A novel approach to canal obturation

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The piston technique—a novel approach to canal obturation

The piston technique is a promising alternative to conventional obturation techniques. It can help endodontists achieve a 3D seal without the use of gutta-percha points and is particularly beneficial for challenging anatomical scenarios in root canals. (Image: VanoVasaio/Shutterstock; clinical images: Grzegorz Witkowski & Bartłomiej Karaś)

Up to now, the gold standard of obturation has been the continuous wave compaction technique.1,2 However, this technique is difficult to perform and needs additional expensive equipment. Another option is a newly reinvented technique of single-point obturation with calcium silicate-based sealers (CSBSs).3 Their properties are well known. In general, these materials are biocompatible, non-toxic, non-shrinking and chemically stable within the biological environment.4–7 They also have the ability to form hydroxyapatite during the setting process and to create a bond between dentine and the filling material.3,4 However, there is a lack of articles on this technique, and research has focused on point-less obturation techniques with CSBSs.8

In this article, we would like to present a new approach to obturation, the piston obturation technique, and share our clinical experience with it, recommending it for most clinical situations. The main benefit of this technique is that one achieves a 3D seal with no gutta-percha points. This is beneficial in cases of deep canal splits, ledges at apical areas, broken instruments in the apical third, and canal blockages and difficult anatomies in the apical zone.

Fig. 1.

Fig. 1.

The piston technique is simple and predictable. Once the final preparation and irrigation protocol has been performed, owing to the specific properties of CSBSs, the canal should not be overdried. A small amount of moisture should remain in the canal space as the catalyst for the setting reaction of the sealer. With the application needle introduced to the maximum level of the insertion, gently eject the material from the syringe directly into the canal space. To avoid extrusion, try not to block the needle in the canal. After seeing the material in the canal space, remove the needle and use a hot gutta-percha extruder to create a plug in the coronal part. Next, push the coronal part of the gutta-percha with the cold plugger towards the apical zone. Do not push more than 1–2 mm (Fig. 1).

Case 1

The patient was referred to Dr Witkowski’s dental office for endodontic treatment of teeth #31 and 41 (Fig. 2). After examination, endodontic treatment was performed (Fig. 3). In tooth #41, the access cavity was done by the referring dentist (Fig. 4a). In tooth #31, the access cavity was designed and performed (Fig. 4b). After this step, preparation of the canal space was done, in tooth #41 up to 25/0.04 and in tooth #31 up to 20/0.04 with VDW.ROTATE (VDW; Fig. 5). The next step was the irrigation protocol, which was performed with an Er,Cr:YSGG laser (BIOLASE) at 1.5 W and 100 Hz in both teeth. The canals were prepared for obturation. In tooth #41, obturation was done with a single point and CSBS, and in tooth #31, the piston technique was performed (Fig. 6). A control radiograph was taken immediately after the treatment (Fig. 7). Healing of the lesion was visible on the follow-up radiograph performed six months after the treatment (Fig. 8).
Fig. 7.

Fig. 7.

Fig. 8.

Fig. 8.

Case 2

The patient was referred to Dr Witkowski’s dental office for removal of a broken file in the mesial canal and the final endodontic procedure (Fig. 9). Owing to difficulties and the risk of perforation, bypassing of the file was suggested to the patient and she agreed. Proper instrumentation was performed in both the mesial and distal aspects using the R25 RECIPROC blue (VDW; Fig. 10). After this step, extensive irrigation protocol was performed with sonic agitation and continuous irrigation (Fig. 11). The root canal system was then prepared for obturation and obturated using the piston technique (Fig. 12). This technique is capable of obturating even not mechanically instrumented spaces and is very easy to use, especially when there is an obstacle in the canal space such as a broken file (Fig. 13).

Case 3

A deep split in the canal is always challenging, especially in situations where there is compromised access or limited space. The patient came to Dr Witkowski’s dental office for a routine procedure of caries removal and restoration (Fig. 14). An initial radiograph was performed (Fig. 15). Initial removal of caries was performed, and a gingivectomy was also done owing to a deep carious lesion in the subgingival area mesially (Fig. 16). After isolation, restoration of the mesial wall was performed according to the standard protocol. After this, the access cavity was reshaped with ultrasonic tips (Fig. 17).

