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«To CT or not to CT»: that is the question

Автор: Dr. Terrel F. Pannkuk, DDS, MScD, AMED Vice President Diplomate of the American Board of Endodontics

Статья опубликована в журнале AMED Vision SPRING/SUMMER 2010 | VOL 6 ISSUE 2

All new technology creates fervor and scampering amongst those wanting to be first. The “earliest” adopters are the risk takers willing to beta test and weather the frustrations of misapplication, unforeseen complexities, and adverse results. The “early” adopters are not the first but closely pay attention to the first group eagerly observing their experiences and will selectively embrace a technology as soon as a definitive advantage is seen without delay.

Which group are you? We need both. How would a battle be won if all soldiers wanted to be in the second line watching the first willing to charge into a line of fire?

Cone Beam Computed Tomography will undoubtedly revolutionize dental diagnosis in the near future; as a matter of fact it already has!

I purchased a CT machine in order to improve my diagnostic capabilities and not be left behind the technology curve, knowing that there are many cases where it can provide very useful information helping to validate a selected treatment option and determine prognosis. Incorporating this technology into my practice necessitated an application protocol. Do I discriminate and select which patients should have a CBCT or do I raise my consultation fee for all patients and scan all patients like they are boarding a fight at the airport?

I reconciled this dilemma “to CT, or not to CT” by assessing the patient’s “COD” or critical option determinant (not meaning cash on delivery). Critical thinking is the essence of diagnosis and treatment planning, these high tech tools are certainly necessary but still just an ancillary tool relative to appropriate clinical judgment. In the same way one takes only conventional radiographs that are needed, it certainly shouldn’t be any different with the CT. The radiation is not the issue as much as effort, energy and cost of buying a machine, reading the scans, sending the reports, and mailing CD disks. The latest microCT machines with limited fields of view expose the patient to very little radiation equivalent to two to three periapical radiographs.

An experienced, trained endodontist utilizing a microscope will rarely miss additional root canal systems by troughing grooves and microscopically exploring deep anatomy. A microCT has the resolution to show some large lateral canals and some additional anatomy, but not currently at the desired resolution to see “everything” including fine incomplete root fractures. Microscopic exploration is still required in most cases. The unique advantage of a CT scan is the three-dimensional perspective gained on equivocal cases where pulp vitality is questionable (Figure 1), cases with resorption (Figure 2), and suspected teeth with fracture having periodontal bone loss (Figure 3). There are some other important rare applications for the diagnostic CT (Figure 4).

Each individual clinician should use their own judgment in deciding when to prescribe a scan based on the specific unique case and the value of the information it will provide them in diagnosis, treatment planning, or even during the execution of treatment. The following is simply an example of my personalized clinical protocol:

1. Trauma cases – most all cases to find evidence of resorption, root fracture, or fracture of the alveolus.

2. Root resorption – only if the possibility of treatment is being considered, or if adjacent teeth are being considered for evaluation and identification of multiple resorption foci.

3. Endodontic/ periodontal/ oral surgery – most all cases should be scanned to identify vital structures and osseous topography.

4. Symptomatic patient when the periapical radiograph reveals no pathosis and the clinical testing is equivocal (endodontic treatment) – when during an endodontic exam, pulp vitality is uncertain and the differential diagnosis includes some entities determined by osseous destruction that could be identified on a CBCT scan.

5. Complex anatomy (endodontic treatment) – if “exotic” anatomy is expected then a CBCT might be warranted prior to treatment, a CBCT can always be taken before, during, or after endodontic treatment to insure all anatomy has been addressed. It is helpful to take the scan after endodontic obturation if unusual root canal anatomy is found highlighted by radiopaque filling (Figure 5).

6. Calcified Cases (endodontic treatment) – complete pulp canal obliteration is rare but when it prevents negotiation, a CBCT can be invaluable.

7. Facial Pain – cases to rule out odontogenic etiology, (only if an osteolytic or radiolucent entity is part of the differential diagnosis).

8. Suspected vertical root fracture cases – if a narrow sulcular defect doesn’t already condemn the tooth and there is some useful diagnostic determinant like a banded lesion seen on saggital, or a hemispherical radiolucency seen while sliding down an axial plane that would aid in prognosis assessment or treatment planning. If a patient isn’t willing to accept the risks of treating a tooth having a deep sulcular defect with the “best case etiology”, then taking a CT provides no COD; the patient would reject both a guarded and a hopeless case.

9. Endo-Perio Cases – only if taking a scan provides a COD. If the patient is not willing to accept treatment of a guarded or hopeless prognosis case, then there is no value in taking a CBCT to find out the pattern of an already broken down periodontium whether it is endo-perio, or perio-endo). (Figure 6)

10. Maxillary Sinus involvement, only if is there a possible odontogenic consideration; if the teeth in the entire sextant are cleared as being vital/healthy and a nondental sinus path entity is suspected, the patient should be sent to the ENT for the scan and not have a CBCT taken by the dentist.


Figure 1. Equivocal pulp testing on a mandibular first molar through a porcelain crown failed to provide sufficient evidence to diagnose a necrotic pulp. The periapical radiograph demonstrated a diffuse periapical radiolucency which was shown to be clear periapical osseous destruction circumscribing the distal root apex. The entire sextant are cleared as being vital/healthy and a nondental sinus path entity is suspected.
Figure 2. A large internal resorption defect was identified in the palatal root of the maxillary first molar. Although faintly visible on the periapical radiograph; it’s dimensions can be more accurately mapped with a CBCT scan allowing a better assessment of prognosis.
Figure 3. A bone loss pattern suspected to have a fracture etiology shows limited osseous destruction to the middle level of the distal root.
Figure 4. The CBCT allowed three-dimensional mapping of multiple pin-build-ups identifying those perforating the root and exposing pulps.
Figure 5. CBCT taken after endodontic obturation of complex anatomy.

Figure 6. Primary lingual periodontal defect developed after orthognathic surgery. The scan revealed the associated bone loss and the proximity of the hardware to the mandibular nerve canal.

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