best and although MDA may be perceived by some clinicians as laborious, it is a fast, costeffective, safe, and convenient method to perform irrigant agitation at the end of the root canal preparation.

References

1. Andrabi SM, Kumar A, Mishra SK, Tewari RK, Alam S, Siddiqui S. Effect of manual dynamic activation on smear layer removal efficacy of ethylenediaminetetraacetic acid and SmearClear: an in vitro scanning electron microscopic study. Aust Endod

J. 2013;39:131–6.

2.Baumgartner JC, Cuenin PR. Efficacy of several concentrations of sodium hypochlorite for root canal irrigation. J Endod. 1992;18:605–12.

3. Boutsioukis C, Psimma Z, Kastrinakis E. The effect of flow rate and agitation technique on irrigant extrusion ex vivo. Int Endod J. 2014;47:487–96. doi:10.1111/ iej.12176.

4. Boutsioukis C, Psimma Z, van der Sluis LW. Factors affecting irrigant extrusion during root canal irrigation: a systematic review. Int Endod J. 2013;46(5):99–618.

LW. Formation and removal of apical vapor lock during syringe irrigation: a combined experimental and Computational Fluid Dynamics approach. Int Endod

J. 2014;47:191–201.

6.Bronnec F, Bouillaguet S, Machtou P. Ex vivo assessment of irrigant penetration and renewal during the final irrigation regimen. Int Endod J. 2010;43:663–72.

7.Byström A, Sundqvist G. Bacteriologic evaluation of the effect of 0.5 percent sodium hypochlorite in endodontic therapy. Oral Surg Oral Med Oral Pathol. 1983;55:307–12.

8. Capar ID, Aydinbelge HA. Surface change of root canal dentin after the use of irrigation activation protocols: electron microscopy and an energy-dispersive X-ray microanalysis. Microsc Res Tech. 2013;76:893–6.

9. Caron G, Nham K, Bronnec F, Machtou P. Effectiveness of different final irrigant activation

protocols on smear layer removal in curved canals. J Endod. 2010;36:1361–6.

10. Dai L, Khechen K, Khan S, Gillen B, Loushine BA, Wimmer CE, Gutmann JL, Pashley D, Tay FR. The effect of QMix, an experimental antibacterial root canal irrigant, on removal of canal wall smear layer and debris. J Endod. 2011;37:80–4.

11. de Gregorio C, Estevez R, Cisneros R, Heilborn C, Cohenca N. Effect of EDTA, sonic, and ultrasonic activation on the penetration of sodium hypochlorite into simulated lateral canals: an in vitro study. J Endod. 2009;35:891–5.

12.Deleu E, Meire MA, De Moor RJ. Efficacy of laserbased irrigant activation methods in removing debris from simulated root canal irregularities. Lasers Med Sci. 2015;30:831–5.

13. Desai P, Himel V. Comparative safety of various intracanal irrigation systems. J Endod. 2009;35:545–9.

14.Druttman AC, Stock CJ. An in vitro comparison of ultrasonic and conventional methods of irrigant replacement. Int Endod J. 1989;22:174–8.

15.Dutner J, Mines P, Anderson A. Irrigation trends among American Association of Endodontists mem-

bers: a web-based survey. J Endod. 2012;38:37–40. 16. Gao Y, Haapasalo M, Shen Y, Wu H, Li B, Ruse

ND, Zhou X. Development and validation of a threedimensional computational fluid dynamics model of root canal irrigation. J Endod. 2009;35:1282–7.

17. Goode N, Khan S, Eid AA, Niu LN, Gosier J, Susin LF, Pashley DH, Tay FR. Wall shear stress effects of different endodontic irrigation techniques and systems. J Dent. 2013;41:636–41.

18. Gu LS, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of contemporary irrigant agitation techniques and devices. J Endod. 2009;35:791–804.

19. Gulabivala K, Ng YL, Gilbertson M, Eames I. The fluid mechanics of root canal irrigation. Physiol Meas. 2010;31:R49–84.

