Dental Tribune International

From a distal

By Dr Sam Alborz, USA
January 26, 2017

Limited workspace is a common problem in endodontic treatments. Before the arrival of pre-bendable NiTi files, a lot of RCT’s seemed to be almost inexecutable due to severe constraints in the access area. The following three cases illustrate how modern endodontic instruments help specialists to enter a new era of canal preparation, particularly if the apex is comparatively hard to reach. Standard endodontic treatment begins with placement of a dental dam to isolate the working environment, access to the canal via opening of the pulp chamber, and gauging the correct working length using a state-of-the-art electronic apex locator. However, root canals often come in extraordinary shapes: an unusually curvy anatomy with hidden accessory canals or horizontal branches might pose a real challenge to the most experienced of endodontic experts.

If the tooth is in a remote position or craniomandibular problems are added to the picture, the task is even more difficult. Thankfully modern endodontics offers practitioners a whole range of clever instruments and dental materials that ensure an effective and reliable preparation and filling of the canal system. This is good news to endo-specialists given that not all cases allow standard procedures – or following the words of the old Bette Midler song: sometimes the world looks different ‘from a distal’.

Case presentation
Necrosis in S-shaped canals
In our first case, a 23-year-old male patient was referred to our dental practice with chief complaint of pain in the lower left mandible. The radiograph showed deep caries approaching the pulp chamber and clinical testing revealed a diagnosis of irreversible pulpitis with symptomatic apical periodontitis (Fig. 1). Further review of the radiographs showed that tooth 18 had a very complex anatomy of the mesial roots: the canal system was almost S-shaped and the apex therefore would be difficult to reach. In addition to the distinct mesial-distal curvature there was a significant faciolingual curvature associated with the mesial roots which was discovered during hand intrumentations. Yet, the difficult anatomy of the root canal system itself was not the only constraining factor that considerably narrowed work space. To make things even more challenging, the patient had a severe class II skeletal relationship. Together with the posterior position of the offending tooth, this combination limited access to the canal openings even further.

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The insufficient interocclusal space did not allow a common NiTi 21 mm rotary instrument to fit into the canal. For this reason, a special NiTi file system by Swiss dental specialist COLTENE was used for canal preparation. The HyFlex EDM is a modular designed nickel titanium file system: in close cooperation with leading universities and international endo-specialists, the renowned research department of the company developed an extremely versatile concept which meets various demands. The abbreviation ‘EDM’ stands for a specific manufacturing process named ‘Electrical Discharge Machining’, which produces a unique surface (Fig. 2). The spark erosion employed improves cutting performance, as the created structure can be compared with the serrated edge of a knife you use for cutting bread at home. Due to its special material properties, the file is virtually unbreakable and predestined for dentists who require fast and reliable results using a reduced file sequence.

In the case described we benefitted first and foremost from the so-called ‘Controlled Memory’- effect (CM): similar to classical stainless steel files, HyFlex files can be pre-bent and considerably help in preparation of distal molars (Fig. 3, 4). At the same time they do not bounce back like classic NiTi files, which means that they move in an optimal way in the centre of the canal. During autoclaving, reusable CM-treated files return to their initial shape because they are not plastically deformed. Due to the special situation of the patient the pre-bent EDM files were the only files that would fit in the limited work space. Interestingly, the 25 mm EDM file fit in a space that would not allow a 21 mm traditional rotary NiTi.

To create a suitable glide path, both mesiobuccal and mesiolingual canals were handfiled to a size 15 file. All pulpal tissue was removed after opening the pulp chamber and canal clearance was checked thoroughly. For the actual preparation, the use of a universal EDM file in ISO size 25 totally sufficed (Fig. 5). With the flexible file we were able to instrument the mesial canals to a working length of 22 mm. Keeping its pre-bent shape, the instrument permitted to work without any stress and when the apex was gauged in the distal canal, a size 30 hand file seemed to fit in quite comfortably. Consequently, a 40/0.04 HyFlex EDM finishing file was used to enlarge the apical aspect of the two distal canals. It is important to point out that thorough irrigation was performed with sodium hypochlorite between every file. At the end of the procedure the canals were irrigated with NaOCI, EDTA and CHX under acoustic streaming. The canals were then dried via microsuction followed by the insertion of the corresponding paper points. In the end, the canals were obturated with the help of the traditional warm vertical compaction technique (Fig. 6).The pulpal floor was sealed with a layer of glass ionomer, sponge pellet (to act as a spacer) and a dualcured temporary filling material consisting of zinc oxide and zinc sulphate over the top. A post- op radiograph was obtained (Fig. 7) and after the successful endodontic treatment the patient was subsequently referred to his general dentist for the definitive restoration of the tooth.