Instrumentation was then performed with the R25 RECIPROC blue up to the level of the split, and the split was prepared with the 12.5/0.04 R-PILOT (VDW; Fig. 18). The final irrigation protocol was performed with copious amount of fluids (sodium hypochlorite and citric acid with a final rinse of distilled water; Fig. 19). Obturation was performed with the piston technique, and the restoration was done with composite material (Fig. 20). The patient was referred to the prosthodontist for final restoration. On the final CBCT scan, it was clearly visible that the piston technique had helped to obturate the deep split in the apical area (Fig. 21).

Case 4

The patient was referred to Dr Karaś’s office for non-surgical root canal retreatment of tooth #46. The tooth was symptomatic, and the radiographic examination revealed a periapical lesion around the mesial root. The periapical lesion was clearly visible, but the shape of the root canal was not clear (Fig. 22). The examination was extended by CBCT imaging. The CBCT scan revealed internal resorption in the mesiobuccal canal and an isthmus and apical inflammatory root resorption in the apical area of the mesial root (Fig. 23). A cast post and prosthetic crown were also noted.

Two treatment plans were presented to the patient, non-surgical root canal retreatment and surgical root canal retreatment. After intra-oral examination, the quality of the prosthodontic treatment was found to doubtful (Fig. 24). The decision was made to remove the crown and perform non-surgical retreatment.

After local anaesthesia, the crown was cut with a high-speed handpiece (Fig. 25). The post was exposed and removed (Fig. 26 & 27). The pulp chamber and root canal orifices were examined for cracks. After inspection, a gingivectomy was performed (Fig. 28) and a dental dam (Kerr Dental) was placed (Fig. 29). The dental dam was sealed with a temporary flowable material (Fig. 30). After sealing the dental dam, the full adhesion protocol with a sixth-generation self-adhesive primer and bonding agent was performed, and the pre-endodontic build-up was created (Fig. 31). Residues of the cement and root canal filling materials were removed with a diamond-coated ultrasonic tip (Woodpecker; Fig. 32). Patency was easily established with hand files (VDW), and the canals were shaped with rotary martensitic files (Poldent) up to 40/0.04. Each step of instrumentation was performed with lubricating cream containing EDTA (VDW; Fig. 33). After each instrument, the canals were flushed with 5.25% sodium hypochlorite (Cerkamed). After reaching the final sizes of the root canals, the irrigation protocol was performed: three sequences of 5.25% sodium hypochlorite and 40.00% citric acid (Cerkamed) activated with an ultrasonic file (MANI), followed by 5.25% sodium hypochlorite activated with the ultrasonic file for approximately 10 minutes (Figs. 34 & 35). The flow of the liquid between both mesial canals was visible.

At this stage, one of the most important decisions had to be made regarding the resorption and isthmus present in the mesial root. On the one hand, in the case of non-penetrating internal resorption, the material of choice is gutta-percha with a sealer. On the other hand, in the case of apical inflammatory root resorption, it is recommended to use mineral trioxide aggregate (MTA) or putty materials. There is no problem with using these two materials in the same root in most cases, but in this case, the canals were too narrow to use the MTA comfortably and the quality of filling of the isthmus that could be achieved was questionable.

From this point of view, a novel approach of placing a tricalcium silicate-based sealer was a promising idea. The sealer was placed in the previously described manner. The premixed sealer in the plastic syringe (Meta Biomed) was placed in the mesiobuccal canal and the syringe depressed until it filled the mesiolingual canal. The distal canal was filled separately. In each canal, pistons from the previously heated gutta-percha extruder were placed and the warm gutta-percha was slightly compacted with stainless-steel hand condensers. A periapical radiograph was taken to evaluate the quality of the obturation. The bioceramic sealer was slightly extruded through the resorbed apex into the periapical area (Fig. 36). After the obturation, the chamber and orifices were cleaned (Fig. 37). A resin core with fibre posts was placed, and the temporary pink material was removed. The patient was referred to the prosthodontist for final restoration.

The recall appointment was performed after three years. The periapical radiograph and CBCT scan revealed healing of the periapical tissue and no resorption of the bioceramic sealer (Fig. 38). The tooth remained asymptomatic.


The piston technique suggested in this article is a predictable and efficient method of obturation of the canal space. It requires further research and discussion; however, it appears to be especially promising in compromised cases with difficulties such as complex anatomy, foreign objects or procedural errors during initial treatment.

Editorial note:

This article was published in roots—international magazine of endodontics vol. 19issue 2/2023. The list of references can be found here.

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