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Year : 2022  |  Volume : 25  |  Issue : 5  |  Page : 573-577
A simple predictable triple protocol for the management of double-curved canals (Case report of three cases)

Department of Restorative and Endodontics, Faculty of Dentistry, University of Damascus, Damascus, Syria

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Date of Submission17-May-2022
Date of Decision27-May-2022
Date of Acceptance07-Jun-2022
Date of Web Publication12-Sep-2022


Double-curved canals, despite their rarity, pose a great challenge to complete endodontic treatment, and the difficulty lies in negotiating these canals and reaching their apex, whereas the greatest difficulty lies in their shaping, disinfection, and obturation. Conventional methods require excessive preflaring to the level of the first curvature to facilitate access and handling of the second one. Modern technologies facilitate dealing with these cases without compromising the dental tissues, metal alloys have become more flexible, and activation techniques have made it possible to deliver irrigants deeper. The triad of minimum shaping with tactile-controlled activation technique, hybrid irrigation, and sealing with bioceramics constitute an integrated and effective method to deal with these cases, and this protocol was used in the following three cases.

Keywords: Bioceramic sealing, hybrid irrigation, tactile-controlled activation

How to cite this article:
Seirawan MY. A simple predictable triple protocol for the management of double-curved canals (Case report of three cases). J Conserv Dent 2022;25:573-7

How to cite this URL:
Seirawan MY. A simple predictable triple protocol for the management of double-curved canals (Case report of three cases). J Conserv Dent [serial online] 2022 [cited 2022 Sep 25];25:573-7. Available from:

   Introduction Top

The success of endodontic treatment depends on the mechanical and chemical debridement of the root canals to clean their contents and reduce the bacterial load.[1]

However, regarding the double-curved canals that are rarely encountered, preservation of the original canal shape is an important principle in minimum conservative dentistry. Therefore, conservative shaping of the canals is essential to avoid the possibility of ledges, perforations, and transportation of the apexes.[2],[3]

After negotiating the canals to reach their apexes, using the watch winding and repeated pecking motions, the rotational shaping of the canals remains one of the greatest challenges. The tactile-controlled activation (TCA) technique was introduced by Antonis Chaniotis as an innovative recommended technique to be used with controlled memory files to perform safe instrumentation, especially in severely curved canals.[4]

Chemical irrigation plays the most important role in canal disinfection, as irrigants must reach most of the ramifications of the canal system for effective cleanliness,[5] and due to the limited flow of irrigants beyond the needle tip, there is an urgent need to agitate the irrigants using ultrasonic/sonic tools to maximize their accessibility and efficiency.[6]

The double curvature of the canal obstructs the entry of the metallic irrigation tip and even the rigid ultrasonic tip. Therefore, the sonic activation tips are ideal and convenient tools to reach the farthest level of the curvature safely and effectively.

Recently, the introduction of biocompatible materials enables to secure a hydraulic sealing without inserting large instruments of warm vertical compaction inside the canal.

Bioceramic materials in premixed consistency have high flowability and low viscosity, making their texture ideal for sealing root canals. It is used with a gutta-percha point, which is mainly used as a piston to deliver it hydraulically into the main and accessory canals as well as root canal irregularities.[7]

The current report shows three complex cases with double-curved canals treated with the previous triple protocol, which showed beneficial, safe, and predictable results.

   Case Reports Top

Case 1: Double-curved canals in the mesial root of the mandibular first molar

A 32-year-old male patient came to the department of endodontics with a chief spontaneous pain in the lower right area related to the right first molar (tooth #46). X-ray confirmed the absence of any deep caries, the main reason was the gingival recession, and the application of anti-sensitive materials was carried out several times without benefit. The decision was taken to perform a root canal treatment. The treatment technique was explained to the patient and his consent was obtained. After opening the pulp chamber and following the floor map, four orifices were detected; two in each root, mesial canals were negotiated to full working length with verifying by electronic apex locator, and two canals were fused in the apical part as a Type 2 of Weine's classification of root canal morphology; the shape of manual K-files after canal traversal indicated the double-curved anatomy.

