The importance of irrigation in challenging cases

Introduction

Irrigation of root canals is key to improving the removal of bacteria, pulp tissue, the smear layer and debris from the root canal system, reducing the risk of post-treatment disease. In fact, it is well known that mechanical instrumentation leaves untreated canal areas ranging from 10 to 50% in individual canals. In these areas, there is the possibility for bacteria to replicate, leading to the failure of the treatment. A recent article showed that the bacterial persistence at the time of lling has a significant inuence on the outcome of the treatment, regardless of the irrigating solution and the medication used, thus stressing the importance of eradicating as many microorganisms as possible from the root canal system. The synergy between mechanical preparation and irrigation is inuenced by several factors, such as the uid properties and the volume of the irrigant, the irrigant delivery system and its depth of placement, and the anatomy of the root canal system.
Conventional needle irrigation is unable to provide good disinfection because of the risk of the vapour lock effect and because needles can have difculty penetrating into narrow spaces; as a consequence, the difculty in reaching the most apical region of the canal with large volumes of fresh irrigant may result in insufcient replacement and uid exchange beyond the tip of the needle. In order to increase the efciency of the irrigation, the literature suggests the use of preheated solutions or activation of irrigants1 by means of ultrasonic/sonic devices or negative pressure devices.
The closer the needle is to the working length, the greater the irrigation is. For this reason, using products that follow the anatomy of the prepared root canal can help in this clinical step. However, the ux must not be violent, in order to decrease the risk of extruding debris into the periapical tissue.
Several articles have described the use of a novel polypropylene needle (IrriFlex, Produits Dentaires) characterised by a back-to-back side vent design that helps the clinician irrigate the root canal space efciently and safely. This product, with its 30-gauge tip, has the advantages of reaching the working length effortlessly and of bringing a high volume of irrigant close to the apex. The product has been shown to be effective in curved canals, but what about challenging cases? The following case reports demonstrate the use of IrriFlex in two different scenarios: a retreatment and a primary treatment of a calcied canal.

Case 1

A 62-year-old patient was referred to our clinic for endodontic retreatment. The patient reported swelling of the maxillary left gingiva. The radiographic examination revealed the results of a previous endodontic therapy and the presence of periapical radiolucencies (Fig. 1).

Since the results of the previous therapy could be improved, we decided to retreat the tooth, passing through the existing crown.
After positioning of the dental dam (Fig. 2), the existing composite lling in the centre of the crown was removed using a diamond-coated bur driven by a high-speed handpiece. In this way, the access cavity was created and rened in order to see the pulp chamber (Fig. 3). The existing root canal lling was removed using rotary instruments specically designed for retreatment, and then ultrasonic tips were used to remove the remnants on the pulp chamber oor. The chamber was lled with 5% sodium hypochlorite (Fig. 4), and the second mesiobuccal canal, which had not been shaped, cleaned or filled during the initial treatment, was located and shaped according to the standard protocol.

Considering the presence of an endodontic lesion and swelling, a great deal of time was dedicated to decontamination of the root canal system (Fig. 5).The device chosen to deliver the irrigating solution to the working length was IrriFlex (Figs. 6 & 7) because, thanks to its exibility, it would be able to deliver the irrigant to the apical third of each root, without any effort, without stopping in case of curvatures. The irrigant was then activated by means of ultrasonic inserts according to the indications given by Tonini and Cerutti.

After ensuring that the root canals were dry, they were filled according to the warm gutta-percha compaction technique (Figs. 8–10). After that, the access cavity was filled by means of a direct composite restoration (Fig. 11) and a postoperative radiograph was taken in order to check the nal result (Fig. 12).

Case 2

A 50-year-old patient came to our ofce because of an emergency: while eating, he had broken tooth #22
and he was not able to nd the fragment (Fig. 13). The fracture had exposed the pulp and the patient reported spontaneous and acute pain. The preoperative radiograph showed that the tooth had a very thin canal lumen (Fig. 14) and sufcient bone support.

It was thus decided to do an endodontic treatment followed by restoration with a prosthetic crown. As a first step of the therapy, a dental dam was positioned directly around the remaining tooth structure and the root canal therapy was started. The access cavity was created, and the root canal opening was located and enlarged using ultrasonic tips. Then nickel–titanium rotary instruments were used to complete the shaping of this narrow root canal space (Fig. 15). Multiple irrigation sequences were repeated using IrriFlex and ultrasonic activation of the sodium hypochlorite, both in order to have the endodontic instruments work in the presence of an irrigating solution and to decrease the bacterial load. The great advantage of using a polypropylene irrigation cannula was that, once the last shaping instrument had reached the working length, the cannula reached the working length smoothly too (Figs. 16 & 17), allowing the dentist to bring the irrigant as close as possible to the apical constriction.

When the root canal walls looked sufficiently clean and shiny, obturation with warm gutta-percha was performed. As a last step of the endodontic treatment, a build-up was done with composite (Fig. 18) and a periapical radiograph was taken (Fig. 19).

Conclusion

The same experienced practitioner performed the two root canal therapies reported in this article. The cases were extremely different, an initial treatment of a single-rooted tooth and a retreatment of a multi-rooted tooth, but both of them were challenging. The instruments and the sequences used for shaping the root canal system differed between the cases, since the root canal taper was different and the apical size of the lateral incisor was discernibly smaller than that of the molar.
The thing that did not change in the approach to these cases was the attention paid to the irrigation step. In the retreatment, the eradication of bacteria was the key to success in a tooth that had already received an endodontic treatment that had failed, whereas in the lateral incisor, the presence of a narrow canal made it more difficult to clean the complexity of the root canal system.
In both cases, the use of a flexible irrigation cannula that follows the path created by the endodontic instruments precisely made the treatment easier and reduced operating times, because it was possible to deliver a large volume of irrigating solution where it was needed the most. The presence of length marks on the cannula helped the clinician establish the needle penetration inside the root canal; the yellow stop was put on the cannula to emphasise the correspondence between working length and IrriFlex depth of penetration inside the prepared canal. Obturation with warm gutta-percha was performed in order to seal the root canal space in 3D, and the choice to restore both teeth in the same appointment as that of the root canal therapy was meant to prevent coronal leakage often associated with provisional restorations.

Dr Marco Martignoni, Italy