On CBCT Scans in Endodontics

Rico Short, DMD


Everyone wants to have the latest gadget, and, nowadays, it seems many are willing to pay a premium to have it. Think of the iPhone X with face recognition, but priced at more than $1,000, is it really necessary? Dentists are no exception. Take, for example, cone beam computed tomography (CBCT) scanners. The technology has an average price tag of about $60,000 to $90,000. Granted, it is one of the most significant advances in dentistry in the last decade; however, is it really necessary for all clinicians?

CBCT Use in Endodontics: The Standard of Care?
There are some clinicians preaching that “CBCT is the standard of care.” However, the truth is CBCT is not currently the standard of care. Remember when, more than 20 years ago, the surgical microscope was the “next big thing” in endodontics? Even with the advancement of the surgical microscope in helping endodontists locate calcified canals, remove separated instruments, repair perforations, and aid in microsurgical procedures to save teeth, it is still not the standard of care. The judicial system defines the standard of care as “that which a reasonable healthcare provider would, or should do, under similar circumstances.”1

In 2008, when the economy nosedived, endodontists started to panic. Root canal therapy started to slow down, and many patients decided to have extractions instead. I was at a practice management seminar, and a well-known lecturer said, “As an endodontist, if you don’t learn how to place implants, you will be out of practice within 2 years.” This practice management “guru,” as well as various other dental organizations, started to push clinicians to do implants to save their practices. We have seen that wave come up to the shore and then wash back out. The majority of endodontists are now still performing more root canal therapies than placing implants. Root canal therapy is in our wheelhouse; it is what we do best as endodontists!

Endodontists Pressured to Purchase CBCT Machines?
Fast-forward 10 years, and we now find that the pressure is on for all endodontists to have a CBCT machine in their offices. There are some GPs that will not refer patients to an endodontist if they don’t have a CBCT machine. In addition, there are endodontists who are scanning every patient before any endodontic procedure while, of course, charging the patient to pay for the machine and to make a profit from its use. So how did we get here? Are marketing dollars from CBCT manufacturers pouring into the dental schools, research programs, and lecture circuits and enticing the various foundations with generous donations? I don’t know the cause, but I see the effect. In the end, it’s the patient who gets the raw deal if a CBCT scan is really not necessary, which also can result in a lawsuit. Whether or not you have a CBCT scanner in your office does not define the caliber of clinician you may be. Scans can be ordered at mobile scan units, via oral surgery offices, and even in some hospitals and private health clinics. The million-dollar question is, “What’s the main objective or reason for ordering a scan?”

Interpreting the Scan
CBCT has some powerful uses in dentistry, such as diagnosis, surgical planning, implant treatment planning, etc, but it can also be quite limited for use in some areas in dentistry. In particular, the image resolution still can’t pick up micro-cracks or small vertical root fractures that are the Achilles’ heel in root canal therapy when deciding between trying to save a tooth with a root canal or do an extraction.

It is also important to note for any dentist or specialist who acquires a CBCT scan that the clinician must know how to properly read and interpret the scan. So, who is responsible for the interpretation and legal responsibilities regarding any incidental findings? According to Dr. Bruno Azevedo,2 a board-certified oral and maxillofacial radiologist, the clinician who acquires or interacts with the CBCT volume (even if acquired in another practice or imaging center) is responsible for the interpretation of it. Furthermore, as an example, some endodontists are under the misconception that they are only responsible for the endodontic interpretation of the volume. Whatever data is captured in that image, it is the clinician who is responsible for interpreting and properly documenting the scan and explaining any findings to the patient. Also, any clinician who performs a CBCT on a patient is held to the same standard of care as a board-certified radiologist, regardless of the intent of the exam, in the same way as a GP performing a root canal is held at the same level as a specialist in endodontics.

Azevedo2 also states that proper documentation of artifacts while using CBCT imaging is also important. Artifacts such as beam hardening and streaking may compromise an accurate interpretation of the scan. If assistance is needed to interpret the scan, it is highly recommended that the scan be sent to a board-certified radiologist.

There are more than 50 CBCT scanners on the market, and the numbers are growing. According to the European Society of Endodontology, these scanners have variations with regard to their specifications, exposure settings, effective dosages, and image quality. Furthermore, the committee found the diagnostic yield changes based on the type of scanner. This can keep the results from a specific CBCT scanner from being able to be interpreted by a different CBCT scanner due to different software. Based on this data alone, how can we standardize a CBCT scan or label it as a standard of care using various machines with various software? Before a CBCT machine is purchased and used on patients, the clinician must have core knowledge of CBCT radiography before requesting CBCT scans and must also regularly update his or her knowledge. A comprehensive discussion must take place between the clinician and patient, and only then is the patient’s consent to undergo a CBCT procedure valid.

Advantages in Appropriate Use of CBCT Scans
Most clinicians agree that it is advantageous to take a CBCT scan before dental surgery in many cases. This can help avoid iatrogenic injuries involving anatomical structures, such as the maxillary sinus cavities, inferior alveolar nerve, and so on. CBCT scans can help reveal extra root canal anatomy, traumatic fractures, missed canals, resorptions, and perforations and help the clinician get properly oriented during treatment complications. CBCT scans have been shown to locate significantly more canals in root-filled teeth than periapicals alone.3 However, scans should not be used as a screening tool to look for canals or to compensate for subpar diagnostic or clinical skills.

