As a general dentist (GP), anatomy can occasionally throw you for a loop. We see thousands and thousands of people every year. Sometimes their anatomy falls into the “norm,” and sometimes it doesn’t. Being an experienced clinician can help you navigate these differentiations. However, today’s advanced technology also can take the “experience factor” out of your hands. When treating patients with anatomic anomalies, clinicians can use this technology to better serve these patients.
I have had a ProMax Pro Touch 3-D Classic CBCT (Planmeca) machine since December 2015. Not only do I use its 3-D capability to plan my implant cases, but I also use it for any endodontic case I plan to do, even the simpler ones. The 3-D volumes for endodontic cases allow me to find extra canals, like the MB2 canal and the 2 distal canals, or that third middle mesial canal on lower molars that may be missed during canal opening and cleaning. Pulp stones and hairline fractures also can be seen so that these teeth can be restored properly.
Sometimes the “simple” cases turn out to be not so simple. I cannot tell you how many times I’ve opened a tooth and have come across unusual anatomy that made me sweat a little and say a few prayers as I negotiated it. Using the CBCT 3-D technology to my advantage, I can see exactly what this tooth has in store for me. And, being a GP, I have the luxury of either proceeding with treatment or referring the patient to my local endodontist—so he can sweat a little too!
Using CBCT 3-D Scans in Endodontics
The Planmeca ProMax Pro Touch 3-D Classic machine can take an ultra-low-dose CBCT 3-D scan of a 50- x 50-mm to an 80- x 80-mm field of vision (FOV). For a patient who needs endodontic treatment, we can narrow the FOV to the smallest size of 50 x 50 mm using an ultra-low dose of radiation while maintaining diagnostic imaging quality. This usually gives you at least 3 teeth in the region you want to see, depending on the size of the patient and whether we’re looking at a posterior tooth or an anterior tooth.
Hundreds of 2-D radiographs are taken during the 3-D process, and the Romexis software uses these files to create a 3-D volume set of data. We can use all 3 planes (axial, sagittal, and coronal) to determine the anatomy of the tooth that we will be treating endodontically.
The axial plane is the occlusal view. We can move the cursor up and down to trace the canals, from the coronal portion of the tooth all the way to the apex. This view can help you visualize what the pulpal chamber and floor will look like once you open up the tooth. Here you can find extra canal openings: separate ones at the pulpal floor, as found in Case 1 (at right), and canals that split off from the main one, as found in Case 2 (p. 115). It can also help with fractures and resorption in the roots as well as curves that may be difficult to negotiate.
The sagittal plane shows the cross section of the buccal and lingual view, looking from either the mesial or distal of the tooth in question. This view can help to determine the number of canals, fractured roots, and curves in the roots.
The coronal plane shows the buccal and lingual views of the tooth, similar to our normal 2-D periapical view. I usually use this view to measure the length of the roots and the depth of the pulp chamber so I know where the openings of the canals are located.
If the roots are curved, calcified, or have large pulp stones in the chamber, I often refer these patients to the endodontist. Sometimes you can miss one of these factors in a regular 2-D periapical. I hate to open a tooth only to find that I am unable to finish it. Using 3-D technology can give you a better picture of the tooth anatomy so all aspects of the tooth can be seen. In this way, the clinician can determine the best course of action before any clinical work is begun. It’s a time saver for both me and my patients.
Diagnosis and Treatment Planning
A 43-year-old male came to the office with a toothache on his maxillary left side. He knew that he had a broken tooth and wanted to know how to treat it. A periapical (PA) radiograph was taken to see the extent of the decay (Figure 1). It revealed periapical pathology at the apex of tooth No. 12.
The treatment options for this case were discussed with the patient to treat his irreversible pulpitis. The patient wanted to save the tooth with endodontic therapy and a post/core and crown instead of doing an extraction and implant or a removable prosthesis or bridge. The roots looked thin, so a ProMax 3-D CBCT scan was taken to see the anatomy of the roots in detail. The 3-D view showed 2 buccal canals and one lingual canal (Figures 2 and 3). It was determined that the canals, even though they were thin, could be found. There was no calcification, and it was determined that the canals could be negotiated and obturated.
