The investigation of endodontic irrigants and polyhexanide-based solution action on smear layer

AIM. The effect of irrigants on the smear layer on the intracanalicular dentin surface is one of the important issues in endodontics. The objective of this article is to determine the effect of different concentrations of polyhexanide-based solutions and standard irrigants on the smear layer using scanning electron microscopy (SEM).
MATERIALS AND METHODS. The present study was conducted on 42 extracted teeth (third molars, first and second premolars) with formed apices that had been extracted for orthodontic indications. The teeth were decoronated and samples were prepared. In order to create a smear layer, the lumen of the canals was instrumented with H-file #40 throughout. A simulation of root canal irrigation was conducted by immersing the specimens in a 5-ml container filled with the proper solution for 1 hour: group 1 – no treatment (n = 6); group 2 – saline (n = 6); group 3 – 2% chlorhexidine (n = 6); group 4 – 3% sodium hypochlorite (n = 6); group 5 – 17% EDTA; group 6 – polyhexanide 0.1% (n = 6); group 7 – polyhexanide 0.2% (n = 6). A ~30 nm thick platinum film was sputtered onto the surface of each sample using a magnetron deposition technique. SEM microphotos were acquired on a Vega3 TESCAN scanning electron microscope (SEM) with an SE secondary electron detector, which enables imaging with high topographic contrast. The initial detector (incamera) was employed for image acquisition, with an electron energy of 30 keV. Images were acquired at magnifications of x20 (overview image), x150, x250, x500, x1000, x2500, x7500 for each sample.
RESULTS. The samples from groups 1 and 5 demonstrated the absence of a smear layer on the dentin surface and the absence of smear plugs in the dentinal tubules. Groups 2 and 3 are distinguished by the deposition of a pronounced amorphous smear layer and the obturation of all dentinal tubules. Groups 4, 6, and 7 are distinguished by the deposition of a smaller volume of smear layer on the dentin surface, as well as the presence of semi-open or completely open entrances to the dentinal tubules.
CONCLUSION. The data obtained indicates that antiseptic compositions based on polyhexanide in concentrations of 0.1 and 0.2% do not have a pronounced effect on the smear layer. However, in visual evaluation of SEM micrographs, their effect is comparable to that of 3% sodium hypochlorite. In instances where enhanced dissolution of the smear layer and smear plugs from the tubules is necessary to facilitate decontamination of the wall dentin, the combination of antiseptics with chelate compounds, such as 17% EDTA, may be employed.

1. Siqueira J.F. Jr, Rôças I.N. Clinical implications and microbiology of bacterial persistence after treatment procedures. J Endod. 2008;34(11):1291–1301.e3. https://orcid.org/10.1016/j.joen.2008.07.028

2. Zehnder M. Root canal irrigants. J Endod. 2006;32(5): 389–398. https://orcid.org/10.1016/j.joen.2005.09.014

3. Haapasalo M., Shen Y., Qian W., Gao Y. Irrigation in endodontics. Dent Clin North Am. 2010;54(2):291–312. https://orcid.org/10.1016/j.cden.2009.12.001

4. Tirali R.E., Bodur H., Ece G. In vitro antimicrobial activity of sodium hypochlorite, chlorhexidine gluconate and octenidine dihydrochloride in elimination of microorganisms within dentinal tubules of primary and permanent teeth. Med Oral Patol Oral Cir Bucal. 2012;17(3):e517–522. https://orcid.org/10.4317/medoral.17566

5. Arias-Moliz M.T., Ferrer-Luque C.M., Espigares-Rodríguez E., Liébana-Ureña J., Espigares-García M. Bactericidal activity of phosphoric acid, citric acid, and EDTA solutions against Enterococcus faecalis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2008;106(2):e84–89. https://orcid.org/10.1016/j.tripleo.2008.04.002