20.Huang TY, Gulabivala K, Ng YL. A bio-molecular film ex-vivo model to evaluate the influence of canal dimensions and irrigation variables on the efficacy of irrigation. Int Endod J. 2008;41:60–71.

21.Jiang LM, Lak B, Eijsvogels LM, Wesselink P, van der Sluis LW. Comparison of the cleaning efficacy of different final irrigation techniques. J Endod. 2012;38:838–41.

22.Luks S. Practical endodontics. Philadelphia: JB Lippincott; 1974. p. 82–5.

23.Machtou P. Investigations sur l’irrigation en endodon-

tie. Thèse de doctorat en sciences odontologiques, Université Paris 7, Paris; 1980.

24. McGill S, Gulabivala K, Mordan N, Ng YL. The efficacy of dynamic irrigation using a commercially available system (RinsEndo) determined by removal of a collagen ‘bio-molecular film’ from an ex vivo model. Int Endod J. 2008;41:602–8.

25.Molven O, Olsen I, Kerekes K. Scanning electron microscopy of bacteria in the apical part of root canals in permanent teeth with periapical lesions. Endod Dent Traumatol. 1991;7:226–9.

26.Moorer WR, Wesselink PR. Factors promoting the tissue dissolving capability of sodium hypochlorite. Int Endod J. 1982;15:187–96.

27.Nair PNR. Pathogenesis of apical periodontitis and the causes of endodontic failures. Crit Rev Oral Biol Med. 2004;15:348–81.

28. Parente JM, Loushine RJ, Susin L, Gu L, Looney SW, Weller RN, Pashley DH, Tay FR. Root canal debridement using manual dynamic agitation or the EndoVac for final irrigation in a closed system and an open system. Int Endod J. 2010;43:1001–12.

29.Ribeiro EM, Silva-Sousa YT, Souza-Gabriel AE, Sousa-Neto MD, Lorencetti KT, Silva SR. Debris and smear removal in flattened root canals after use of different irrigant agitation protocols. Microsc Res Tech. 2012;75:781–90.

30.Saber Sel D, Hashem AA. Efficacy of different final irrigation activation techniques on smear layer removal. J Endod. 2011;37:1272–5.

31.Schoeffel GJ. The EndoVac method of endodontic irrigation: safety first. Dent Today. 2007;26:92, 94, 96.

32. Senia ES, Marshall JF, Rosen S. The solvent action of sodium hypochlorite on pulp tissue of extracted teeth. Oral Surg Oral Med Oral Pathol. 1971;31:96–103.

33.Siqueira Jr JF, Rôças IN. Clinical implications and microbiology of bacterial persistence after treatment procedures. J Endod. 2008;34:1291–301.

34. Stojicic S, Shen Y, Qian W, Johnson B, Haapasalo M. Antibacterial and smear layer removal ability of a novel irrigant, QMiX. Int Endod J. 2012;45:363–71.

35. Susin L, Liu Y, Yoon JC, Parente JM, Loushine RJ, Ricucci D, Bryan T, Weller RN, Pashley DH, Tay FR. Canal and isthmus debridement efficacies of two irrigant agitation techniques in a closed system. Int Endod J. 2010;43:1077–90.

36. Tay FR, Gu LS, Schoeffel GJ, Wimmer C, Susin L, Zhang K, et al. Effect of vapor lock on root canal debridement by using a side-vented needle for positive-pressure irrigant delivery. J Endod. 2010; 36:745–50.

37. The SD. The solvent action of sodium hypochlorite on fixed and unfixed necrotic tissue. Oral Surg Oral Med Oral Pathol. 1979;47:558–61.

38.Trepagnier CM, Madden RM, Lazzari EP. Quantitative study of sodium hypochlorite as an in vitro endodontic irrigant. J Endod. 1977;3:194–6.

39.Vera J, Hernández EM, Romero M, Arias A, van der Sluis LW. Effect of maintaining apical patency on irrigant penetration into the apical two millimeters of large root canals: an in vivo study. J Endod. 2012;38:1340–3.

