Does Anatomy Matter? Having the Tenacity to Solve Complex Challenges

INTRODUCTION
As dentistry and dental medicine become an increasingly elaborate academic system, actions taken on the clinical frontline are required more often to be based on evidence.¹ Clinical judgments need to be built on a sufficient foundation. However, when speaking about complex root canal systems and human skills, there is a sheer number of variables that can influence successful treatment.^2,3 Therefore, we sometimes have to look beyond our initial impressions and use persistence to solve these challenges.

In line with the remarkable advancements made in recent years, the cone beam CT (CBCT) has successfully allowed the production of easy-to-assess 3-D data.⁴ Unlike conventional digital radiographic images, CBCT scans help us to visualize a 3-D concept of root canals; however, they still may not be enough to cover whole root canal systems. This article will present several case examples in which tenacity was necessary to allow a greater glimpse of the anatomical diversity and also the difficulty of treating such systems.

CASE 1
The diseased tooth was a maxillary central incisor that displayed a significant lesion (Figure 1). After achieving patency by removing the crown and the metal post, root canal shaping was performed.^5-7 The diameter of the root apex was as large as a No. 70 file, due to the partial pathologic absorption of the apex. Active irrigation was applied with a 5% sodium hypochlorite (NaOCl) solution and a 17% ethylenediaminetetraacetic acid (EDTA) solution.⁸ After the root canal was dried, vertical condensation filling was performed using non-standardized gutta-percha.⁹ An entrance to a lateral canal was found at the middle part of the root using a digital radiographic image taken after down-packing. The presence of this lateral canal was uncovered as the gutta-percha had slightly penetrated it (Figure 2). Bacteria lurking in an uncleaned lateral canal may cause a new lesion in the future if untreated.¹⁰ Therefore, the gutta-percha was removed to the point directly under the entrance to the lateral canal, and then this entrance was confirmed via microscope. Next, chloroform was administered to the inside of the root canal, and a precurved No. 10 K-file was inserted into the entrance (Figure 3). Following this, the lateral canal was shaped gradually using a Micro-Opener (Micro-Openers & Debriders [DENTSPLY Maillefer]).

CASE 1 Figure 1. The pretreatment image. Maxillary left central incisor with a significant lesion around its apex. Figure 2. A small lateral canal entrance was observed in the middle of the root canal after the down-packing. Figure 3. Part of the gutta-percha was removed and the lateral canal was explored. Figure 4. The lateral canal was followed to root surface and patency was achieved after much persistence. Figure 5. After a short back-filling, a new lateral canal was discovered. Figure 6. Patency was achieved after tenaciously exploring this new lateral canal. Figure 7. Both lateral canals were completely shaped, cleaned, and filled. Figure 8. The 18-month recall. The lesion had completely healed.

Negotiating the lateral canal proved to be extremely difficult, but patency was eventually achieved by persistently repeating the pecking motion and then cleaning (Figure 4). A digital radiograph was taken after completing a partial back-filling. However, a new entrance to yet another lateral canal was uncovered as a result of the prolonged negotiation and root canal cleaning (Figure 5). The gutta-percha was stripped once again to the point right underneath the entrance of the first lateral canal and negotiation to the second lateral canal was started. Patency was finally achieved thanks to the tenacious attack that continued for many hours (Figure 6). The root canal filling was completed by performing another back-filling. Both lateral canals were shaped, cleaned, and filled (Figure 7). Figure 8 shows an image of the 18-month recall.

CASE 2
The patient complained about the appearance of the sinus tract, which was caused by the pulp necrosis of the left mandibular first molar. A large lesion was observed around the distal buccal (DB) root apex (Figure 9). A root canal was shaped after opening a chamber, then active irrigation was performed with a 5% NaOCl solution and a 17% EDTA solution.^5-8 For this case, the root canal filling was performed using a GuttaCore (Dentsply Sirona).

