One of the most common challenges when performing endodontic treatment is negotiating a calcified canal. In this instructional submission some very valuable tips and suggestions will be presented to help with pulp canal obliteration.
Critical thinking is essential when performing a healthcare service. A systematic approach beginning with understanding the treatment objectives develops the foundation for a successful outcome that best serves the patient. The following steps will guide you through your initial conceptual understanding of the treatment goal, into the logical steps of procedural execution, and finally to the transformation of the case from a difficult challenge to a standard set-up for simple later completion:
The goal of treatment is to eliminate endodontic disease and protect the attachment apparatus. If the diseased dentin substrate is left behind there is the potential for recurrent disease or in the case of an anterior natural tooth, continued unaesthetic staining. In spite of the current trend toward minimizing root canal preparation, removing all tertiary “irritational” dentin makes sense because it is diseased dentin that has been formed through unnatural pathogenesis. Why would one think leaving pathogenic material offers a significant benefit to the patient? Secondary dentin formation from natural aging is different and unnecessarily removing all dentin formed after apex closure on a heavily restored, aged, weakened root might be a bit extreme. The recommendation is not to be “overly” concerned with preservation of secondary and tertiary dentin to the point that it impedes the objectives of definitive endodontic therapy.
The clinician must have a clear understanding and perspective of the root anatomy. This means multiple angled traditional radiographs (horizontal/bitewing, straight periapical, and slight off-angle) are required along with a CBCT scan in some cases. In the two maxillary anterior teeth presented in this submission a CBCT scan was judged to be unnecessary (Figures 1, 2, 3, and 4). A new budding technology of dynamic navigation will undoubtedly play a role in the future management of these cases but at the time of writing this submission the QR coded templates and necessary attachments on the handpieces are quite large and cumbersome, making the ergonomics and isolation with a rubber dam unusually difficult so that treatment in difficult access posterior areas of the jaw impossible without unreasonable treatment compromises. That will change as the technology becomes more compact and ergonomic in the future. It is very important to judge every new technological gadget with critical assessment assessing whether it is ready for “prime time”. This author owns a dynamic navigation device which is very suitable and helpful for implant placement but not judged ready for use in endodontics. For now, mental imaging of root anatomy and traditional radiographic data remain a staple of successful endodontic practice.
The placement of the rubber dam can greatly aid visual orientation of the root long axis. For single rooted maxillary anterior teeth, the canal tends to be centered in a predictable location. Securing a double-winged butterfly clamp as deep onto the root as possible lines up the two “beaks” so that a mental imaginary line drawn bisecting them will with near certainty intersect the center root and the pulp chamber location in the mesiodistal dimension. This simplifies the search to the labiolingual dimension (Figures 5, 6, and 7).
The initial penetration point should be just above the lingual cingulum which will be favoring the lingual direction a bit more than the labial knowing the crown will be angled at a more buccal position requiring a lingual starting point to keep on path to the root canal. Sweep the access prep coronally forming a triangle so that good visibility of the darker dentin representing the calcified pulp chamber can be achieved. If the tooth does not have a restoration and will require bleaching it is important to at least remove the discolored tertiary dentine harboring dark staining inclusions. A prudent decision to be conservative has to be made if the pulp horns are extremely high and angled toward the incisal. Dr. Herbert Schilder described “two triangles” that need to be removed when treating anterior teeth so that direct line access and convenience form can be achieved to adequately clean and shape the root canal system (Figure 8).
Apical penetration a few millimeters from the coronal entry point will start to show the dark dentin area of the calcified pulp chamber (Figure 9). A striated ‘star-burst” outline exists on the periphery of the calcified. This additional feature helps validate the calcified canal position (Figure 10).
The next step is to penetrate just lingual to the dark calcified dentin in the “starburst” area with a small microbur like the Munce bur (Figure 11). This helps guide you toward the center of the root as you proceed apically. You may, or may not, see a white dot in the center of the dark dentin that represents patent canal space filled with debris. You can highlight the white dot by rinsing with alcohol and drying to frost it. Wetting the prep with 17% EDTA will help maintain the color contrast of the peripheral primary dentin and secondary/tertiary darker dentin.
The small bur penetration will cause you to lose your visual reference if you go to deep too quickly. Continue with approximately 1mm increments. After each small bur penetration follow with a larger diameter round carbide bur, starting with a #4 (Figure 12). This will re-establish a wider flat smooth surface so you can continually identify the calcified canal area. Keep moving the prep slightly toward the lingual of the dark area. When you get to the cervical level switch to a #2 carbide which will be the approximate diameter of the dark calcified canal as you proceed apically (Figures 13 and 14).
The white dot will consistently become present and easily identified as you move into the cervical root. It may, or may, not become negotiable with a small precurved K-file. Keep rinsing with 17% EDTA to clear debris. Alternately frost with alcohol if you need to find the white dot. NaOCl can be used to start disinfecting the root canal space as you progress, but the main alternating irrigants are 17% EDTA and alcohol until you can navigate the canal space with a file.
A subtle file “stick” will be noted as you start to open up the “white dot” and the root canal space is increased sufficiently to have the file tip enter it. A hard-tipped fine carbon steel straight tip endodontic explorer is useful. Many explorer tips are too wide and two soft and bend upon pressure. Once an explorer “stick” is noted, try a small file to see if it will stick. If not keep progressing with the “penetration and staging” technique of using a small microbur 1 mm, then widening and flattening a smooth “stage” with a larger round carbide bur.
There will be a level of penetration that approximates the depth you noted some minute canal space on the preliminary radiographic images. In the one presented case, it was expected to achieve patency at the depth of the canal stick, but there was no canal patency achieved. A horizontal radiograph was taken with the file in place and it was noted that the file was correctly on line, but just a fraction of a millimeter from the noted root canal space in the apical root Figure 15). This allowed confidence to perform one more small penetration with the small Munce bur and expectedly a small file dropped into the canal.
- Once the canal is found and a file drops in the root canal system can be cleaned and shaped routinely, calcium hydroxide placed, and temporized (Figures 16, 17, and 18).
Key Learning Points:
1. Thoroughly study the root anatomy with sufficient radiographic imaging
2. Place the rubber dam clamp as deeply onto the root as you can
3. Perform the “Penetration and Staging” technique with small penetrations no deeper than 1mm before widening a flat smooth stage
4. Check the patency of the identified white dot with a sharp, narrow, inflexible endodontic explorer
5. Constantly flush with a chelating agent like 17% EDTA to remove debris
6. Be patient.
7. Tertiary dentin is diseased unnaturally formed dentin and not important to preserve.
Final Note: Endodontic treatment cannot be performed expertly without a microscope.