Endodontic Management of a Severely Curved Mandibular Second Molar with Modified Double Flared Technique, Report of a Case

Endodontic Management of a Severely Curved Mandibular Second Molar with Modified Double Flared Technique, Report of a Case
Arshad Hasan* , Maryam Ali**

* Assistant Professor, Operative Dentistry Department. Hamdard University, Karachi ** Demonstrator, Operative Dentistry Department, Hamdard University Karachi
Correspondence: Dr. Arshad Hasan

How to CITE:

J Pak Dent Assoc 2010;19(1): 54-57


Exaggerated curvatures of root canals have historically been difficult to treat. The present case report deals with one such case. A 40 year old male presented with signs and symptoms of pulpal pathosis in right lower second molar. Pre operative radiograph revealed an exaggerated curvature of mesial roots. The case was treated with ISO standerdized NiTi manual files using the modified double flared technique. Patient came back for a recall visit after a year and was symptomless.


Canal curvature, NiTi files, modified double flared technique.


Complete cleaning and shaping of the entire pulp canal system and its Obturation in all dimensions is essential for a long term clinical success of root canal therapy. Canal curvature presents a most frequent obstacle in achieving the above mentioned objectives.1

According to Weine, management of a canal with a curvature of more than 60 degree is technically very difficult.2 Endodontic management of such abrupt and severe curvature requires expert handling for complete debridement. Introduction of rotary NiTi instruments in 1993 brought a revolution in the management of curved canals.3 The NiTi instruments have resulted in ease of negotiation of curved canals and an extremely decreased frequency of iatrogenic complications. However, the use of NiTi rotary instruments is inappropriate in abrupt and severely curved canals. Also, the cost of NiTi rotary systems makes their use prohibitive in most of population of a developing country. In such cases use of much cost effective manual NiTi instrumentation with a special canal shaping technique may be of more value.1 Modified double flared technique is one of the manual canal preparation techniques described in the literature.4

Fava introduced the double flared technique in 1983.5 The technique involves the use of straight files in a larger to smaller sequence until apical third is reached. Working length is established and larger to smaller files are used again in a crown down manner until working length is reached. This is the end of first flare from coronal to apical direction. The second flare consists of stepping back and merging the apical preparation with the coronal one.6

Saunders and Saunders further refined this technique and used non-cutting tipped flexible instruments with balanced force instrumentation action and renamed it as modified double flared technique.7 Fava showed that the incidence of post operative pain with this technique in single visit cases was comparable to other techniques.8


Bishop and Dummer reported that manual NiTi files produced better shapes than stainless steel files when both were used with modified double flared technique in curved canals.9 The case report presented here describes the use of modified double flared technique with manual NiTi files in the endodontic management of a severely curved mandibular second molar.


A 40 year old male presented to the department of operative dentistry, Hamdard University dental hospital with a complaint of food lodging in his right lower second molar. History revealed that the tooth felt jolt on taking cold water which subsided immediately after withdrawal of stimulus. Radiograph examination showed a deep carious lesion and intact periodontium with sharp curvature of roots (Fig no 1). A diagnosis of reversible pulpitis was established and a restoration was planned for the second molar. However, upon caries excavation, pulp was exposed and a direct pulp cap was performed. Patient returned after a week complaining of severe and lingering

temperature sensitivity, characteristic of irreversible pulpitis. The patient was immediately referred to endodontic department for the management where a decision was made to perform an endodontic procedure.


After taking an informed consent, local anesthesia (Xylocaine 2% with epinephrine 1:100,000) was administered. An inferior dental block, Lingual nerve block and a long buccal infiltration was given. Rubber dam was placed and a standard access cavity was prepared with round bur. Three orifices were located, two on mesial side and one on distal side. Due to the presence of acute curvature in mid third of root, it was decided to use the modified double flared technique with ISO tapered NiTi hand files (Nitiflex, Dentsply Switzerland). Initially a no. 10 ss (stainless steel) file was used to confirm the patency of canal. The file had to be pre bent considerably due to canal anatomy. Canal was irrigated with 5.25% sodium hypochlorite after every insertion of a file. A no. 40 nitiflex file was inserted in the canal and used with balance force technique as described by Roane and Sabala. File was inserted to resistance and rotated clockwise in a 450-900 degree arc without apical pressure. It was then rotated 90 degree counterclockwise with apical pressure. File was again rotated clockwise with an audible click and was withdrawn from canal. Successively smaller files were used similarly until curvature was approached. Gates Glidden drills were used in a slow speed contra angle handpiece in an anti-curvature manner. These drills were used in a step back fashion from no. 1 to no 4 upto the curvature. A no. 10 ss file was than worked up to approximate working length. The file was again pre bent considerably due to canal anatomy. Once the no. 10 file became loose, a prebent no. 15 ss file was taken to approximate length and a working length radiograph was

exposed (Fig no 2).After establish the working length nitiflex files were again used in a crowndown fashion with balance force movement until working length was reached. A prebent no. 10 ss file was used after each insertion of nitiflex file to ensure patency. The nitiflex files were then stepped back in a balance force motion after a master apical size of 25 was reached. Canal was then dried with paper points and obturated with laterally condensed gutta percha. ISO tapered gutta percha and finger spreaders were used with a calcium hydroxide based sealer (Sealapex, SybronEndo USA) (Fig no 3). The access cavity was restored with amalgam and patient was referred back to the department of operative dentistry for crown placement.


