Recognition of anatomical variations is a real challenge for clinicians undertaking therapy regardless of the teeth that are to be treated. The extent of the curvature is one of the most important variables that could lead to instrument fracture. In clinical conditions, two curves can be present in the same root canal trajectory. This type of geometry is denoted as the “S” shape, and it is a challenging condition. This report describes a different clinical and educational scenario where four specialists around the world present different approaches for the treatment of root canals with double curvatures or S-shaped canals. Endodontic therapy is a very nuanced and challenging science and art. The clinical and teaching experience of the authors show different approaches that can be successfully employed to treat challenging teeth having roots with multiple curves. The necessity of precise knowledge of the root canal morphology and its variation is also underlined.
Straight simple root canal systems are exceptions and not rules in the human dentition. Nature frequently demonstrates curved root canal systems of high complexity with multiple curves in different planes [
The aim of this paper is to show four cases of S-shaped canals performed with different approaches by four specialists from different clinical scenarios.
A 40-year-old male patient was referred to the clinic of one of the authors (Jorge Vera) with severe pain to cold stimuli in his upper left maxillary arch. The medical history was noncontributory. All teeth in the area responded within normal limits to thermal cold tests except for the second left maxillary bicuspid. Probing depths were within 3 mm for all teeth of the region. Preoperative radiograph revealed a distal decay in the second left maxillary bicuspid and a double curve or s-shaped anatomy. After considering all findings, a diagnosis of irreversible pulpitis was made (Figure
(a) Initial radiograph, (b) working length radiograph, and (c) final radiograph.
After administrating infiltration anesthesia (articaine 1 : 100.000 epinephrine), the rubber dam was placed and the access cavity preparation was performed with size 2 round burs (KG Sorensen Zenith Dental Aps, Agerskov-Denamark). Sizes .10 K and .08 K files (Dentsply Maillefer, Ballaigues, Switzerland) were initially used with the Slick Gel Lubricant (SybronEndo, Orange County, CA) to try to reach working length. The files initially reached a very short length, so a step-back procedure using 360° counterclockwise movement of each file was performed using K files sizes .15, .20, .25, and .30 (Dentsply Maillefer, Ballaigues, Switzerland) with slight apical pressure. At the completion of the use of the large-sized files, 5.25% NaOCl was irrigated into the root canal preparation and a size .10 K file was taken to working length as confirmed by the Elements Diagnostic Apex Locator (SybronEndo, Orange County, CA) and a check radiograph (Figure
A 60-year-old female patient was referred to the clinic of one of the authors (Antonis Chaniottis) for the evaluation and possible treatment of her left maxillary second premolar. The tooth was sensitive to palpation and percussion. The thermal and electrical pulp testing were negative. Thorough examination of the preoperative radiograph revealed a periapical lesion associated with the apex of the referred tooth and a double curve or S-shaped anatomy (Figure
(a) Initial radiograph showing periapical radiolucency, (b) radiographic confirmation of the working length, and (c) immediate posttreatment radiograph.
After administrating infiltration anesthesia (articaine 1 : 100.000 epinephrine), the rubber dam was placed. Access was achieved by using the size 2 Endo Access bur (Dentsply Maillefer, Ballaigues, Switzerland). Refinement of the access cavity was achieved using the Endo Z bur (Dentsply Maillefer, Ballaigues, Switzerland). Coronal flaring of the canals was performed by using the Protaper SX rotary file (Dentsply Maillefer, Ballaigues, Switzerland).
The length determination radiograph revealed S-curve apical anatomy (Figure
After hand-filing, the sizes 1 and 2 Pathfinder rotary files (Dentsply Maillefer, Ballaigues, Switzerland) were used to working length, followed by scouting with sizes 10/.04 and 10/.06 Race files (FKG Dentaire, La Chaux-de-Fonds, Switzerland) to working length. No further enlargement of the S-curved canals was performed. 6% NaOCl was used to irrigate between each file used. Canal blocking was prevented by using multiple recapitulations with a precurved .08 stainless steel K files (Dentsply Maillefer, Ballaigues, Switzerland) between each rotary file use.
The irrigation efficacy was enhanced after completion of the shaping procedures by passive ultrasonic activation of the irrigant with a size .15 ultrasonic K file (Satelec Acteon Group, Merignac Cedex, France). The canals were next flooded with 17% EDTA solution for 2 minutes followed by a final rinse of sterile water. The canals were dried with size .20 sterile paper points and obturation was performed with the Continuous Wave of Condensation Technique [
Two fine feathered tip gutta percha points (SybronEndo, Orange, CA, EUA) were gauged to .20 and fitted with AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) to working length. An extra fine tip mounted on the Elements Obturation unit (SybronEndo, Orange County, CA) was used at a setting of 200°C 5 mm short of the working length. The apical gutta percha was compacted by using a size 35 Dovgan plugger (G. Hartzell & Son, Concord, CA). Backfilling was performed using high-speed injection of thermoplasticized gutta percha by the Extruder Elements Unit (SybronEndo, Orange County, CA) through a .25 gauge needle (Figure
A 32-year-old female patient was referred the clinic of the one of the authors (Ricardo Machado) with severe pain to cold stimuli in her upper left maxillary arch. The medical history was noncontributory. All teeth in the area responded within normal limits to the thermal and electrical pulp testing unless the left maxillary first premolar that showed a considerable hypersensitivity. Probing depths were within 3 mm for all teeth of the region. Preoperative radiograph revealed the presence of decay all around the crown and a double curve or s-shaped anatomy (Figure
After administrating infiltration anesthesia (articaine 1 : 100.000 epinephrine), the rubber dam was placed. Initial access was achieved by using a 1016HL bur (Dentsply Maillefer, Ballaigues, Switzerland) and refinement of the access cavity was achieved using the Endo Z bur (Dentsply Maillefer, Ballaigues, Switzerland). Coronal flaring of the canals was achieved by using the Protaper SX, S1, and S2 rotary files (Dentsply Maillefer, Ballaigues, Switzerland).
