Three patients with varying chief complaints were referred to the postgraduate endodontic clinic at Ajman University, United Arab Emirates, for treatment. Their medical histories were reviewed and considered non-contributory in all cases. Intraoral examination revealed either large crown fillings or visible caries lesions. All necessary clinical and radiographic assessments were conducted, including periodontal probing, cold tests, and periapical radiographs, followed by preoperative cone beam computed tomography (CBCT) after identifying an additional root on radiography. Following the pulpal and apical diagnoses, all three cases were classified as highly difficult according to the case difficulty assessment of the American Association of Endodontists, and root canal treatment was recommended. Informed consent was obtained from all patients. Infiltration anesthesia (1.8 mL of 2% lidocaine with 1:80,000 epinephrine) was administered. Under rubber dam isolation, access cavities were prepared using round and Endo-Z endodontic burs. The pulp floor morphology was inspected under 25× magnification using a Leica M320 dental operating microscope (Leica Microsystems, Wetzlar, Germany). Orifices of the canals were refined with ultrasonic tips (ET 20D- Suprasson® P5 Newtron SATELEC; ACTEON, Merignac, France). Root canals were negotiated, and patency was achieved using stainless-steel ISO size 8–10K hand files (Dentsply Sirona, Ballaigues, Switzerland). Working length was determined with an electronic apex locator (Root ZX, Morita, Japan) and confirmed with periapical radiographs. Chemo-mechanical preparation of all canals was performed with different rotary systems, complemented by copious irrigation with 2% sodium hypochlorite (NaOCl) delivered using a side-vented 27G needle (Monojet, Covidien, Mansfield, USA). The final irrigation protocol consisted of NaOCl, followed by 17% ethylenediaminetetraacetic acid and then NaOCl, which was activated using Acteon® Irri Safe™ Passive Ultrasonic Irrigation files. The canals were dried with paper points and obturated with calibrated gutta-percha and resin-based sealer (AH Plus, Dentsply Sirona, Konstanz, Germany) using the continuous wave of condensation technique. Finally, pulp chambers were cleaned with alcohol, canal orifices sealed with flowable resin (3M Filtek Supreme Flowable Restorative, USA), and access cavities restored with composite restorations.

A 28-year-old Sudanese man was referred by a general dentist for root canal treatment of the left maxillary first premolar (#24). The referring practitioner had initiated endodontic therapy but was unable to locate all canals due to the complexity of the root canal system. On examination, the tooth had no response to the cold test and no tenderness to percussion. The preoperative periapical radiograph did not clearly delineate the external root morphology (Figure 1a), so a CBCT scan of the tooth was requested. The scan revealed complex root canal anatomy with a long buccal canal bifurcation and three separate roots, with no visible periapical radiolucency. A diagnosis of previously initiated endodontic therapy with normal periapical tissue was established. The access cavity was refined utilizing an Endo-Z bur and ultrasonic tips to enlarge the buccal canal orifice and selectively remove dentin up to a depth of about 12.8 mm. This modification facilitated the exposure of the bifurcated canals and the removal of dentinal overhangs, thereby establishing straight-line access to both canals. Working lengths of the canals were determined and verified radiographically at 26 mm for the mesiobuccal (MB), distobuccal (DB), and palatal (P) canals. The Hyflex-CM rotary system (Hyflex CM, Coltene/Whaledent, Altstätten, Switzerland) was used for mechanical instrumentation. After all canals were shaped and disinfected, they were obturated as described previously (Figures 1a–h).

A 22-year-old Sudanese man was referred for root canal treatment of the left maxillary second premolar (#25). The patient's primary complaint was severe, lingering pain on exposure to cold water. Cold sensitivity testing confirmed prolonged pain lasting over 30 s. The preoperative periapical radiograph revealed radiolucent areas on both the mesial and distal aspects of the tooth, suggestive of carious lesions. There was evidence of widening of the periodontal ligament space with no periapical changes (Figure 2a). Similarly, the preoperative periapical radiograph of tooth #25 could not clearly delineate the root morphology. Therefore, a CBCT scan was requested for a more detailed evaluation. Upon reviewing the CBCT, a canal bifurcation was observed in the coronal portion of the root at approximately 11.2 mm from the coronal reference point, resulting in two distinct canals, MB and DB, each with a separate canal path that then fused together along the length of the root at 17 mm and ended in one exit. Based on clinical and radiographic findings, a diagnosis of symptomatic irreversible pulpitis with normal periapical tissues was confirmed, and root canal treatment was initiated. Following the removal of the caries and the underlying weakened dentin, the access cavity was modified to facilitate a straight-line path into the canals. The working length of the canals was confirmed at 22 mm for the MB and DB canals and 23 mm for the palatal canal. The ProTaper Ultimate system (Dentsply Sirona, Ballaigues, Switzerland) was used for shaping the root canals. All other procedures were completed as described earlier (Figure 2).

A 42-year-old Sudanese woman presented to the postgraduate endodontic clinic with the chief complaint of pain and tenderness in the region of tooth #24. Clinical and radiographic evaluation confirmed a first premolar that had undergone previous root canal treatment and was restored with a crown. The tooth was tender to apical percussion, raising suspicion of a missed canal (Figure 3a). Therefore, a CBCT scan was performed for detailed evaluation. From the scan, a buccal canal bifurcation was observed in the apical portion of the root, resulting in two distinct canals—the MB and the missed DB—each with independent trajectories along the length of the root and associated with a large periapical lesion (Figures 3a–f). A diagnosis of a previously treated tooth with symptomatic apical periodontitis was established, with the missed canal identified as the most likely cause of the failure. After administering anesthesia, crown removal was initiated by sectioning the porcelain with a straight diamond bur, followed by cutting the metal part with a transmetal bur. Crown removal was completed with plastic instrument luxation. Removal of the previous obturation material was performed using Endo Star retreatment files (Poldent, UK). The working lengths were established at 17 mm for the palatal canal, 16 mm for the MB canal, and 15 mm for the newly identified DB canal. Canal preparation was performed using the WaveOne Gold Primary (WOG, Dentsply Maillefer, Ballaigues, Switzerland) file system. All canals were chemo-mechanically prepared and obturated as described earlier.