). Destroying the Linear No-threshold Basis for Radiation Regulation: A Commentary. Departments of Radiation Oncology, Molecular and Medical Pharmacology (Nuclear Medicine), and Radiological Sciences, The David Geffen School of Medicine of the University of California at Los Angeles.
Oakley P, Harrison DE. ALARA: Evidence against the use of the radiation protection principle as used in the healthcare sector. Diagnostic Imaging Europe. June/July 2020;44:1-50.
Siegel JA, Sacks B, Greenspan BS. There is no evidence to support the linear no threshold model of radiation carcinogenesis. J Nucl Med. 2018;59:1918.
Duncan JR, Lieber MR, Adachi N, Wahl R. Reply: Radiation dose does matter: mechanistic insights into DNA damage and repair support the linear no-threshold model of low-dose radiation health risks. J Nucl Med. January 10, 2019
Dr. Bruno Azevedo is a dual specialist in Endodontics and Oral Maxillofacial Radiology, currently in private practice in Austin, Texas. He has over 21 years of experience utilizing CBCT imaging, with a particular emphasis on Endodontics, and is the author of numerous papers and book chapters on this topic.