Thank you for attending/inviting me to speak. Many of the slides I am about to present are from the American Association of Endodontists’ ENDODONTICS: Colleagues for Excellence program. This program was founded in 1994 with the introduction of the ENDODONTICS newsletter. The topic we will cover today is the use of Cone Beam-Computed Tomography in Endodontics.
Cone beam-computed tomography – or CBCT – is a 3-D radiographic tool for clinical applications in dentistry and endodontics. It enables the clinician to access anatomically accurate 3-D information, identify the possibilities and limitations of treatment, and provides powerful visual information to share with the patient and colleagues.
We care for three-dimensional patients with three-dimensional disease and provide three-dimensional treatment. Shouldn’t we use three-dimensional technology for diagnosis and treatment planning?
One of the benefits of CBCT is the ability to control the field of view and select an optimal field for each patient based on the disease presentation and the region to be imaged. Here, you see a large field of view, which exposes the entire head to radiation. Additionally, the resolution is not as good as a focused field of view scan.
With this medium field of view, both jaws are exposed to radiation. For endodontics, there is no reason to expose more areas to radiation than what we need for the job at hand.
In this focused field of view, a quadrant-sized area is imaged, limiting the patient’s exposure to radiation and providing the clinician with a high resolution image.
For a meaningful comparison of radiation risk, radiation exposures are converted to effective dose, which is measured in Sieverts. The dose to specific tissues is measured, adjusted for the amount of the tissue in the FOV and weighted based on radiation sensitivity of the tissue. In the chart, you can see how CBCT compares to digital radiographs and CAT scans. Doses range from about 5 to about 80 microSieverts, compared to the average annual effective dose from background radiation in the U.S. of about 3,000 microSieverts.
ALARA is the acronym for As Low As Reasonably Achievable and is a fundamental principle for diagnostic radiology. To minimize radiation dose, these steps should be taken: Following appropriate radiograph selection criteria after taking a history from the patient, then clinical evaluation by an appropriate health care professional. Using properly trained and credentialed personnel to make radiographic exposures upon the prescription of a licensed health care professional. Using optimal technique factors including beam projection geometry, beam energy, collimation and filtration. Using the fastest x-ray detector consistent with obtaining a radiographic image of adequate diagnostic quality.
Presently, CBCT is considered a complementary modality for specific applications rather than a replacement for 2-D imaging. According to the joint position statement on CBCT in endodontics issued by the AAE and the American Academy of Oral and Maxillofacial Radiology, clinicians should use CBCT only when the need for imaging cannot be answered adequately by lower dose conventional dental radiography or alternate imaging modalities. You can find the CBCT position statement on the AAE website at www.aae.org/guidelines .
CBCT images are composed of a huge volume of data made up of millions of 3-D voxels. A voxel is the smallest distinguishable box-shaped part of a 3-D image. CT voxels are anisotropic – the height of the voxel depends on the CT beam slice thickness - which limits the accuracy of reconstructed images. With CBCT data, the voxels are isotropic, meaning they are equal in length, height and depth, allowing for geometrically accurate measurements in any plane.
This slide shows the 3 anatomical planes, Transverse, Coronal and Sagittal. Perhaps the most important advantage of CBCT in endodontics is that it demonstrated anatomic features in these three dimensions that intraoral and panoramic images cannot.
CBCT units reconstruct the projection data to provide interrelational images in the three orthogonal planes. The data can be reoriented in its true spatial relationship, and the isotropic nature of the voxels allows image data to be sectioned nonorthogonally to highlight specific anatomic regions for diverse diagnostic tasks. Additional enhancements such as zoom magnification, level adjustments and annotation can also be applied.
In general, the use of CBCT in endodontics should be limited to the assessment and treatment of complex endodontic conditions, such as listed on the slides.
CBCT enables the detection of radiolucent findings before they are visualized on conventional radiographs.
One can certainly appreciate the increased visibility with the CBCT.
Occasionally, apical periodontitis will not penetrate the antral floor, but will displace the periosteum, which will deposit new bone (periapical osteoperiostitis or “halo”). Here you see that it is more difficult on the periapical radiograph to appreciate the apical radiolucency, whereas the CBCT image clearly demonstrates the PA lucency associated with the MB root apex.
A thickened apical PDL space is observed on the PA radiograph.
The CBCT slices reveal a much more distinct and larger apical radiolucency.
The red arrow is pointing to mental foramen. The yellow arrow is pointing to the mixed lesion that is present between the mandibular premolars.
Here, CBCT images of that same case reveal the true size and dimensions of the mixed lesion in all 3 planes.
This periapical radiograph does not fully demonstrate the orientation of the mental foramen nor the inferior alveolar canal’s proximity to the root.
The CBCT images clearly reveal the proximity of the mental foramen to the root apex of that root filled premolar. Should endodontic surgery be considered, it is very important to know the proximity of the root apex to vital structures.
