Trouble Curve: Endodontic Management of Severely Curved Root Canal System - A Case Report

INTRODUCTION

Successful endodontic treatment includes thorough shaping and cleaning of the root canal system, most of the root canals have multiple curvatures along their path, which pose difficulty in canal instrumentation¹ .

Occurrence of teeth with straight root or root canal is a rare rather than normal because most of the teeth show some curves or bends in the canal. In addition, root canals may have many planes of curvature throughout their length² . Canal curvature can be a dilacerated canal, S-shaped canal, gradual curvature of the root, and sharp curve in the apical third of root³ . John Tomes, in 1848, named such curvatures as “dilacerations.” It refers to an angulation or a sharp bend or a curve in the root or crown of tooth or a deviation or bend in the linear relationship of a crown of a tooth to its root.^4,5 (figure 1)

The widely accepted cause of dilacerations is an acute mechanical injury to the primary predecessor tooth which leads to the dilaceration of the underlying developing permanent tooth. The calcified part of the permanent tooth germ is shifted in such way that the rest, non-calcified part of the permanent tooth germ forms an angle⁶ .

Some syndromes associated with tooth dilaceration are Smith Magenis syndrome, Ehlers-Danlos syndrome, Axenfeld-Rieger syndrome, and congenital ichthyosis⁷ .

Dilacerations are often seen in both permanent and deciduous dentitions, but the incidence in primary tooth is extremely low⁷ . It is present equally in maxilla and mandible. Mandibular second molar is the mostly affected tooth (1.6%) followed by maxillary first molar (1.3%) and mandibular first molar (0.6%). It is rarely detected in the maxillary canine, second premolar and mandibular lateral incisor, canine and first premolar⁸ .

Clinically, procedural errors like formation of ledge, canal blockage, root perforations and zipping are the undesirable accidents that can occur after preparation of curved canals. Management of curved canals is an endodontic challenge⁹ .

This case report illustrates a rare occurrence of dilacerated mandibular right second premolar and its successful endodontic management.

CASE REPORT

A 35-year-old female patient reported to Department of conservative dentistry and endodontics with diffuse pain in the mandibular right quadrant. The patient gave a history of pain for last 2 months that aggravates while sleeping and relieves after taking the analgesics. No relevant medical history was observed. The intraoral examination revealed a faulty restoration in relation to # 45 associated with tenderness on percussion. The IOPA revealed a radiolucency below the restoration extending into the pulpal region with no signs of periapical pathosis (figure 2)Vitality testing (cold and electronic testing) elicited sharp lingering pain after the removal of the stimulus. The pulpal diagnosis was consistent with symptomatic irreversible pulpitis, and the periapical diagnosis was consistent with no radiographic periapical disease. Apart from these findings, the tooth showed dilacerated root. There is history of endodontic treatment of 46 eleven years back.

Once the treatment plan was established, the patient signed an informed consent. The tooth was anesthetized, and access opening was done under rubber dam isolation. After gaining an adequate access, initial inspection of the root canal was done with K-file no.8 & 10, and the patency of root canal was established. Gates Glidden (GG) drills were used sequentially in a stepback fashion (i.e., nos. 1, 2, and 3) to allow easy placement of instruments and to gain a straight line access to the apex. The working length was estimated using an electronic apexlocator (Propex; Dentsply Maillefer) and confirmed with periapical radiograph (Figure 3). The initially pathfinder stainless steel file (SybronEndo, Orange, CA, USA) of intermediate sizes, i.e., no. 13, no. 16, and no. 19, were used and filing sequence was done with 17% EDTA followed by irrigation with saline and 3% sodium hypochlorite (NaOCl). The canals were further enlarged using #15, #20, #25 K files (Mani, Inc, Japan). For confirming the working length and patency of the root canals, no. 8 and 10 stainless steel K-files (Mani, Inc., Japan) were used. Final radicular preparation was carried out using Neoendo Flex files (Neoendo, Orikam) up to 4% taper 25 size of the instrument. After biomechanical preparation, the canals were irrigated, flushed with EDTA 17%, and dried prior to obturation (figure 4). Single cone obturation was done with 25 size 4% taper gutta-percha along with zinc oxide eugenol sealer (Figure 5). The post obturation restoration was done using amalgam.