Although the treatment appeared to progress smoothly, the DB gutta-percha line looked unnatural in the postoperative radiographic image (Figure 10). It suddenly warped near the root apex. It is generally held that an endodontic lesion implies the locations of the portals of exit10 which, in this case, contradicted the fact that the endodontic lesion did not match the path of the root canal. Therefore, a CBCT examination was performed. As a result, it was evident that the line of the root canal filling material did not match the expansion of the lesion (Figure 11). Therefore, the root canal was examined by stripping the gutta-percha up to the point before it curved suddenly. A fairly long time was spent in search of an additional root canal, but none was found. There was no choice other than to once again carefully repeat the active irrigation and then apply the vertical condensation method. However, the digital radiographic image taken after the down-packing revealed a very tiny entrance to another root canal (Figure 12). So the gutta-percha was stripped once again in order to search for the root canal. Patency was finally achieved after a prolonged negotiation (Figure 13). This was due to the root canal being considerably constricted. After completing the root canal shaping, this system was filled (Figure 14).

CASE 2 Figure 9. Pretreatment image. Figure 10. The path of the gutta-percha in distal buccal (DB) root curved suddenly closer to the terminus. Figure 11. The results of a CBCT examination showed the possible existence of an additional root canal in the DB root. Figure 12. Despite extensive searching, the entrance of the root canal was only discovered after methodical root canal irrigation and vertical condensation was performed. Figure 13. Newly discovered opening was negotiated and finally the entire canal was fully explored. Figure 14. This image shows the result of the final filling.

CASE 3
The patient was undergoing preoperative orthodontics for orthognathic surgery. Since a tooth with an insufficiently treated root canal is, at times, liable to become a source of contamination during surgical procedures, the surgeon in charge of this patient requested the retreatment of the root canal of the left maxillary first molar. The diseased tooth (Figure 15) had a long root trunk, and access to each root canal proved to be extremely difficult. Furthermore, a large ledge was found in each root canal due to insufficient treatment performed by the previous clinician in charge. The negotiation, shaping, cleaning, and filling of the root canal was extremely prolonged and included removal of the ledges except for the DB root.⁶

Negotiation of the DB root was continued using ultrasonic chips and files, but patency was not achieved. Therefore, an apicoectomy to the DB root was planned (Figure 16). For this purpose, the root was filled with mineral trioxide aggregate (MTA) (ProRoot MTA [Dentsply Sirona]) beforehand (Figure 17). A CBCT image was taken for the purpose of getting a 3-D image of the root’s anatomy. During this process, it was discovered that the root canal, where the MTA filling had been performed, was actually a completely fake root canal (Figure 18).

CASE 3 Figure 15. Pretreatment image. The tooth had a long root trunk and severe ledges in the root canals. Figure 16. Patency was achieved on all root canals except DB root canal. Therefore, an apicoectomy after the ProRoot MTA (Dentsply Sirona) filling was planned. Figure 17. The DB root canal filled with mineral trioxide aggregate (MTA). That MTA can be observed along the root on the buccolingual aspect. Figure 18. The DB root canal filled with MTA was not the real root canal. It had been identified incorrectly in previous treatments. Figure 19. The real DB root canal after successful shaping, cleaning, and packing.

In the previous treatment, the incorrect DB root had been shaped halfway by the clinician. Making assumptions can easily distort judgment, even when we are past the threshold value of what we consider reasonable. This is because our own experiences can sometimes blind us to other possibilities. Once the previous mistaken treatment was understood, a search was once again performed to find the root canal opening using ultrasonic chips. By doing this, the original root canal was discovered, and finally it was enlarged, shaped, cleaned, and packed (Figure 19).

DISCUSSION
Although the most carefully administered root canal cleaning may not necessarily help reveal all lateral canals, it is important for achieving a successful 3-D root canal filling. These efforts may give us clues as shown in the first case. These clues do not necessarily guarantee penetration and, in a sense, the successful tracing in first case may be a rare example. However, the pathway of the dental pulp undoubtedly continues to the root surface without exception. Efforts to patiently and untiringly continue this pursuit contribute heavily to successful treatment of complex cases.

For the second case, the existence of a second root canal was suspected owing to the fact that the first root canal filling resulted in a sudden curve. If the curve were not so severe, it is likely a CBCT examination would not have been performed. Despite being an initial treatment, the main canal was constrained and penetration proved to be difficult. It was realized that the complexity and probabilistic technical aspect of the root canal anatomy often hinders successful treatment.