Instrumentation protocol

Tactile-controlled activation technique

This technique is useful in complex cases such as a severe abrupt curvature to take advantage of the (controlled memory files, heat-treated files, and electrical discharged machined files) which have high fatigue resistance and high flexibility. Precurved nonactivated files are inserted passively inside the canal until frictional resistance is felt, the file is activated and pushed apically (in-stroke) until it confronts further resistance, then it is pulled out (outstroke), cleaned, and inspected for any possible deformation. Copious irrigation and patency are frequently confirmed to preserve the original path of the canal, then the same file is inserted again in the same way deeper and closer to the apex.[4]

The glide path of each canal was maintained using HyFlex Electric Discharge Machining (EDM) Glide Path File (#10/0.05, Speed = 300 rpm, Torque = 1.8 Ncm) (Coltene-Whaledent, Altstatten, Switzerland) using TCA technique; where mesiolingual canal was glided to the full working length, whereas mesiobuccal was glided to the conjunction level, then the distal canals were easily glided.

Manual K-files #08–10 (M-access; Dentsply Maillefer, Ballaigues, Switzerland) were used with lubricating by ethylenediaminetetraaceticacid (EDTA) gel (MD-ChelCream, Meta Biomed Co., Ltd., Cheongju City, Chungbuk, Korea) to check apical patency after each path-file stroke.

Shaping of the mesial canals was performed using HyFlex EDM Preparation File (#20/0.05, Speed = 500 rpm, Torque = 2.5 Ncm) (Coltene-Whaledent, Altstatten, Switzerland) with TCA technique, whereas HyFlex EDM One File (#25/~, Speed = 500 rpm, Torque = 2.5 Ncm) (Coltene-Whaledent, Altstatten, Switzerland) was additionally used to finish the preparation in the distal canals.

Hybrid irrigation protocol

Sodium hypochlorite 5.25% was used with liquid of EDTA 17% using side-vented needles of irrigation (Steri Irrigation Tips: DiaDent, Korea) in constant up and down motion.

After every 5 ml of irrigation, ultrasonic activation is done for 15 seconds using stainless steel ultrasonic tips (#20/0.02) (IrriSafe, Satelec Acteon, France) connected to an ultrasonic handpiece (Suprasson P5 Booster, Satelec Acteon, France) before 1 mm had double curvature abnormal of the level of curvature without touching of the canal walls to enable free vibration of the tip. Sonic activation is done for 15 s using elastic polymer tips (#15/0.02) (EQ-S; Meta Biomed, Cheongju, Korea) before 2 mm of the working length, according to the clinical protocol suggested previously since the flexible polymer tips have more ability to reach deeper than stiff stainless steel ultrasonic ones.[8]

Obturation with bioceramics

All prepared canals were fully filled by calcium silicate-based sealer “Bioceramic” (CeraSeal; Meta Biomed, Cheongju, Korea) with a single cone #20/0,4 in the mesial and #25/0,4 in the distal canals availing the hydraulic condensation feature [Figure 1]a, [Figure 1]b, [Figure 1]c.
Figure 1: Double-curved canals in the mesial root of the mandibular first molar (a) before treatment, (b) cone fit, and (c) mesial view of the obturation

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The tooth was completely restored by resin composite, and then the follow-up session revealed the disappearance of all previous symptoms.

Case 2: Severe double-curved canal in the mesial root of the mandibular first molar

A 37-year-old male patient was referred to the department of endodontics with a story of uncomfortable feeling in the lower-left area. The lower first molar (tooth #36) was the last unit in three-unit precious bridge, and his response to percussion was very painful. Same technique was suggested to the patient and his consent was performed. After clinical and radiographic examination, access cavity was performed through the crown using round diamond bur, after strict isolation by a rubber dam.

After refinement of the access cavity, four orifices were found, then old gutta-percha was removed using ProTaper Universal-retreatment files D1-D2 at speed of 600 rpm and torque of 3 Ncm (Dentsply Maillefer, Ballaigues, Switzerland) with copious irrigation. Mesial canals were hardly negotiated to the apical foramen, and glide path was confirmed manually using a lot of K-files #08–10. HyFlex EDM Glide Path File was used again in TCA technique to obtain the glide path in the separated mesial canals and the fused distal canals, then HyFlex EDM Preparation File (#20/0.05) was used alone to prepare the mesial canals in TCA motion, while HyFlex EDM One File (#25/~) was additionally used in the merged distal canals. Hybrid irrigation protocol was used again with NaOCl 5.25% and EDTA 17% in the same details that abovementioned.[8] All canals were fully filled by bioceramic sealer with #20/0,4 single cones in the mesial canals and #25/0,4 cones in the distal canals, whereas additional cones were condensed laterally in the distal canal [Figure 2]a, [Figure 2]b, [Figure 2]c. The patient was asymptomatic at the follow-up visit.
Figure 2: Retreatment of double-curved canals of the mandibular first molar (a) before treatment, (b) parallel view of the obturation, and (c) distal view of the obturation