DISCUSSION

The morphology of root canal system is usually quite complex and highly variable. In the presenceof curvatures, it is very difficult to achieve a proper and complete cleaning and shaping of root canals¹⁰.

The term dilaceration was first used by Tomes in 1848, refers to an angulation or a curve or a sharp bend in the root or crown of tooth or a deviation or bend in the linear relationship of a crown of a tooth to its root ⁵ . According to the American Association of Endodontists and glossary of endodontic terms, dilaceration is defined as a deformity or anomaly characterized by displacement of the root of a tooth from its normal alignment with the crown which may be a consequence of injury during tooth development¹¹.

There are many reasons for dilaceration of tooth. Traumatic injury to the deciduous tooth is considered as the most common cause of dilacerations and other contributing factors include ectopic development of the tooth germ, presence of infection, scar or tumor, developmental anomaly and hereditary factors. If a tooth is doubly affected it is called as bayonet dilaceration¹².

The principle for recognizing root dilacerations vary in the literature. A tooth may have a dilaceration towards mesial or distal direction , or there is a 90-degree angle or greater along the axis of the tooth or root, some authors defined dilaceration as a deviation from the normal axis of the tooth of 20 degrees or more in the apical part of the root⁷ . Determining the direction of curvature will help in maintaining a continuous tapered shapes and prevents structural damage of the endodontic instruments.

Schneider suggested a method to calculate the degree of root curvature based on the angle that is obtained by two straight lines drawn along the flared root canals. And it is categorized as: Straight: 5° or less, Moderate: 10-20° and Severe: 25-70°¹³.

According to Gunday etal, Schneider’s technique emphasized more on canal curvature in coronal aspect, whereas long axis technique which is described by Hankins etal considered the apical curvature and does not consider overall root curvature⁷ .

The main cause of failure of endodontic treatment in curved canals is procedural errors such as ledges, instrument separation, canal blockage, zipping and elbow creation. A knowledge of internal root anatomy is essential for successful endodontic therapy. In the present case, proper attention was directed in radiographic assessment which helped in negotiating root curvature and canal configuration.

According to Gutmann coronal preflaring helps in providing a glide path before rotary NiTi files are introduced for biomechanical preparation and also tactile control of the entire curved canal¹⁴. Also pre flaring holds a greater volume of irrigant that enhance cleaning¹⁴. This step was followed in this case. Pathfinder files are unique alternative to no. 6 and no.8 K files. These files have reduced taper which helps in negotiating the constricted and difficult canals easily with additional benefit of rigidity and enhanced flexibility during canal negotiation. Table 1 depicts the relationship between degree of curvature and incidence of ledge formation.

Precurving of all the hand instruments especially (Ni-TI K files) and use of smaller files (No. 6 or 8) facilitates easy negotiation of curved canal and reduce the amount of transportation to danger areas¹⁵. The balanced force technique is less likely to cause iatrogenic damage, decreases the extrusion of debris apically and maintains the instruments centrality within the root canal^16,17. Ni-Ti alloys are comparatively softer than stainless steel, have a lower modulus of elasticity and are more resilient and show Shape memory and Super elasticity (SE)¹⁸. The rotary files helps in flaring of coronal third and has advantages such as reduced coronal binding of the instruments, less apical extrusion of debris, and effective irrigation of apical third of the canal¹⁹.

CONCLUSION

The endodontic management of severely curved root canals is actually same as that of straight canals. Understanding the complex and varied root canal morphology and its anatomy and choosing a suitable canal preparation technique and instruments more suited for such morphology, will contribute to successful root canal treatment.

ACKNOWLEDGEMENT

I express my sincere and deepest gratitude to Dr. B S Keshava Prasad for the guidance, support, constant encouragement and healthy criticism in preparing this manuscript

CONFLICT OF INTEREST

The authors have stated explicitly that there are no conflicts of interest in connection with this article.