For this case, we began the process of endodontic treatment by anesthetizing the tooth with buccal infiltration using 2% Lidocaine (1:100,000 epinephrine) and 3% Mepivacaine (no epinephrine). A second round of anesthesia was done utilizing a Peri-Press Injector in the PDL space using 4% Articaine (1:100,000 epinephrine). The decay was then removed. Caries indicating solution was used to confirm complete removal.
Next, the pulp chamber was accessed, and the canals were found and negotiated with K-files sizes Nos. 10 to 20. Initial debris was removed using an ultrasonic handpiece, and the canals were negotiated to their apex/working length with a No. 20 K file using the M-4 handpiece. The J. Morita USA Root ZX Apex Locator confirmed apex length.
The rubber dam and clamp were placed, and the sequence of TF Twisted Files (Kerr Endodontics) was then used to shape the canals. We started with a .08 taper No. 25 file, moved onto a .06 taper No. 25 file, and ended with a .06 taper No. 30 file. Each file was followed with a bath of full-strength sodium hypochlorite. Nos. 20 and 25 gutta-percha points were placed to length, and a periapical film was taken for confirmation of length and fill (Figure 4). The gutta-percha was removed, and all canals were flushed with sodium hypochlorite.
QMix 2in1 (Dentsply Sirona Endodontics) irrigation solution was used to remove the smear layer and to accomplish the final disinfection of the canals. An EndoActivator (Dentsply Sirona Endodontics) was used to agitate the QMix 2in1 for 60 seconds in each canal. Paper points were then used to dry the canals. Canal sealer (Tubli-Seal Root [Kerr Endodontics]) was placed in each canal, and the gutta-percha points were placed and sealed at the pulp chamber. A cotton pellet and intermediate restorative material (IRM) were placed until the post and core and full-coverage restoration could be done. A final PA radiograph was taken (Figure 5).
Diagnosis and Treatment Planning
A 17-year-old male came to the office with a toothache in tooth No. 21. The PA radiograph revealed pathology at the apex (Figure 6). The tooth had been previously filled with a small occlusal composite. This young man had large pulp chambers, so the filling was near the pulp. The angle of this PA radiograph showed a split canal. A CBCT volume was taken, confirming that the tooth had a single root with a single canal that split into 2 (buccal and lingual) canals in the apical third (Figures 7 and 8).
The same endodontic procedure described previously was done to clean, shape, and obturate the canals (Figure 9). A confirmation CBCT was then taken after obturation to make sure that the canals were properly filled (Figure 10). A composite filling was placed as the final restoration due to the small hole that had been created to gain access.
According to a 2009 study1, 64% of 400 maxillary premolars that were examined had 3 separate roots. That’s a majority of teeth found with 3 separate roots in this study! Visualization can be difficult with these thin roots on a 2-D radiograph, even if you get a good periapical angle. In a 2013 review2, 17 studies compared the number of canals at the apex of 3,384 mandibular premolars. Only 11% of these mandibular premolars had 2 or more canals at the apex. It’s good for a GP to know these statistics because this information can assist in determining if these cases should be referred to the endodontist as well as the likelihood of finding an extra root/canal.
Difficult cases may need to be referred to a specialist, but they can sometimes be made easier with the help of CBCT 3-D technology. These teeth would likely have been difficult for a GP who was unable to do a CBCT. The cases presented here were successful because this technology made proper and detailed planning possible.
Most patients want to have all their procedures done by their own GP, and this technology will help your patients as well as your bottom line. In the past year and a half, I have found that it was worth the investment. The addition of proven technologies, such as CBCT, can be of great benefit to both clinicians and their patients.
- Arisu HD, Alacam T. Diagnosis and treatment of three-rooted maxillary premolars. Eur J Dent. 2009;3:62-66.
- Jha P, Nikhil V, Arora V, et al. The root and root canal morphology of the human mandibular premolars: a literature review. Journal of Restorative Dentistry. 2013;1:3-10.
Dr. Aldrich is a practicing general dentist in Fairlawn, Ohio. She graduated from the Case Western University School of Dental Medicine in 1999. She is a Fellow of the AGD as well as the International Congress of Oral Implantologists. She can be reached via email at firstname.lastname@example.org.
Disclosure: Dr. Aldrich reports no disclosures.