A2 ENDO TRIBUNE Dental Tribune Middle East & Africa Edition | 5/2020 Clinical aspects of endodontic disinfection By Drs. Riccardo Tonini & Francesca Cerutti, Italy is present) and preventing reinfec- tion16. Root canal systems can often show complex anatomies, with great vari- ations in number and shape, as re- cently summarized by Versiani and Ordinola-Zapata, which described almost all anatomical confi gurations possible to be observed in a single root.1 Anatomic factors may pose a sig- nifi cantly challenge to root canal shaping. Curvatures, oval/fl attened canals and other pathologic or iat- rogenic conditions may infl uence attainment of a proper continuous conical shape during instrumenta- tion. Different preparation tech- niques leave 10 to 50% of the root canal surface area untouched.2,3 Moreover, several studies have dem- onstrated the impossibility to obtain a complete mechanical debridement or chemical disinfection of the isth- muses and accessory or lateral canals with the current technology, mostly because, in canals with irregular cross section, the instrument may not reach all recesses, thus hard tis- sue debris remain packed into these areas during the mechanical prepa- ration of the root canal system.4-6 The main reasons for bacteria to persist after chemomechanical pro- cedures are that they are resistant to treatment or they are unaffected by instruments/irrigants. While some microorganisms have been shown to be resistant to some endodontic antimicrobial agents7,8, resistance to debridement and to NaOCl is highly unlikely to occur9. Anatomic complexities represent a challenge to adequate disinfection, since, in general, the main canal lu- men and minor irregularities are in- corporated into the preparation and affected by NaOCl, but bacteria and organic tissue may remain in areas not reached by instruments and ir- rigants. Bacteria can spread through these pathways, reaching the peri- odontal ligament and causing dis- ease10, especially in the apical area, where accessory canals are likely to be present, according to De Deus and Vertucci11,12. These areas are usually not affected because of the limita- tions of instruments and the short retention time of irrigants within the root canal1. From the clinical point of view, the infection of the above mentioned complex anatomical confi gurations, with several portals of exit, can be the cause of failure of primary and secondary non-surgical endodontic treatments; for this reason, an ad- equate infection control is necessary not only in the main canal lumen, but also in the entire root canal sys- tem6. Shaping does an important part in the endodontic treatment, but irri- gants are in charge of the decontami- nation of the areas that cannot be reached by the fi les2,13,14. Bringing the irrigating solution as close as possi- ble to the apex and ensuring a good irrigant exchange, together with ac- tivating it, is extremely important to reach the success in endodontic retreatments15,16 treatments and (Figs. 1-4). Irrigation is the step that is aimed to remove as many bacteria as possible from the root canal space, promot- ing apical healing (in case a lesion Some clinical aspects of endodontic disinfection can be critical, as the scarce penetration of the irrigating solution and the irrigant exchange in complex anatomies, together with the biofi lm resistance to the action of the irrigants17. Clinical and in vitro studies have demonstrated that the combina- tion of mechanical preparation and antibacterial irrigants signifi cantly enhances disinfection when com- pared to irrigation with saline18. The main requirement is to exchange frequently the irrigating solutions and use suffi cient volumes in order to maintain the antibacterial ef- fectiveness of the NaOCl solution, compensating for the effects of con- centration1. One simple method to improve the irrigant exchange and to activate the solution is the push-pull technique. Most clinician consider irrigation as the extrusion of an irrigant from a syringe gripped by holding the in- dex and middle fi ngers under the wings of the syringe and the thumb over the plunger. A simple yet effec- tive method to improve the cleanli- ness of the root canal system, that does not require the use of special devices, consists in alternating posi- tive and negative irrigation using the push pull technique. After extruding a small amount of irrigant, the cli- nician places the thumb under the plunger and pushes upwards, devel- oping a negative pressure that op- poses the pressure used to inject the irrigant into the canal: this causes a suction of fl uids into the canals, im- proving the fl uid dynamics within the root canal system. In this way, keeping the needle sta- tionary and moving the plunger, the liquids have a better penetration into the canals, acting more effectively (as the buffer effect is decreased by a constant exchange of solutions)1920. During the negative pressure phase, the fl uids in the canal return to the syringe by capillarity and are reac- tivated, while any pathogens are eliminated thanks to the action of the irrigant solution (Figs. 5-7). This creates an ideal condition for the next active irrigation phase, be- cause the new irrigant can come into contact with the entire dentine sur- face (Fig. 8). This simple technique is also able to reveal to the operator any confl u- ence of apparently independent ca- nals: in this case it will be suffi cient to observe if, during the suction phase carried out in one canal, the irrigant disappears from the adjacent canal. The clinician, during the execution of the technique, should try not to introduce air into the root canal16 (Figs. 9,10). One signifi cant improvement to this technique is represented by the introduction in the market of a poly- propylene irrigation needle devel- oped by Produits Dentaires (Switzer- land) and named IrriFlex. Thanks to an innovative back-to- back side vent design that improves the fl uid dynamics into the canal, Ir- riFlex allows performing a safe and effi cient cleaning of the root canal system, even in presence of challeng- ing diffi cult anatomies. Fig. 1: A large decay on tooth 4.5 makes it necessary to plan an endodontic treatment. The anatomy of the tooth is similar to that described by Versiani et al. Fig. 5: The bitewing X-ray shows an extensive hard tissue loss on the tooth 3.6. Fig. 2: The access cavity is designed after removing the decayed tissue. Two thin root canals have been shaped and cleaned, then a fi nal irrigation is performed using the push-pull technique. The presence of notches on the shank of the irrigation cannula makes it easier to control the correspondence between the working length and the position of the cannula into the canal. Fig. 6: The push-pull technique is used while irrigation with IrriFlex. Fig. 3: The postoperative X-ray confi rms the presence of an articulated anatomy that was treated thanks to the synergic use of shaping instruments and sodium hypochlorite, brought into the root canal system by means of IrriFlex, a polypropylene irrigation needle by Produits Dentaires. The tooth is restored with and indirect composite overlay. Fig. 7: The postoperative X-ray shows the correct fi lling of the root canal system. 4a 4b Fig. 8: Detail of the irrigant fl ow in the apical area. Fig. 9: The patient refers spontaneous pain to the tooth 2.6. Fig. 4a,b: The tooth 3.4 presents a large decay and requires en- dodontic treatment. The postoperative X-ray shows the presence of a loop in the root canal system. Several articles described the superior adaptation of Ir- riFlex in curved canals, thanks to its 30G tip and supe- rior fl exibility with respect to steel or Ni-Ti, following the anatomy of the root until the working length, without the risk of blocking. The possibility to bring the irrigant where it is most needed and to deliver a large volume of solution with no effort, together with the possibility for the operator to control the depth at which the tip is (thanks to the mil- limetric notches printed on the shank of the cannula), helps improving the disinfection step of the root canal treatment, making it more ergonomic and safer. IrriFlex improves fl uid dynamics throughout the root canal system, retaining the safety features of closed tip needles: the irrigant, in fact, can only fl ow coronally and the two microscopic outlets induce atomization of the liquid, effective fl uid dynamics turbulence for fl uid re- placement and improve the removal of dentine debris. It Fig. 10: The postoperative X-ray shows the presence of multiple lateral canals. also works perfectly with the push-pull technique, allow- ing an increased irrigant exchange in the apical third of the root. The introduction of technological innovations in en- dodontics helps achieving more easily repeatable and predictable results, with benefi ts for the patient and the operator.