Assessment of Smear Layer Removal and Penetration Depth of Root Canal Irrigant Using Different Irrigation Activation Systems: A Comparative Study

INTRODUCTION

The goal of an endodontic treatment is to eradicate microorganisms from affected radicular canals by combining a biomechanical technique with an antibacterial therapy to induce periapical tissue repair. The purpose of instrumentation in clinical practice is to remove a portion of hard tissue from the root canal, make it easier for irrigants to reach the apical anatomy, and shape the canal system so that a permanent root filling can be placed in it. It is not possible to reliably eradicate the bacteria from infected root canals using mechanical instrumentation or saline irrigation alone; nevertheless, enough irrigation in conjunction with instrumentation is necessary to finish the cleaning process and lower the microbial load in the canal system.¹

The irrigants must reach the working length (WL) through an efficient irrigation delivery system. To effectively debride the entire canal system, such a delivery system must have sufficient flow and deliver a sufficient volume of irrigant all the way to WL. There have been reports that the smear layer and debris from the intricate anatomy of the root canal system could not be removed by hand irrigation.²

The traditional needle irrigation method is the one that is most frequently utilized. It entails changing and restocking the irrigant in the canal’s apical third.³ Since this irrigating technique’s effectiveness is not all that great, better cleaning especially in complex areas requires improved procedures. Over time, a number of additional methods have emerged, including ultrasonically activated irrigation and hand dynamic agitation of gutta percha cones.⁴ Recently, an EndoVac system was showcased and it is one among the irrigation systems which creates a negative apical pressure. The objective of this system is to deliver an effective and safe canal cleaning, particularly in the apical portion of the root canal. Passive ultrasonic irrigation (PUI) relies on the transmission of acoustic energy from an oscillating file or smooth wire to an irrigant in the root canal.⁵ An irrigation file is positioned in the center of the root canal, as far as the apical region, after the root canal has been shaped to the master apical file. Next, the irrigant is activated by stimulating the irrigation file to oscillate ultrasonically.⁶ There is a dearth of information on the comparison between PUI devices and conventional needles with EndoVac. Hence, the present study was conducted to evaluate the penetration depth and smear layer removal of root canal irrigant using three various irrigation activation techniques.

MATERIALS AND METHODS

RESULTS

Table 1 presents the mean smear layer removal efficacy of three different irrigation activation systems at coronal third. The maximum smear layer was removed using activation of EndoVac system group (1.26 ± 0.02), followed by PUI group (1.84 ± 0.16) and irrigation with conventional needle group (2.89 ± 0.21). There was a highly significant difference found between the three different irrigation systems.

Table 2 depicts the mean smear layer removal efficacy of three different irrigation activation systems at the middle third. The more smear layer was removed using activation of EndoVac system group (1.18 ± 0.10), followed by PUI group (1.72 ± 0.09) and irrigation with conventional needle group (2.66 ± 0.18). There was a highly significant difference found between the three different irrigation systems (p < 0.001).

Table 3 presented the mean smear layer removal efficacy of three different irrigation activation systems at the apical third. The more smear layer was removed using activation of EndoVac system group (1.02 ± 0.01) followed by PUI group (1.58 ± 0.08) and irrigation with conventional needle group (2.38 ± 0.06). A highly significant difference was observed between the three different irrigation systems (p < 0.001).

The inference of the present study includes that the maximum smear layer removed in EndoVac system group was compared with the PUI and conventional needle group.

