Root canal treatment of an invaginated maxillary lateral incisor with a C-shaped canal
Carlos Bóveda, Od* / Mariela Fajardo, Od MS** / Beatriz Millán, Od***
* Attending Professor, Endodontics Department, Universidad Central de Venezuela, Caracas, Venezuela. Private Practice, Caracas, Venezuela
** Chief Graduate Endodontics, Universidad Central de Venezuela. Private Practice, Caracas, Venezuela
*** Private Practice, Caracas, Venezuela
The endodontic treatment of an atypical maxillary lateral incisor that contained a c-shaped root canal is presented. The unusual anatomic configuration of this particular tooth and the advantage of using image magnification to facilitate endodontic treatment are discussed. (Quintessence Int 1999;30:707-711)
The fact that the maxillary lateral incisors generally present a single root and a single canal led in the past to the belief that this is the only anatomical possibility. 1,2 However, case reports 3- 11 have shown that these teeth may present different anatomic configurations, including the dens invaginatus , also known as the dens in dente. The anomalous development in these teeth varies from a simple coronal groove to a sac that extends beyond the cementoenamel junction all the way down to the apex, forming a second foramen.12 The prevalence of this anomaly may be higher than generally believed; reported frequencies vary up to 10%.13
Cases of dens in dente are known to be treated surgically,14 although non surgical root canal treatments have also reported to be successful.11,15 These procedures were performed in teeth with single or multiple canals. However, the internal shape of these canals has never been described, even though radiographic analysis and results suggest strong differences between these canals and the common conical configurations. The present case report describes the endodontic treatment of an invaginated maxillary left lateral incisor with 3 canals, 1 of which was a C-shaped canal.
An 11-year-old girl was referred for endodontic treatment. Swelling had developed around the maxillary left lateral incisor 2 weeks prior to the initial evaluation. Antibiotics (Amoxicillin, 500 mg/8 h) had been prescribed for seven days.
The patient had a non-contributory medical history. At the time of the first visit, the patient was asymptomatic. Clinical examination revealed the maxillary left lateral incisor to have an unusually shaped, extremely round crown with a small cusp emerging from the incisal border. A thin, vertical groove extended through the cingullum and advanced apically. The tooth was non-carious and slightly discolored. There was no history of trauma, and the tooth showed no mobility. Discomfort was present on percussion as well as pain on palpation of the periapical area. Results of the thermal test and electrical pulp test were negative.
The radiographic examination revealed an invaginated tooth with a periapical radiolucency, measuring 4x6 mm, lateral to the apical foramen (Fig. 1) [The malformation has been classified as a unilateral dens invaginatus type III by Oehlers. 12].A diagnosis of necrotic pulp and periapical abscess was made.
The endodontic treatment was performed with an OPMI 1FC Surgical Microscope (CZeiss, Inc), to enhance the visual capacity of the operator. The tooth was isolated and initial access was gained. At this time, a large canal was found in the lingual aspect of the tooth (Fig. 2). No vital pulp tissue was found; therefore, the necrotic contents of this canal were removed to the working length (Fig. 3). The canal was then sealed temporarily with a dry cotton pellet and Cavit (ESPE).
Although the patient was scheduled to return 1 week later, she came back after 6 weeks and reported absence of symptoms during this period. At this point, the access was extended in an attempt to locate other canals evident in the radiographs. An ST 07 insert was used in the Enac Ultrasonic Endodontic System (Osada Electric) to remove the dentin from the pulpal chamber in a bucal direction, exposing a sulcus containing vital pulp (Fig. 4). This ribbonlike canal started at the mesial aspect of the tooth, then swept around the bucal, defining a 160-degree arc, to end at the bucal-distal angle. At this angle, a new single canal, also containing vital pulp, was found.
The C-shaped bucal canal was 3.5 mm wide for its entire mesiodistal extent. This could be ascertained by placing a # 10 file along the entire mesiodistal dimension. Also, 2 #15 files were inserted at each extreme of the canal and they maintained their parallelism all along the root. Figure 5 shows these files along with 1 #35 file in the lingual canal and 1 #20 file in the distal canal.
The working length was determined with the aid of an electronic apex locator (Root ZX, J. Morita). To continue the preparation of the narrow, C-shaped canal, a 19% ethylenediamine tetraacetic acid lubricant-chelating gel was used (File-Eze, Ultradent). At this time, the tooth showed a large conical and straight lingual canal, some hard tissue in the center of the pulp chamber, a wide C-shaped buccal canal, and a small, conical distal canal, noticeably curved (Fig. 6 and 7). All the internal spaces found were cleaned and shaped to the working length, and the tooth was sealed temporarily with a dry cotton pellet and Cavit.
Preceding the next visit (1 week later) the patient was once again asymptomatic. The canals were obturated with laterally condensed gutta-percha (Hygenic) and sealer (Pulp Canal Sealer, Kerr) (Fig. 8). The canals were filled from minor to major wideness in the following order: the distal canal, the lingual canal and then the C-shaped buccal canal. To allow visualization of the anatomy and monitoring the procedure, a radiograph was taken each time a canal was filled (Figs. 9 and 10). The coronal access was sealed with glass ionomer cement (Ketac Cem, ESPE). The final radiograph of the root canal treatment shows the results obtained (Fig. 11).
After 10 months, the tooth remained asymptomatic. The recall radiograph taken at this time revealed complete periapical healing and no remaining radiolucency (Fig 12).
The dens in dente may present different anatomic configurations. As Kronfeld stated, 16 the dens invaginatus may form because of retardation in the growth of a portion of the enamel that occurs while surrounding dental tissues continue to grow normally. Communicating channels are created between the invaginated cavity and the pulp chamber. This facilitates bacteria penetration once the tooth erupts in the oral cavity, causing the pulp tissue to undergo inflammation, degenerative changes and eventual pulp necrosis.
Because of the complex and partially unknown anatomic configuration of these teeth, nonsurgical root canal treatments become problematic; it is difficult to ensure complete removal of diseased pulp or necrotic tissues from the root canal system. In this particular case, the use of the operating microscope proved to be of great advantage because it improved visualization and recognition of colors and textures, enhancing the operator's ability to observe in detail the hard and soft structures of the tooth. This lead to an extensive canal identification and therefore to a more precise preparation.
The treated invaginated maxillary lateral incisor was unusually round, probably related to the C-shaped canal that was found, a configuration previously described only in posterior teeth.17-20 Whether this type of configuration is occasionally found in invaginated teeth, and is neither recognized nor treated because of visual limitations, remains a question.
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