Orthodontic imaging: The future is now

The special article, “Clinical considerations and potential liability associated with the use of ionizing radiation in orthodontics” (Abdelkarim A, Jerrold L. Am J Orthod Dentofacial Orthop 2018;154:15-25), provides a considerable amount of information regarding the risks, benefits, imaging selection criteria, and timing (before, progress, final) of radiographic imaging in orthodontics. The advantages and limitations of various imaging techniques are discussed in detail. The references are numerous, and “the process of prescribing radiographs in orthodontics” is summed up succinctly as being “based on the practitioner’s clinical judgment for a particular patient’s presentation, and the ALARA directive—keeping radiation as low as reasonably achievable.”

In discussing “initial radiographic acquisition in orthodontics,” the authors stated that “the combination of pretreatment panoramic and cephalometric radiographs appears to be appropriate and sufficient in most cases.” There is also a lengthy discussion regarding the use of CBCT imaging, with the authors stating that “although the benefits of CBCT in orthodontics cannot be ignored, the orthodontist must be able to justify that CBCT images bring a benefit to the patient over what can be obtained via 2D imaging.” This need for justification appears to be related to the assertation that “for most CBCT examinations, the effective radiation doses are greater than those for conventional radiographic techniques.” How then would the authors’ recommendations regarding CBCT change if a practitioner chose to use CBCT scans for all radiographic acquisitions with effective radiation doses equal to or less than those for conventional 2D radiographic techniques?

In late 2013, the current generation of CBCT scanners—the so called “ultralow dose scanners” (ULD)—became available in the dental marketplace in the United States. By limiting the field of view (FOV) and managing voxel size and scan time (ULD settings), the dentition can be imaged in 3 dimensions at an effective dose of 5.3 μSv. A larger FOV (16 × 13 cm) additionally capable of producing reformatted panoramic and cephalometric views (lateral and anteroposterior views for most patients) has an effective dose of 11.4 μSv. These effective dose levels compare favorably with, and in many cases are less than, the 2D panoramic and cephalometric effective doses noted in the article’s Table I. Also, in Table I, the authors provided effective doses for CBCT imaging. The CBCT imaging effective dose range stated is 20 to 1025 μSv. The low-end effective dose stated in the Table is not accurate when current generation CBCT scanners are used with ULD parameters. When considering the effective dose of other 2D imaging options, particularly if ectopic teeth are suspected, ULD CBCT should be considered the imaging option of choice.

There are important considerations when CBCT imaging is used in orthodontic practice, and the authors have reviewed many of these in detail. I would like to add a few more points.

  • 1.

    CBCT scanners are versatile, allowing the practitioner to select a specific FOV and resolution for each patient’s diagnostic needs. Simplistically, smaller FOVs and ULD settings expose the patient to lower effective doses. Larger FOVs and higher resolution settings can significantly increase effective doses. Regarding these selectable parameters, the ALARA and the ALADA (as low as diagnostically acceptable) concepts must be adhered to. Orthodontic radiographic acquisition using ULD CBCT scanning protocols adheres to both principles.

  • 2.

    Older CBCT scanners manufactured before the introduction of ULD CBCT technology (pre-2013) typically cannot acquire similar FOV images at effective dose levels that are less than those of 2D digital panoramic or cephalometric technology. Risk and benefit factors (ALARA) must be considered when using older CBCT scanners (also an important consideration with older 2D imaging technology). When researching the use of CBCT technology in orthodontics, it must also be understood that any articles published in, or before late, 2013 (or citing references before 2013) evaluated CBCT scanners manufactured before the availability of ULD scanning protocols. Many recommendations for CBCT scanning in orthodontics in the older literature are based on higher effective dose exposures and the ALARA (risk/benefit) directive. The American Dental Association’s Council on Scientific Affairs advisory statement on “The use of cone beam computed tomography in dentistry (American Dental Association Council on Scientific Affairs. J Am Dent Assoc 2012;143:899-902)” and the American Academy of Oral and Maxillofacial Radiology’s “Clinical recommendations regarding use of CBCT in orthodontics. Position statement by the American Academy of Oral and Maxillofacial Radiology” (this position statement is now deemed invalid, as is has not been re-approved in the 5 year period since first published) (American Academy of Oral and Maxillofacial Radiology. Clinical recommendations regarding use of cone beam computed tomography in orthodontics. [corrected]. Position statement by the American Academy of Oral and Maxillofacial Radiology. Oral Surg Oral Med Oral Pathol Oral Radiol 2013;116:238-257) are 2 such publications. Updated studies with recommendations based on the use of ULD CBCT technology vs 2D radiographic techniques would be beneficial.

  • 3.

    CBCT scans with lower effective doses (ULD) inherently have lower resolution and thus lower image quality than higher resolution scans. Although high-resolution scans may be required for certain periodontic, endodontic, or oral surgical procedures, the quality of ULD CBCT scans is diagnostically acceptable for orthodontic purposes (ALADA) and is improving as the technology advances.

  • 4.

    Concerns over the interpretation of CBCT scans taken for orthodontic diagnostic purposes continue, and the authors have reviewed these in detail. The interpretation of intraoral radiographs has been included in dental school curricula for more than half a century. Today, the interpretation of digital 2D intraoral and panoramic radiographs is taught in dental school. The interpretation and analysis of cephalometric radiographs (lateral and anteroposterior) are taught in our orthodontic residencies. At the 2017 American Association of Orthodontists’ Winter Conference in Fort Lauderdale, Chris Bentson reported on a survey of recent (2016) orthodontic residency graduates in the United States: 88% responded that they had used CBCT imaging for diagnosis and treatment planning during their residencies. In my opinion, as ULD CBCT imaging becomes more common in orthodontics, just as it has become more common in orthodontic residency programs, the interpretation and analysis of CBCT scans must become part of orthodontic residency curricula. The availability of continuing education courses on this subject must also increase. Dental education has evolved with advances in technology, and the education in our specialty must evolve as well.

The authors’ conclusions are well thought out and concise. I agree with them fully, with 1 exception. “4. Consider CBCT imaging only when it is expected to yield a benefit to the patient or change the outcome of treatment over 2D radiographs.” When exposure protocols (FOV, voxel size, scan time) are tailored to diagnostic needs, the current generation of ULD CBCT scanners can provide an immediate benefit—more diagnostic information with an effective dose equal to or less than 2D radiographs. My conclusion would be that CBCT imaging is acceptable for radiographic acquisition when its effective dose is less than or equal to comparable FOV 2D radiographs, or when it is expected to yield a benefit to the patient or change the outcome of treatment over 2D radiographs.

The viewpoints expressed are solely those of the author(s) and do not reflect those of the editor(s), publisher(s), or Association.

The author completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest, and none were reported.

Only gold members can continue reading. Log In or Register to continue

Dec 8, 2018 | Posted by in Orthodontics | Comments Off on Orthodontic imaging: The future is now
Premium Wordpress Themes by UFO Themes