6. Violich D.R., Chandler N.P. The smear layer in endodontics – a review. Int Endod J. 2010;43(1):2–15. https://orcid.org/10.1111/j.1365-2591.2009.01627.x

7. Drews D.J., Nguyen A.D., Diederich A., Gernhardt C.R. The interaction of two widely used endodontic irrigants, chlorhexidine and sodium hypochlorite, and its impact on the disinfection protocol during root canal treatment. Antibiotics. 2023;12(3):589. https://orcid.org/10.3390/antibiotics12030589

8. Bilvinaite G., Zongolaviciute R., Drukteinis S., Bukelskiene V., Cotti E. Cytotoxicity and efficacy in debris and smear layer removal of HOCl-based irrigating solution: An in vitro study. J Funct Biomater. 2022;13(3):95. https://doi.org/10.3390/jfb13030095

9. Garberoglio R., Becce C. Smear layer removal by root canal irrigants. A comparative scanning electron microscopic study. Oral Surg Oral Med Oral Pathol. 1994;78(3):359–367. https://doi.org/10.1016/0030-4220(94)90069-8

10. Teixeira C.S., Felippe M.C., Felippe W.T. The effect of application time of EDTA and NaOCl on intracanal smear layer removal: an SEM analysis. Int Endod J. 2005;38(5):285–290. https://doi.org/10.1111/j.1365-2591.2005.00930.x

11. Mohammadi Z., Shalavi S., Yaripour S., Kinoshita J.I., Manabe A., Kobayashi M. et al. Smear layer removing ability of root canal irrigation solutions: A review. J Contemp Dent Pract. 2019;20(3):395–402. https://doi.org/10.5005/jp-journals-10024-2528

12. Menezes A.C., Zanet C.G., Valera M.C. Smear layer removal capacity of disinfectant solutions used with and without EDTA for the irrigation of canals: a SEM study. Pesqui Odontol Bras. 2003;17(4):349–355. https://doi.org/10.1590/s1517-74912003000400010

13. Charlie K.M., Kuttappa M.A., George L., Manoj K.V., Joseph B., John N.K. A scanning electron microscope evaluation of smear layer removal and antimicrobial action of mixture of tetracycline, acid and detergent, sodium hypochlorite, ethylenediaminetetraacetic acid, and chlorhexidine gluconate: An in vitro study. J Int Soc Prev Community Dent. 2018;8(1):62–69. https://doi.org/10.4103/jispcd.JISPCD_379_17

14. Khabadze Z., Generalova Y., Kulikova A., Podoprigora I., Abdulkerimova S., Bakaev Y. et al. Irrigation in endodontics: polyhexanide is a promising antibacterial polymer in root canal treatment. Dent J. 2023;11(3):65. https://doi.org/10.3390/dj11030065

15. Torabinejad M., Khademi A.A., Babagoli J., Cho Y., Johnson W.B., Bozhilov K. et al. A new solution for the removal of the smear layer. J Endod. 2003;29(3):170–175. https://doi.org/10.1097/00004770-200303000-00002

16. Aktener B.O., Bilkay U. Smear layer removal with different concentrations of EDTA-ethylenediamine mixtures. J Endod. 1993;19(5):228–231. https://doi.org/10.1016/S0099-2399(06)81296-3

17. Scelza M.F., Pierro V., Scelza P., Pereira M. Effect of three different time periods of irrigation with EDTA-T, EDTA, and citric acid on smear layer removal. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004;98(4):499–503. https://doi.org/10.1016/j.tripleo.2004.03.027

18. Calt S., Serper A. Smear layer removal by EGTA. J Endod. 2000;26(8):459–461. https://doi.org/10.1097/00004770-200008000-00007

19. Torabinejad M., Cho Y., Khademi A.A., Bakland L.K., Shabahang S. The effect of various concentrations of sodium hypochlorite on the ability of MTAD to remove the smear layer. J Endod. 2003;29(4):233–239. https://doi.org/10.1097/00004770-200304000-00001