A Central Incisor With 4 Independent Root Canals.docx

A Central Incisor with 4 Independent Root Canals: A Case Report Abstract The maxillary central incisor is the tooth with the least anatomic variations. Despite the fact that several studies have reported a prevalence of 100% for the presence of a single canal, root canal aberrations of maxillary central incisors with up to 3 canals have also been reported. Such cases represent both a diagnostic and technical challenge to the clinician. The present case describes root canal treatment performed in a maxillary central incisor with 4 canals. The detection of all canals was achieved by examination of the pulp chamber floor with the help of the dental operating microscope as well as careful examination of intraoral radiographs. The canals were prepared with hand and rotary instruments and obturated with a warm guttapercha technique. The present report is the first to describe a maxillary central incisor with 4 canals in a tooth with no developmental abnormalities. It stresses the importance of using a dental operating microscope during endodontic treatment as well as questioning the routine use of cone-beam computed tomographic imaging for similar cases. (J Endod 2015;-:1–4) Complete debridement of the root canal system is 1 of the most important factors affecting the success of root canal treatment(1). It is essential to have a good knowledge of the root canal anatomy of the specific tooth to be treated and to be aware of possible variations and treatment options (2). Different studies have investigated the root canal anatomy among different types of teeth and reached the conclusion that the maxillary central incisor is the tooth with the least anatomic variations, showing a single root canal in 100% of the cases (3–5). Case reports describing 2- and 3-canal central maxillary incisors have been previously published (6, 7). Mangani and Ruddle (8) reported the case of a 4-canal maxillary central incisor. This case described dens invaginatus type II (Oehlers). Developmental abnormalities, such as invagination, fusion, or germination, have been relatively frequently described in anterior teeth (9). When this occurs, the canal anatomy might be altered, and various combinations of canal number and configuration may consequently be encountered. Cone-beam computed tomographic (CBCT) imaging was recently suggested as a diagnostic aid in the identification of potential accessory canals in teeth with suspected complex morphology (10); however, it remains unclear whether the use of CBCT imaging would improve the outcome of root canal treatment. Furthermore, the additional radiation and costs are not always justified (11). The present report describes a root canal treatment conducted in an upper maxillary central incisor presenting 4 canals and no developmental abnormalities. The identification, preparation, and obturation of the canals are described in details. Case Report A 13-year-old female patient with a noncontributory medical history (American Society of Anesthesiologists I) was seen by her general dentist concerning spontaneous pain and swelling in

the anterior region of her upper jaw. The general practitioner diagnosed pulp necrosis of the upper left central incisor (tooth #8) associated with an acute apical abscess and initiated root canal therapy. He accessed the pulp chamber, instrumented a single canal in conjunction with 2% sodium hypochlorite (NaOCl) irrigation, and sealed the access cavity temporarily. Despite a reduction in pain and swelling during the following days, the tooth remained sensitive to percussion and palpation. Therefore, the patient was referred to an endodontic clinic for further evaluation and treatment. During the initial radiographic and clinical inspection, no developmental abnormalities of the anterior teeth could be identified (Fig. 1). The previous temporary filling was intact, and a fluctuant localized swelling could be observed buccally at the level of the root apex of tooth #8. The tooth was sensitive to percussion and palpation, and class I mobility without any deep pocket was recorded. A single canal and extensive periapical radiolucency were visible radiographically as well as a sudden change in the canal width at the midroot level (Fig. 2A–G). Previously initiated root canal treatment associated with an acute apical abscess was diagnosed, and root canal treatment was resumed. After administering local anesthesia, the tooth was isolated with a rubber dam, and the temporary restoration was removed. Four root canal orifices were located at the midroot level with the help of a dental operative microscope (DOM) (Zeiss Pico; Zeiss, Gottingen, Germany) at 10 magnification. One large canal was positioned lingually, and 3 narrower canals were located buccally (Fig. 3). The working lengths were determined by an apex locator (Root ZX II; J Morita, Irvine, CA) and confirmed radiographically. (Fig. 2). A glide path up to a size 20 was achieved in all 4 canals with stainless steel hand files (K-Flexofile; Dentsply, Ballaigues, Switzerland), and the preparation was completed using Profile rotary files (Dentsply) up to a size 30, 0.04 taper. The canals were irrigated with 1 mL 2% NaOCl at each change of file. Ultrasonic activation was performed by a stainless steel size 25, .00 taper file (IrriSafe; Acteon, Merignac, France) placed 2 mm short of the working length and driven by an ultrasonic device (P5 Booster; Satelec Acteon, Merignac, France) for 20 seconds at power setting 5. Activation was repeated 3 times with delivery of 1 mL 2% NaOCl between each activation phase. Thereafter, 17% EDTA was delivered and left in the canals for 1 minute. All irrigants were delivered with a 30-G open-ended needle (Navitip; Ultradent, South Jordan, UT) placed slightly short of the binding point. The canals were then dried with sterile paper points and immediately filled with gutta-percha (Autofit; Analytic, Glendora, CA) and AH Plus sealer (Dentsply) by using the continuous wave of condensation technique with the tip of the heat carrier reaching 4 mm from the working length and a backfill with a warm gutta-percha gun (Obtura II; Obtura Spartan, Fenton, MO) for the middle and coronal thirds. The access cavity was then restored during the same visit with composite (Venus; Heraeus Kulzer GmbH, Hanau, Germany) placed with an incremental technique, and dental occlusion was checked. The patient returned for follow-up at 6, 12, and 24 months and was completely symptom free. The clinical examination revealed that the tooth was neither percussion nor palpation sensitive. The mobility and probing depths were within normal range. Radiographic control a continuous periodontal ligament space with no signs of apical periodontitis (Fig. 2).