Abrupt canal curvature
Our second case proved to be equally challenging: a 24-year-old female patient entered our referral practice with a necrotic pulp in tooth 18. The opening was limited and once again, the tooth was positioned very distal with only limited space for instrumentation. The root canals were highly curved with sudden sharp dilacerations (Fig. 8). After consultation, the patient agreed to root canal treatment.

The dental dam was used to isolate the tooth and the canals were accessed with a round diamond bur. The previous composite resin restoration was removed to facilitate the identification of possible cracks. The dentin appeared to be intact, we then proceeded to shape the canals. We started to handfile all canals to a size 15 hand instrument to create a suitable mechanical glide path. In the following sequence all files were pre-bent beginning with HyFlex EDM 10/0.05 (Fig. 9), followed by the EDM OneFile size 25 in a soft pecking motion. Thorough irrigation throughout the treatment helped clear the canals of any debris and necrotic tissue. Gauging the apices revealed ample enough room for a size 30 hand file, indicating that apical enlargement was warranted. The decision was made to utilise EDM 40/0.04 finishing file on the distal canals. Due to the abrupt canal curvature, the mesial canals were shaped using a HyFlex CM 35/0.04. After copious irrigation with NaOCI, EDTA and CHX under acoustic streaming the canals were dried and obturated using the warm vertical compaction technique. Thanks to the flexible, fracture resistant files we were able to shape the canals very effective and efficiently. The access was closed in the same manner as in case 1 (see Fig. 10, 11). Without pre-bendable NiTi files, we would probably have been unable to perform root canal treatment on this tooth.

Size 60 finishing files
In our last case, a 37-year-old female patient presented with a necrotic pulp in the upper right central incisor with an evident vestibular swelling (Fig. 12). The pulp chamber was accessed using a surgical length friction grip size 2 round bur. Once working length was obtained the canal was hand filed to a size 15 hand instrument. Additionally, the HyFlex EDM Orifice Opener 25/0.12 was used to enlarge the coronal aspect of the canal. The apex was gauged, showing that a size 50 hand file was snug. As the canal was already very large coronally, we decided to use a size 60/0.02 EDM finishing file to shape the remainder of the canal and accomplish apical enlargement (cp. Fig. 13). Even the large size 60 EDM file proved its astonishing fracture-resis-tant quality throughout this case (Fig. 14).The canal was irrigated with NaOCl, dried, calcium hydroxide applied, and sealed with a provisional restoration. To alleviate vestibular swelling incision and drainage was performed.

Three weeks later the patient returned for her follow-up visit. The swelling and I & D site had fully resolved. The root canal system was irrigated, obturated, and sealed as described in the previuos cases and the patient was referred back to her general practitioner (Fig. 15). With the aid of the HyFlex EDM fi les we were able to complete the entire treatment using only two rotary instruments. With this effective system we were able to stay conservative coronally yet enlarge apically. With the right equipment both root canal specialists and general practitioners can create convincing results in a short period of time, without making any concessions to the natural anatomy of the root canal.

Modular designed NiTi systems demonstrate their full versatility in root canal profi les that are diffi cult to access or have an unusually abrupt curvature. Flexible files like the HyFlex EDM or HyFlex CM can be prebent, which helps dentists to operate both confi - dently and safely, even under challenging conditions. Depending on the clinical situation endo-specialists can choose between fast instrumentation with only a few fi les or high-precision shaping of the canal with a clever combination of a more refi ned fi le sequence. Thanks to their intuitive way of handling even newcomers to endodontics can achieve reliable results in next to no time – with an astonishing ‘distal effect’.

Editorial note: This article was published in roots international magazine of endodontics No. 03/2016.

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