DISCUSSION

Debridement of the root canal system is crucial to the success of endodontics. Smear layers are created by biomechanical preparation processes and consist of both inorganic and organic particles. Cleaning results from irrigation are superior to those from root canal preparation alone. It eliminates the smear layer, flushes out trash, and destroys bacteria. Treatment outcome could be affected if the smear layer is not removed during the final irrigation.⁸

The most effective irrigant solution currently available for removing the smear layer is EDTA; in the current investigation, a final rinse using 17% EDTA, and then 5.25% NaOCl was utilized following instrumentation since it consistently removed debris. Regarding the ideal volume or activation technique for the irrigating solutions, there is, nevertheless, disagreement.⁹

Even though there have been a lot of new endodontic instruments developed in the past 10 years, research indicates that at least 10% of the primary root canal walls are still unaffected by the instruments, and that the number rises to over 50% in cases where the root canal has anatomic abnormalities that include isthmuses and recesses.¹⁰ Research carried out by Lacerda MFLS et al.¹¹ and Zuolo ML et al.¹² revealed that even in straight root canals, over 10% of the dentine walls remained unaltered by tools that claimed to mechanically clean the root canal in three dimensions. Thus, cleaning untreated walls and places inaccessible to mechanical equipment requires efficient irrigation.

According to the current study’s findings, the EndoVac system statistically removes more debris (p < 0.05) than the conventional irrigation in the middle and coronal sections of the samples in addition to the apical third of the root canal. The EndoVac system’s creation of a negative apical pressure may be the cause of these clean canal outcomes. The irrigant is drawn down the canal walls up to the apex by the negative apical pressure, creating a swift turbulent current force that travels toward the microcannula’s termination. The debris is removed from the closed apical end of the root canals via the microcannula’s orifices. The results of the present study were in agreement with Siu C and Baumgartner JC¹³ and Nielsen BA and Baumgartner JC¹⁴ who concluded that the EndoVac system is more effective than the conventional irrigation in the removal of debris at 1 mm from the WL (p < 0.05). At every 6 seconds, the microcannula in the current investigation was pushed 2 mm up from the WL to the coronal section. The microcannula was positioned at the WL after the timer went off, because this apical-coronal motion persisted for 30 seconds.

The current investigation found that the efficacy of PUI in removing smear layers was superior to that of conventional needle irrigation. Shear stress pressures are created adjacent to the canal walls by the oscillation of the instrument, and PUI activates the irrigant by producing acoustic microstreaming. The findings are consistent with the research done by Walmsley AD and Williams AR¹⁵ and Blank-Gonçalves LM et al.,¹⁶ which revealed that for ultrasonic irrigation to have the greatest impact, the passive file must be able to oscillate freely inside the canal without coming into touch with the walls. According to research done by Jiang LM et al.,¹⁷ cleaning effectiveness rises in step with ultrasonic activation power. They discovered that the group with the greatest output had the best cleaning outcomes. In the current investigation, all three levels of the smear layer were successfully removed using low level ultrasonic irrigation.

The conventional irrigation is still used by both endodontists and general practitioners. It comprises either passively or actively agitating the irrigant while inserting needles of various gauges into the canal. The needle in the canal moves up and down to agitate the tissue. Certain needles are made to deliver the irrigant through the distal end, while others have a closed-ended side vent that allows the irrigant to be supplied laterally. The irrigant is delivered by the conventional needle irrigation approach no more than 0–1.1 mm beyond the needle tip. The intricate anatomical regions (such as the lateral canals, isthmuses, fins, and accessory canals) are not sufficiently cleaned by method.¹⁸

The present study’s limitations include the fact that it was conducted in vitro and that a complete replication of the intraoral environment was not possible. Long-term clinical investigations are therefore advised to validate the findings of this investigation.

CONCLUSION

Within limitation, the present study concluded that every irrigation device that was evaluated was successful in removing the smear layer from the root canal. However, EndoVac system group removed a greater amount of smear layer compared to PUI and conventional needle group. The success of endodontic treatment mainly depends on the removal of bacteria, dentin debris, and necrotic and inflammatory pulp tissue.

REFERENCES

1. Estrela C, Estrela CR, Decurcio DA, et al. Anti-microbial efficacy of ozonated water, gaseous ozone, sodium hypochlorite and chlorhexidine in infected human root canals. Int Endod J 2007;40:85–93. DOI: 10.1111/j.1365-2591.2006.01185.x.

2. Paque F, Al-Jadaa A, Kafir A. Hard-tissue debris accumulation created by conventional rotary versus self-adjusting file instrumentation of mandibular molars in mesial root canal systems. Int Endod J 2012;45(5):413–418. DOI: 10.1111/j.1365-2591.2011.01991.x.