The PA radiograph does not reveal PA radiolucencies associated with the root apices of the mesial and distal roots.
The sagittal view of the CBCT reveal PA radiolucencies associated with both roots, illustrated by the red arrows.
The red arrow on the CBCT axial view clearly shows a missed canal in the distal root.
The upper left picture shows the axial CBCT view of an endodontically treated maxillary molar where there is an untreated MB2 canal, shown by the yellow arrow.
The periapical radiograph of tooth #21 reveals a radiolucency and two canals treated. The yellow arrow on the coronal CBCT slice demonstrates that there is a missed lingual root. Even a second angled periapical radiograph, which would be expected in a case like this, would not afford the same detail about the missed canal as the CBCT does.
The PA radiograph and clinical photo are of teeth #8 and #9 that were traumatized and then splinted. The patient was referred for evaluation and treatment if needed.
The CBCT sagittal slices of teeth #8 and #9 revealed that both teeth had lateral luxations injuries and that there were concommitant aveolar fractures.
PA radiograph of teeth #8 and #9. The patient had a traumatic injury and was then referred for evaluation and treatment. Both central incisors appear to be in their normal positions. Tooth #10 had a complete crown fracture.
The CBCT views revealed that teeth #8, #9 and #11 were out of their alveolar sockets and that there were concommitant alveolar fractures.
The periapical radiograph of tooth #11 reveals an asymetrical widened PDL space suggesting extensive bony involvement, the exact nature of which is not discernable from the periapical radiograph alone.
On the left you see the PA of tooth #11, on the right, the CBCT image clearly shows the lateral luxation with an alveolar fracture.
This image demonstrates a fractured file. Even without a second angled periapical radiograph one can begin to appreciate the tooth structure that has been lost in attempting to remove the fragment.
However, with the CBCT the extent of the strip perforation is now observed
However, beyond the mere incidence of detection, the CBCT shines with its ability to determine the exact location and extent of the resorption which is paramount in determining prognosis and ultimately treatment planning.
Here the periapical radiograph reveals a possible carious or resorptive lesion (red arrows), but it is not as clear as we would like. Given this is the most distal molar in this quadrant, it is a very strategic tooth which demands accurate diagnosis and treatment planning.
The CBCT views clearly reveals extensive resorptive defects. Unfortunately, this tooth was deemed to be non-salvageable.
While conventional intraoral radiography provides clinicians with cost-effective, high-resolution imaging that continues to be the front-line method for dental imaging, is it clear that there are many specific situations where the 3-D images provided by CBCT facilitate diagnosis and treatment. CBCT is a valuable task-specific imaging modality, producing minimal radiation exposure to the patient and providing maximum information to the clinician.
I hope that I have provided you with some valuable information on the use of CBCT in endodontics. Thank you for inviting me to speak to your group. If you have further questions, I’ll be happy to talk with you after the meeting, and I do have (extra copies of the newsletter, business cards, referral slips, etc.) for anyone who is interested in more information. Thank you for your time and attention. You’ve been a wonderful audience.
Cone beam computedtomography
Cone Beam-ComputedTomography and Endodontics
Principles of CBCT - What is it?Anatomically accurate 3-DinformationBetter understanding of “thepatient” as opposed to “thetooth”Identify possibilities andlimitations of treatmentPowerful communication withpatients and colleagues
ALARA PrincipleFollowing appropriate radiograph selectioncriteriaUsing properly trained and credentialedpersonnelUsing optimal technique factorsUsing the fastest x-ray detector
Judicious Use of CBCTClinicians should use CBCT only when the needfor imaging cannot be answered adequately bylower dose radiography.
Principles of CBCT - Voxel Imaging Area Voxel (VOlume piXEL) is 50 mm the smallest building block of a 3-D image 38 . mm Simulated bone defects in acrylic blocks and the human mandible proved . 076m .076 m that CBCT is an accurate mm . Cubic Voxel way to measure osseous 076m m lesion and volume
Advantages of CBCT Transverse or Axial Coronal Sagittal
Potential Endodontic Applications of CBCT Differentiation of pathosis from normal anatomy Relationships with important anatomical structures Management of aberrant anatomy (i.e. Dens, C- shapes) External and internal resorption defects Diagnosis of root perforations Identification of missed canals, additional anatomy Management of fractured instruments
Potential Endodontic Applications of CBCTAiding surgical planningRetreatments- treatment planningTraumatic injuries - diagnosis and treatmentplanningIntra-operative (i.e. finding canals)Maxillary sinusitis of dental originCalcified casesFacial pain cases to rule out odontogenicetiology
Detection of Apical PeriodontitisCBCT is significantly more sensitive thanconventional x-rays for demonstrating‘AP’ Estrela C et al, JOE 2009 Cotton TP et al, JOE 2007 Lofthag-Hansen S et al, OOOE 2007
CBCT: What Are We Missing? CBCT showed significantly more lesions (34%, p< . 001) than PA’sLow KMT, et al,JOE 2008