40.Vivan RR, Bortolo MV, Duarte MA, Moraes IG, Tanomaru-Filho M, Bramante CM. Scanning electron microscopy analysis of RinsEndo system and conventional irrigation for debris removal. Braz Dent J. 2010;21:305–9.

41.Yana Y. An in vivo comparative study of the penetration of sodium hypochlorite in root canal systems during cleaning and shaping procedures using the B.U. technique and sonic instrumentation. Masters thesis, Boston University, Boston; 1989.

42.Zehnder M. Root canal irrigants. J Endod. 2006;32: 389–98.

The Challenge of Endodontic

Debridement

Adequate debridement of the apical one third of the root canal can be very challenging and must not be discounted from providing high-quality endodontic care. Successful endodontic treatment depends on a number of factors, including proper instrumentation, successful irrigation and decontamination of the root canal system to the apices and in areas such as isthmuses and lateral and accessory canals [1]. After traditional nickelÐ titanium instrumentation and syringe-assisted irrigation, inaccessible areas such as isthmuses, Þns, accessory canals and the root canal terminus may remain Þlled with residual debris and microorganisms [2, 3]. The presence of persistent microbes and their by-products could result in persistent periradicular inßammation [4]. Delivering an endodontic irrigant with a needle and a syringe may be unpredictable, thereby not allowing the irrigant to reach root canal anastomoses and the apical one third of the principal canals. Unless the needle of a positive-pressure delivery system is placed close to the apex, the portion of the canal from the apex to the end of the needle may not be reached by the irrigant [5]. When the needle is placed to a depth that allows the irrigation solution to reach the apex, it is possible the solution may enter the periapical tissues [6]. This can be a source of post-operative pain, and if a signiÞcant quantity of a toxic irrigant such as NaOCl is injected into the periapical tissue, the potential to experience a NaOCl accident increases [7]. With debris and bacteria frequently surviving the cleaning and shaping procedures, adjuvant techniques, to the traditional syringe and needle commonly used, may result in superior root canal cleaning [3, 8].

agitation using a gutta-percha point. Machineassisted irrigation techniques include sonics and ultrasonics, as well as newer systems such as the EndoVac, based on apical negative pressure (SybronEndo); the GentleWave (Sonendo), based on multisonic pressure wave formation; the plastic rotary F File (Plastic Endo); the Vibringe (Vibringe); the Rinsendo (Air Techniques); and the EndoActivator (Dentsply Tulsa Dental Specialties). Two important factors that should be considered during the process of irrigation are whether the irrigation systems can deliver the irrigant to the apical terminus and whether the irrigant is capable of debriding areas that could not be reached with mechanical instrumentation, such as lateral/accessory canals, isthmuses and deltas.

Continuous and Intermittent

Flushing Techniques

Two ßushing methods are currently employed to irrigate root canal systems: the continuous and intermittent. With the intermittent ßush technique, the irrigant is injected in the root canal space with a syringe and the irrigant solution can then be activated; the canal is Þlled several times after each activation cycle. Inversely, the continuous ßush techniques provide an uninterrupted supply of fresh irrigation solution into the root canal. This technique can provide more effective results and reduce the time required for Þnal irrigation when compared with intermittent irrigation devices. Taking into consideration that chloride (responsible for dissolving the organic tissues and NaOClÕs antibacterial property) is unstable and quickly consumed, a continuous ßow of irrigant would make intuitive sense.

Manual and Machine-Assisted

Irrigation Techniques

Root canal irrigation systems can be divided into two categories: manual irrigation techniques and machine-assisted irrigation techniques [9]. Manual irrigation techniques include the positive-pressure syringe Þtted with a variety of needle designs and the manual-dynamic

Apical Negative Pressure

Pressure is deÞned as a force per unit area. During root canal treatment, pressure is exerted against the root canal wall when the irrigant solution is delivered into the root canal space. Negative pressure refers to a situation in which an enclosed volume has lower pressure than its surroundings.