Finally, it is important to realize traces of previous treatments are, at times, totally unreliable. One can easily be led by the presupposition that the distance of the root canal expansion from the root canal orifice has a limited threshold value, and once this is passed, one is intuitively led to believe the pathway will continue in same way. Thus, one is liable to form a false belief of where the root canal really is. This is despite the fact that one can easily detect a variation in direction if the expansion stops at a very short distance from the root canal opening. Furthermore, if this deviation is related to the mesiodistal position, a standard digital radiographic examination can be extremely beneficial. However, in the case where a variation in the relationship of the buccolingual position exists, it is almost impossible to find the original root canal using a digital radiographic examination. However, in this case, a coincidental combination of performing a CBCT examination after inserting a MTA contrast medium into the root canal helped detect this error. As a result, the mentality of never giving up and maintaining the pursuit was critical in clearing the way to overcome these obstacles.

CLOSING COMMENTS
Even as technology advances and our tools undergo changes, the anatomical diversity of the root canal¹¹ remains the same. Any lesion of endodontic origin can be completely cured by removing the diseased tooth, which in turn removes the entire root canal systems. Realistically, one must remember, it is nearly impossible to do this while leaving the dentine. However, we can achieve what is possible by dreaming of the impossible. Naturally, scientific data is vital to achieve our goals, but tenacity is also an indispensable ingredient for the successful treatment of complex root canal systems. This is because the endodontic world can often be stranger than fiction.

Acknowledgment
I would like to take this opportunity to express his heartfelt gratitude to Dr. Clifford J. Ruddle, who taught me the importance of tenacity. Furthermore, without his technical and philosophical guidance, none of this would have been possible. His continuous support throughout my career has been both influential and invaluable.

References

1. Brunette DM. Critical Thinking: Understanding and Evaluating Dental Research. Chicago, IL: Quintessence Publishing; 1996.
2. West JD. Perforations, blocks, ledges, and transportations: overcoming barriers to endodontic finishing. Dent Today. 2005;24:68-73.
3. West JD. Rules of engagement: mastering the endodontic game, Part 1. Dent Today. 2006;25:94-101.
4. Ee J, Fayad MI, Johnson BR. Comparison of endodontic diagnosis and treatment planning decisions using cone-beam volumetric tomography versus periapical radiography. J Endod. 2014;40:910-916.
5. Ruddle CJ. Cleaning and shaping root canal systems. In: Cohen S, Burns RC, eds. Pathways of the Pulp. 8th ed. St. Louis, MO: Mosby; 2002.
6. Ruddle CJ. Nonsurgical endodontic retreatment. In: Cohen S, Burns RC, eds. Pathways of the Pulp. 8th ed. St. Louis, MO: Mosby; 2002.
7. Schilder H. Cleaning and shaping the root canal. Dent Clin North Am. 1974;18:269-296.
8. Ruddle CJ. Endodontic disinfection: tsunami irrigation. Endod Prac. 2008;11:7-16.
9. Schilder H. Filling root canals in three dimensions. Dent Clin North Am. November 1967:723-744.
10. Ruddle CJ. Radiographic lesions of endodontic origin: significance of location. Endod Rep. Spring/Summer 1987:10-13.
11. Hess W, Zürcher E, The Anatomy of the Root Canals of the Teeth of the Permanent Dentition. New York, NY: William Wood; 1925.

Dr. Okumura graduated from Osaka Dental University in 1995 and completed his postgraduate study at the Institute for Frontier Medical Sciences, Kyoto University. He received a PhD from Kyoto University in 1999. He currently maintains a private practice in Kobe, Japan, and he can be reached at okumura@s-pic.jp or via the website s-pic.jp.

Disclosure: Dr. Okumura reports no disclosures.

Related Articles

Rules of Engagement: Mastering the Endodontic Game, Part 2

A Short Case Study: Relax, Don’t Extract!

CBCT Imaging’s Insight Into Endodontic Retreatment Success