Patient returned symptomless after a week. Crown preparation was performed and impression was send to laboratory. A metal crown was placed 2 weeks later. Patient returned for follow up visit a year later and the tooth was clinically and radiographically healthy. (Fig no 4).


p>The case presented in this study exhibited a severe curvature. The preoperative curvature of canals as determined by Weine’s method, was 100°.2 Management of severely curved root canals requires an exceptional set of skills along with special set of instruments.11 The introduction of rotary NiTi brought a revolution in management of curved root canals. However, their use in severe and abrupt curvature is still not recommended even after more than a decade of research.12 In such cases manual NiTi instruments are preferred over stainless steel instruments, due to superelasticity and shape memory.9 It has been proven beyond doubt that the stainless steel hand instruments are responsible for most of iatrogenic mishaps, namely ledge, zip, transportations and perforations.13,14,15 It was because of these reasons, NiTi hand files were used to treat the difficult anatomy in the present case.


NiTi hand instruments can be grouped into two categories on the basis of taper. ISO tapered and non-ISO tapered. The ISO tapered NiTiflex hand files were used in the case presented in this report since they are cost effective and it has been shown that they are comparable to non-ISO tapered hand files in shaving curved canals.16


Modified double flared technique was used to treat the severely curved anatomy of lower second molar in this report. This technique was initially introduced by Fava and was further modified by saunders and Seunders.5,7 The technique utilizes balanced force movements introduced by Roane and Sabala in 1985.10 The benefits of balance force technique are numerous. Files remain centered

within the canal and thus there is no transportation. There is no blockage due to debris since the flutes of files become loaded with dentine shaving. Another reason for not blocking the canals is the directions of movements of files which is circular as opposed to push and pull which is more prone to canal blockade.17 The technique is used in a crown down fashion which further facilitates early coronal canal enlargement and early movement of irrigants into apical third


  1. A preoperative radiograph should always be assessed before starting any endodontic procedure in order to detect difficult anatomy.


  1. Use of manual NiTi files may be of more value in treating complex endodontic cases. The cost of manual NiTi files is much less than rotary NiTi systems and thus affordable for most of general dentists.


  1. Moreover, cases with difficult anatomy should be referred to endodontists, who boast skills and tools necessary for negotiating such complex cases.


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2. Weine FS. Endodontic Therapy, 5th edi. St. Louis. Mosby-Year Book, Inc. 1996:305-394.

3. Serene TP, Adams JD, Saxena A. Nickel-Titanium instruments: applications in Endodontics. St. Louis: Ishiaku EuroAmerica; 1995.

4. Al Negrish AS, Al Shanti D Incidence Of Post Obturation Pain Related To Two Root Canal Hand Preparation Techniques: A Prospective Clinical Study. Pak Oral dental J, 2009 ; 29:99-106.

5. Fava LR. The double-flared technique: an alternative for biomechanical preparation. J Endod. 1983 ;9:76-80.

6. Glickman GN, Dumsha TC, Problems in Canal Cleaning and
Shaping. In: Gutmann JL, Dumsha TC, Lovdahl PE, Hovland
EJ editors. Problem Solving in Endodontics. St. L o u i s :
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8. Fava LR.Single visit root canal treatment: incidence of postoperative pain using three different instrumentation techniques. Int Endod J. 1995 ;28:103-107.

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Flexofiles and nickel-titanium NiTiFlex files during the s h a p i n g of simulated canals. Int Endod J. 1997;30:25- 34.

10. Roane JB, Sabala CL, Duncanson MG. The balanced force Concept for instrumentation of curved canals. J Endod 1985;11:203-211.

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14. Royal JR, Donnelly JC. A comparison of maintenance of canal curvature using balanced-force instrumentation with three different file types. J Endod. 1995 ;21:300-304
AM.Comparative study of six rotary nickel-titanium systems and hand instrumentation for root canal preparation. Int Endod J. 2005 ;38:743-752.

16. Song YL, Bian Z, Fan B, Fan MW, Gutmann JL, Peng B. A comparison of instrument-centering ability within the root canal for three contemporary instrumentation techniques. Int Endod J. 2004 ;37:265-271.

17. al-Omari MA, Dummer PM Canal blockage and debris extrusion with eight preparation techniques. J Endod. 1995 ;21:154-158.


Author’s: Dr. Walid Abdullah / Dr. Hesham Khalil / Manal A.AlShedd
Issue Decription: Volume 18 Issue No.4 Oct-Dec2009
Page No. 146-150