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Case 3: Severe double-curved canals in the upper second premolar

A 51-year-old male patient was referred to the department of endodontics to continue root canal treatment initiated with a general dentist, and upon radiographic examination, the root of the second maxilla premolar had double curvature abnormal morphology (tooth #25). The decision was taken to do endodontic treatment in one visit with the same protocol and consent was confirmed. Buccal canal was hardly negotiated to the full working length, then the glide path was confirmed manually using a lot of K-files #06–08 with plenty of lubricants to facilitate the use of rotary files. Lingual canal was easily achieved because it was fused with the buccal canal apically.

HyFlex EDM Glide Path File was used to confirm the glide path of the canals using TCA technique with copious irrigation and activation, and then HyFlex EDM Preparation File (#20/0.05) was used again alone to prepare both two canals. Hybrid irrigation protocol was performed again to disinfect the canals and remove residues as much as possible.[8] All canals were fully filled by bioceramic sealer with #20/0,4 single cone technique [Figure 3]a and [Figure 3]b. All symptoms were released at the follow-up visit.
Figure 3: Severe double-curved canals in the maxillary second premolar (a) before treatment and (b) after obturation

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   Discussion Top

Most of the complicated root canals are challenging to treat without deformity of anatomy and the risk of file separation.[4] Hence, the tactile-controlled activated TCA technique was used in the previous cases to avoid the possibility of file separation and transportation of the canals and ledges caused by continuous conventional rotation.

Sodium hypochlorite 5.25% is the most effective irrigant for eliminating bacterial biofilm from the root canal, in addition to EDTA 17% which removes the smear layer.[9]

The double curvature is a real challenge which impedes the entry of the irrigation needle and thus reduces the delivery of liquids, which are never delivered more than 0–1.1 mm beyond the needle tip under ideal conditions.[10]

Ultrasonic and sonic agitation increases the effectiveness of debris and smear layer removal.[11]

Passive ultrasonic irrigation has a high rate of oscillation frequency (25–30 kHz) which increases irrigants penetration almost to the working length,[10] by virtue of acoustic microstreaming and cavitation along the length of the ultrasonic tip, but at the same time, it negatively affects the canal walls when it touches them due to its wide amplitude.[12]

Sonic activation operates at a lower frequency (1–6 kHz), in spite of that the sonic tip generates high amplitude and greater back-and-forth movement,[6] and when the oscillation of the tip is constrained, it will change to a longitudinal oscillation.[13]

Hybrid irrigation is built on availing the advantages of both types and avoiding their negative effects since the double-curved canals are very narrow in the most cases, the ultrasonic tips have an impossible chance of going beyond the level of curvature because they can straighten the canal's path and can make a ledge or at least can break off inside the canal. However, hybrid activation has demonstrated excellent results of cleanliness in previous studies.[8]

Although the apical enlargement increases the volume and efficiency of the irrigants and thus reduces the bacterial load at the apical level, especially in the infected canals,[14] the canals must be preserved as its initial original morphology to avoid any complications such as tearing, zipping, or transportation,[2] and this is what was adopted in the current cases; where the minimum shaping of canals was limited to 0.20.

Historically, there has been no definitive determination of the apical size, so the enlargement of the apical foramen remains a controversial issue, as someone has argued that the minimum size for it is about 0.35 or 0.40, but someone claimed that enlarging it to 0.25 was enough and effective.[15]

New ultrasonic/sonic activation techniques can facilitate the reaching ability of the irrigants and increase the efficacy of them in the minimum enlarged canals, and it is certain that the irrigants will be able to reach the end of the canal as long as the sealer and the gutta-percha cones have reached.

One of the most important basics for successful treatment is the appropriate tight sealing of the canal system which diminishes microorganisms and that can be achieved with bioceramics which are innovative user-friendly materials designed with superior mechanical and biocompatible properties. They are hydrophilic materials that need moisture to set and harden, also are insoluble, and have a high pH.[7]

Bioceramic can be used with a single-cone technique as an adequate option for obturation.[16] Moreover, this hydraulic condensation method was adopted in the three current cases due to the narrowness of the canals and their extreme double curvature, and because the thermal techniques of obturation require large tips that cannot reach beyond the depth of the curvature level.