3. Gade VJ, Sedani SK, Lokade JS, et al. Comparative evaluation of debris removal from root canal wall by using EndoVac and conventional needle irrigation: An in vitro study. Contemp Clin Dent 2013;4:432–436. DOI: 10.4103/0976-237X.123019.

4. Ahmetoglu F, Keles A, Yalcin M, et al. Effectiveness of different irrigation systems on smear layer removal: A scanning electron microscopic study. Eur J Dent 2014;8(1):53–57. DOI: 10.4103/1305-7456.126241.

5. Saber Sel D, Hashem AA. Efficacy of different final irrigation activation techniques on smear layer removal. J Endod 2011;37:1272–1275. DOI: 10.1016/j.joen.2011.06.007.

6. Krell KV, Johnson RJ, Madison S. Irrigation patterns during ultrasonic canal instrumentation. Part I. K-type files. J Endod 1988;14:65–68. DOI: 10.1016/S0099-2399(88)80003-7.

7. Torabinejad M, Khademi AA, Babagoli J, et al. A new solution for the removal of the smear layer. J Endod 2003;29(3):170–175. DOI: 10.1097/00004770-200303000-00002.

8. Birajdar A, Sathe S, Dixit M, et al. Comparative evaluation of the efficacy of three different irrigation devices in removal of debris from isthmus: An in vitro study. Endodontology 2016;28:2–6. DOI: 10.4103/0970-7212.184318.

9. Carvalho AS, Camargo CHR, Valera MC, et al. Smear layer removal by auxiliary chemical substances in biomechanical preparation: A scanning electron microscope study. J Endod 2008;34:1936–1400. DOI: 10.1016/j.joen.2008.08.012.

10. Siqueira JF Jr, Pérez AR, Marceliano-Alves MF, et al. What happens to unprepared root canal walls: A correlative analysis using micro-computed tomography and histology/scanning electron microscopy. Int Endod J 2018;51(5):501–508. DOI: 10.1111/iej.12753.

11. Lacerda MFLS, Marceliano-Alves MF, Pérez AR, et al. Cleaning and shaping oval canals with 3 instrumentation systems: A correlative micro-computed tomographic and histologic study. J Endod 2017;43(11):1878–1884. DOI: 10.1016/j.joen.2017.06.032.

12. Zuolo ML, Zaia AA, Belladonna FG, et al. Micro-CT assessment of the shaping ability of four root canal instrumentation systems in oval-shaped canals. Int Endod J 2018;51(5): 564–571. DOI: 10.1111/iej.12810.

13. Siu C, Baumgartner JC. Comparison of the debridement efficacy of the EndoVac irrigation system and conventional needle root canal irrigation in vivo. J Endod 2010;36:1782–1785. DOI: 10.1016/j.joen.2010.08.023.

14. Nielsen BA, Baumgartner JC. Comparison of the EndoVac system to needle irrigation of root canals. J Endod 2007;33:611–615. DOI: 10.1016/j.joen.2007.01.020.

15. Walmsley AD, Williams AR. Effects of constraint on the oscillatory pattern of endosonic files. J Endod 1989;15:189–194. DOI: 10.1016/S0099-2399(89)80233-X.

16. Blank-Gonçalves LM, Nabeshima CK, Martins GH, et al. Qualitative analysis of the removal of the smear layer in the apical third of curved roots: Conventional irrigation versus activation systems. J Endod 2011;37:1268–1271. DOI: 10.1016/j.joen.2011.06.009.

17. Jiang LM, Verhaagen B, Versluis M, et al. The influence of the ultrasonic intensity on the cleaning efficacy of passive ultrasonic irrigation. J Endod 2011;37:688–692. DOI: 10.1016/j.joen.2011.02.004.

18. Gu LS, Kim JR, Ling J, et al. Review of contemporary irrigant agitation techniques and devices. J Endod 2009;35:791–804. DOI: 10.1016/j.joen.2009.03.010.