Initial negotiation and scouting of the S-curved canals were achieved with a size .10 stainless steel K file (Dentsply Maillefer, Ballaigues, Switzerland). Working length was verified by using the Elements Diagnostic Apex Locator (SybronEndo, Orange, CA, EUA). Hand-filing was achieved by slowly inserting the K files to the working length followed by passive gentle, withdrawal strokes. This allowed an unobstructed glide path to be developed along the S-shaped curvature with minimal transportation.
After hand-filing, a Crown-Down instrumentation technique [
Two gutta percha master cones (Profile .04—Dentsply Maillefer, Ballaigues, Switzerland) were fit to the radiographic terminus with firm tug back. The cones were coated with AH Plus sealer (Dentsply DeTrey, Konstanz, Germany) and fit to working length with the aid of a size 30 finger spreader (Dentsply Maillefer, Ballaigues, Switzerland). Subsequently, three accessory cones were added. Next a size 40/.02 McSpadden condenser was used limited to placement in the coronal two-thirds of the root. The tooth was temporized with Cavit (ESPE, Seefeld Oberb, Germany) and the patient was referred back to the referring dentist for the definitive restoration (Figures
(a) Initial radiograph, (b) final periapical radiograph (straight view), and (c) final radiograph (mesial view).
(a) Initial radiograph showing an access previously performed, (b) radiographic confirmation of the working length, (c) radiograph taken to check master cone, and (d) final radiograph.
A 37-year-old male patient was referred to the clinic of the one of the authors (Carlos Saucedo) for the endodontic treatment of his right maxillary second premolar. Treatment had been previously attempted at an endodontist’s office and was incomplete. The medical history was noncontributory. As the initial access had already been accomplished, thermal tests were not performed. The adjacent teeth exhibited unremarkable findings. Probing depths were within 3 mm. Preoperative radiograph demonstrated that access had been previously performed and a double curve or S-shaped anatomy (Figure
After administrating infiltration anesthesia (articaine 1 : 100.000 epinephrine) the rubber dam was placed; the previous temporary material was removed by using a 1016HL bur (Dentsply Maillefer, Ballaigues, Switzerland) and refinement of the access cavity was achieved using the Endo Z bur (Dentsply Maillefer, Ballaigues, Switzerland). As only one canal had been previously found toward the buccal aspect, the access preparation was extended toward the palatal side finding the palatal canal. Initial negotiation was performed with C+ .06 K files (Dentsply Maillefer, Ballaigues, Switzerland) 3-4 mm short of the radiographic apex. Irrigation with 17% EDTA was performed and the coronal two-thirds was flared using the TF System (SybronEndo, Orange, CA, EUA) starting with the .25/.10 file entering 3-4 mm into the orifice followed with the .25/.08 proceeding to 5–7 mm depths. Next, the Mini Apex Locator (SybronEndo, Orange, CA, EUA) was used to establish the working length which was also validated using a digital radiograph (Figure
After achieving the working length with a C+ 10 K file (Dentsply Maillefer, Ballaigues, Switzerland) the HyflexCM System was used (Coltene-Whaledent, Allstetten, Switzerland) finishing the instrumentation with a .30/.04 file. Blocking of the canal was prevented by using multiple recapitulations with a K file size .10 (Dentsply Maillefer, Ballaigues, Switzerland) between each rotary file use while copiously irrigating with 5% NaOCl using the Endovac irrigation system (SybronEndo, Orange, CA, EUA). The canals were flooded with 17% EDTA solution for 2 minutes and the canals were dried with size .20 sterile paper points and obturation was performed with the continuous wave of condensation technique [
Anatomical complexities and double curvatures have been reported by several studies [
The diagnosis and management of double curvatures, or S-shaped canals, present an endodontic challenge. Careful examination of preoperative radiographs is clinically helpful [
There is a consensus in the literature that instrumentation in curved canals considering a great degree of curvature predisposes higher risks of accidents [
In general, endodontics is a very complex discipline and an educational challenge for those institutions teaching the specialty. Studies have shown unsatisfactory endodontic treatments with preventable errors performed by undergraduate students [
Endodontic therapy is a very nuanced and challenging science and art. The clinical and teaching experience of the authors show different approaches that can be successfully employed to treat challenging teeth having roots with multiple curves. Technical principles of endodontic treatment require constant assessment, revisions, and definition.
Jorge Vera, in the past, has received honorarium from Sybronendo specialties. The other authors declare that there is no conflict of interests regarding the publication of this paper.