In addition to that, the bonding of the bioceramic sealer eliminates the microleakage of microbes if there is any lack of coronal seal,[7] that leads to long-term success.

   Conclusion Top

The current triad protocol of TCA technique, hybrid irrigation, and biocompatible sealing demonstrated a simple, safe, and effective protocol to perform root canal treatment in complex double-curved cases.


The author would like to thank Clinics in the Faculty of Dentistry, Damascus University.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Vertucci FJ, Haddix JE, Britto LR. Tooth morphology and access cavity preparation. In: Cohen S, Hargreaves KM, editors. Pathways of the Pulp. 9th ed. Louis, MO, USA: Mosby; 2006. p. 148-232.  Back to cited text no. 1
Peters OA. Current challenges and concepts in the preparation of root canal systems: A review. J Endod 2004;30:559-67.  Back to cited text no. 2
Jafarzadeh H, Abbott PV. Ledge formation: Review of a great challenge in endodontics. J Endod 2007;33:1155-62.  Back to cited text no. 3
Chaniotis A. Tactile controlled activation technique with controlled memory files. Endod Pract US 2016;9:31-6.  Back to cited text no. 4
Boutsioukis C, Lambrianidis T, Kastrinakis E. Irrigant flow within a prepared root canal using various flow rates: A Computational Fluid Dynamics study. Int Endod J 2009;42:144-55.  Back to cited text no. 5
Gu LS, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of contemporary irrigant agitation techniques and devices. J Endod 2009;35:791-804.  Back to cited text no. 6
Debelian G, Trope M. The use of premixed bioceramic materials in endodontics. G Ital Endod 2016;30:70-80.  Back to cited text no. 7
Yaman Seirawan M, Layous K, Kinan Seirawan M, Doumani M. Removal of double antibiotic paste and calcium hydroxide from simulated models of regenerative endodontic procedures using several protocols of irrigation: In-vitro comparison study. J Stomatol 2021;74:1-8.  Back to cited text no. 8
Soares JA, Roque de Carvalho MA, Cunha Santos SM, Mendonça RM, Ribeiro-Sobrinho AP, Brito-Júnior M, et al. Effectiveness of chemomechanical preparation with alternating use of sodium hypochlorite and EDTA in eliminating intracanal Enterococcus faecalis biofilm. J Endod 2010;36:894-8.  Back to cited text no. 9
Munoz HR, Camacho-Cuadra K. In vivo efficacy of three different endodontic irrigation systems for irrigant delivery to working length of mesial canals of mandibular molars. J Endod 2012;38:445-8.  Back to cited text no. 10
Urban K, Donnermeyer D, Schäfer E, Bürklein S. Canal cleanliness using different irrigation activation systems: A SEM evaluation. Clin Oral Investig 2017;21:2681-7.  Back to cited text no. 11
Plotino G, Pameijer CH, Grande NM, Somma F. Ultrasonics in endodontics: A review of the literature. J Endod 2007;33:81-95.  Back to cited text no. 12
Walmsley AD, Lumley PJ, Laird WR. Oscillatory pattern of sonically powered endodontic files. Int Endod J 1989;22:125-32.  Back to cited text no. 13
Brunson M, Heilborn C, Johnson DJ, Cohenca N. Effect of apical preparation size and preparation taper on irrigant volume delivered by using negative pressure irrigation system. J Endod 2010;36:721-4.  Back to cited text no. 14
Saini HR, Tewari S, Sangwan P, Duhan J, Gupta A. Effect of different apical preparation sizes on outcome of primary endodontic treatment: A randomized controlled trial. J Endod 2012;38:1309-15.  Back to cited text no. 15
Chybowski EA, Glickman GN, Patel Y, Fleury A, Solomon E, He J. Clinical outcome of non-surgical root canal treatment using a single-cone technique with endosequence bioceramic sealer: A retrospective analysis. J Endod 2018;44:941-5.  Back to cited text no. 16

Correspondence Address:
Dr. Mohammad Yaman Seirawan
Department of Restorative and Endodontics, Faculty of Dentistry, University of Damascus, Al-Mazzeh St., Damascus 30621
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_289_22

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