In addition, CBCT images reveal up to 40% more previously undetectable lesions. The question is, what do we do now that we are capable of finding so many lesions and, notably, often asymptomatic ones? Do we retreat? Do we do apical surgery? Do we watch the lesion and take a scan every 6 months? Does that mean there will be a 40% increase in the number of endodontic procedures done as well? One study found that vital teeth vary in PDL width anywhere from 0.2 to 1 mm.4 Could it be related to occlusion vs pulpal pathology? Are we liable for not treating, or overtreating, teeth with lesions found on a CBCT scan and not on a 2-D radiograph?

Limitations of CBCT Scans
CBCT scans can give us volumes of information preoperatively and during treatment, but what are some of the limitations? A significant problem is that the images produced do not have high resolution, especially around root-filled teeth or teeth with metal posts and crowns.5 Scatter and beam hardening continue to be a challenge compared to 2-D radiographs. If this scattering and beam hardening is within, or close to, the tooth being assessed, the resulting CBCT images will be of minimal diagnostic use.6

Diagnosis of Vertical Root Fractures
One study showed that CBCT scans cannot reliably detect small cracks (micro-cracks) or incomplete vertical root fractures. They would have to be surgically flapped and viewed under the surgical microscope for confirmation. Larger fractures (macro-cracks) are likely to be found clinically or on a periapical and possible bite-wing radiograph, in which case a CBCT scan would be contraindicated.7 In addition, another study found that CBCT is unreliable in detecting vertical root fractures in root-filled teeth. This is due to the image scatter or beam hardening produced by the root canal filling material. This will mask the area of the root required to be evaluated.8

Detection of Canal Calcification
Canal sclerosis, or calcification, is a common challenge in adequately disinfecting canals. Studies show that a CBCT scan may be of minimal benefit in assisting with the location of the canal as the resolution is significantly worse than that of a periapical radiograph. Therefore, if conventional radiography does not reveal a canal, it would unlikely be visible with a CBCT scan. In addition, a recent study (Journal of Endodontics, 2017) demonstrated that CBCT scans are not effective in locating the MB2 canals of maxillary molars compared to direct access.

The use of CBCT is rapidly expanding in dentistry among all clinicians. Should all clinicians have CBCT scanners readily accessible in their offices? It depends on the clinician and the scope of his or her practice. This topic has caused great debate among endodontists. We must keep in mind that ionizing radiation is being used, and, therefore, our patients should be exposed to it as little as possible. Each case must be evaluated thoroughly before deciding to take a CBCT scan. Above all, this procedure should always be in the best interest of the patient.

So, before you purchase a CBCT scanner just so you can be up to date—or maybe to impress your dental colleagues, patients, and/or referring dentists if you are a specialist—be certain to learn about and understand CBCT technology and seek proper training in its use. If you are not thoroughly trained in the interpretation of CBCT scans, then send the image(s) to a board-certified oral maxillofacial radiologist for an accurate and thorough diagnosis/diagnoses and to avoid any potential misdiagnosis/misdiagnoses, which can sometimes lead to serious legal problems. This is only fair to the patient who is paying for this diagnostic service.

1. Curley AW. Dentistry, the law, and CBCT. October 26, 2016. http://www.dentaleconomics.com/articles/print/volume-106/issue-10/science-tech/dentistry-the-law-and-cbct.html. Accessed June 2, 2018.
2. Azevedo B. Cone beam CT interpretation: With great power comes great responsibility. October 25, 2017. https://www.aae.org/specialty/2017/10/25/cone-beam-ct-interpretation/. Accessed June 2, 2018.
3. Davies A, Mannocci F, Mitchell P, et al. The detection of periapical pathoses in root filled teeth using single and parallax periapical radiographs versus cone beam computed tomography—a clinical study. Int Endod J. 2015;48:582-592.
4. Pope O, Sathorn C, Parashos P. A comparative investigation of cone-beam computed tomography and periapical radiography in the diagnosis of a healthy periapex. J Endod. 2014;40:360-365.
5. Mora MA, Mol A, Tyndall DA, et al. In vitro assessment of local computed tomography for the detection of longitudinal tooth fractures. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2007;103:825-829.
6. Estrela C, Bueno MR, Leles CR, et al. Accuracy of cone beam computed tomography and panoramic and periapical radiography for detection of apical periodontitis. J Endod. 2008;34:273-279.
7. Chang E, Lam E, Shah P, et al. Cone-beam computed tomography for detecting vertical root fractures in endodontically treated teeth: a systematic review. J Endod. 2016;42:177-185.
8. Patel S, Brady E, Wilson R, et al. The detection of vertical root fractures in root filled teeth with periapical radiographs and CBCT scans. Int Endod J. 2013;46:1140-1152.

Dr. Short received his DMD degree from the Medical College of Georgia School of Dentistry in 1999. In 2002, he earned his postdoctorate degree in endodontics from Nova Southeastern University, and, in 2009, he became a Diplomate of the American Board of Endodontics. His private practice, Apex Endodontics PC, opened in 2004 and is located in Smyrna, Ga. He can be reached via email at dr.short@yahoo.com or at apexendodontics.net.

Disclosure: Dr. Short reports no disclosures.

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