Discussion The prevention and treatment of apical periodontitis are the main objectives of endodontic therapy (12). Adequate instrumentation, disinfection, and obturation of the root canal system together with the placement of a sealing coronal restoration are the main steps toward achieving this goal(13)and require a good understanding of root canal anatomy. Mangani and Ruddle (8) already reported a case of dens invaginatus presenting 4 canals in an upper central incisor. This invagination can occur at the crown of the tooth and sometimes might extend within the root, creating complex canal systems(9). To our knowledge, no reports of a 4-canal maxillary central incisor presenting no developmental abnormalities have been previously published. The patient was referred to our clinic because of the persistence of symptoms after the initial therapy. During the first treatment, only a single canal was located and cleaned. Incomplete debridement of all the canals was the most likely cause for the perpetuation of the symptoms despite the therapy. Once all the canals were located and could be negotiated and cleaned, the symptoms disappeared, and a follow-up xray showed the healing of the periapical alveolar bone. This highlights the importance of a good understanding of the canal anatomic complexities to be able to effectively disinfect the root canal system. In the preoperative radiograph, an abrupt narrowing of the canal at the midlevel of the root indicated the possibility of a split of the main canal (14). This split was confirmed with the help of the DOM. The DOM is an important tool in the armamentarium of modern endodontic therapy. It has been shown that its use could help in locating additional canals during endodontic treatment (15, 16), improving treatment accuracy, and expediting treatment (17). Potential drawbacks of the use of the DOM are the required learning curve and high investment costs. The use of the DOM has been shown to improve the ability of the practitioner to locate canals (18) although it remains unclear whether its use would improve the outcome of endodontic therapy (19). CBCT imaging is a modern diagnostic tool that can provide additional 3-dimensional information to the practitioner for diagnostic purposes(20). For the present treatment, no CBCT imaging was performed because no developmental abnormality could be detected by clinical and radiographic inspection. A recent position statement published by the European Society for Endodontology recommends the use of CBCT imaging for the diagnosis and treatment of teeth in which development abnormalities are present (21). A recent joint position statement of the American Association of Endodontists and the American Academy of Oral and Maxillofacial Radiology on the use of CBCT imaging states that limited field of view CBCT scanning should be considered the imaging modality of choice for the initial treatment of teeth with the potential for extra canals and suspected complex morphology (22). It is unclear whether CBCT imaging is superior to digital periapical radiographs for the detection of additional canals (15, 23). The ALARA (as low as reasonably achievable) principle

states that every effort should be made to keep the patient’s exposure to ionizing radiation as low as practically possible (24). In the present case, 4 independent canals could be located and successfully treated with the help of the DOM but without a CBCT scan. The visualization of the pulp chamber floor patterns with the DOM allows the clinician to trace the root canals in order to eventually access them. However, it does not allow visualization of deep dilacerations or apical bifurcations. Although CBCT imaging could show the root canal system 3-dimensionally (21), it will not necessarily allow access to deep anatomic aberrations without the risk of damaging the root. Future studies should further investigate and compare the ability of CBCT imaging and the DOM in locating root canals against a gold standard, such as histologic sectioning, as well as the ability of both technologies to improve the clinical outcome. Conclusion The present report is the first to describe a maxillary central incisor with 4 canals in a tooth with no developmental abnormalities. It stresses the importance of using the DOM during endodontic treatment as well as the necessity of being attentive for morphologic variations that have not been previously reported in the literature. Successful treatment was performed without the use of a CBCT scan, questioning the routine use of CBCT imaging for similar cases.