Optimizing irrigation — consider the possibilities

Dr. Rich Mounce discusses trends for creating cleaner canals

The ideal goal of endodontic canal cleaning is to eliminate the smear layer, biofilms, bacteria, clean tubules, and remove all tissue (from orifice to apex). With the current state of the art, this remains an ideal goal not yet realized. This column was written to highlight the current state of the art in endodontics. Presently, there is no literature-based superiority of endodontic irrigation regimens, only trends that are correlated in the literature with creating cleaner canals. Collectively though, there are literature-based irrigation techniques that provide cleaner canals.  

In general terms, optimizing the following variables leads to cleaner canals: irrigant combinations using a bactericidal agent and smear layer removal agent; greater irrigant volumes; greater concentrations; increased contact times; reduced surface tension; increased temperature; improved apical delivery (with regard to needle type and depth of insertion); and irrigant activation (multisonic, laser, negative pressure, ultrasonic, plastic file agitation, and so on). Eloquently summarized by Stojicic, et al., 2010, “Optimizing the concentration, temperature, flow, and surface tension can improve the tissue-dissolving effectiveness of hypochlorite even 50-fold.” Clinically, the above notwithstanding, no one single variable is primary in creating optimal canal cleanliness using the technology available at this time.

Among many possible literature choices, highlights from the endodontic literature illustrating current state-of-the-art thought include the following. 

All things being equal, sodium hypochlorite (SH) is the irrigant of choice. SH is more effective than 2% chlorhexidine (CHX) to eliminate biofilms (Del Carpio-Perochena, et al., 2011). 

CHX retains its antimicrobial activity for at least a week after use clinically. SH does not possess this ability, yet obviously can dissolve tissue, which CHX cannot. (Dametto, et al., 2005; Rosenthal, et al., 2004). 

Increasing the master apical diameter and placing the irrigating needle near the TWL are required for irrigant replacement apically. How deeply the irrigating needle is inserted is significant, with a deeper insertion more effective than one more distant from the apex. Sedgley, et al., 2005; Hsieh, et al., 2007 found “With a final apical size of 35, a 27-gauge needle would need to penetrate to within 3 mm of working length for irrigant flow.” 

Stojicic, et al., 2010 also stated: “Weight loss (dissolution) of the tissue increased almost linearly with the concentration of sodium hypochlorite. Higher temperatures and agitation considerably enhanced the efficacy of sodium hypochlorite. The effect of agitation on tissue dissolution was greater than that of temperature; continuous agitation resulted in the fastest tissue dissolution. Hypochlorite with added surface active agent had the lowest contact angle on dentin and was most effective in tissue dissolution in all experimental situations.” 

 Optimized taper helps optimize irrigant delivery. Correlating master apical diameter and canal taper, Brunson, et al., 2010 found: “An increase from ISO #35 to ISO #40 resulted in a percentage gain of approximately 44% in mean irrigant volume …” and “an increase in taper from 0.02 through 0.08 resulted in percentage gains of approximately 74%, 5.4%, and 2.4% increase (of irrigant volume), respectively.” 

Activation is an essential part of endodontic cleaning relative to syringe only irrigation (Kuah, et al., 2009; Chopra, et al., 2008; Gutarts, et al., 2005). 

Finally, a new and novel multisonic cleaning technique is on the horizon (while not yet commercially available at this time): the GentleWave™ technology from Sonendo^®, whose first examination in the scientific literature has just been published (Haapasalo, et al., 2014). Haapasalo, et al., concluded, “The novel Multisonic Ultracleaning System achieved a significantly faster tissue dissolution rate when compared with the other systems examined in vitro.” If Sonendo’s full promise is realized, complex instrumentation regimens can become a thing of the past as the device is capable of reaching inaccessible areas of the canal to remove biofilm, tissue, bacteria, the smear layer, and clean tubules to an extent never before seen predictably. 

This column was written to highlight the current literature-based state of the art in endodontic irrigation. While not by any means exhaustive, it highlights the importance of optimizing all of the variables possible in cleaning canals once they are shaped. 

References

1. Brunson M, Heilborn C, Johnson DJ, Cohenca N. Effect of apical preparation size and preparation taper on irrigant volume delivered by using negative pressure irrigation system.  J Endod. 2010;36(4):721-724.

2. Chopra S, Murray PE, Namerow KN. A scanning electron microscopic evaluation of the effectiveness of the F-file versus ultrasonic activation of a K-file to remove smear layer. J Endod. 2008;34(10):1243-5.

3. Dametto FR, Ferraz CC, Gomes BP, Zaia AA, Teixeira FB, de Souza-Filho FJ. In vitro assessment of the immediate and prolonged antimicrobial action of chlorhexidine gel as an endodontic irrigant against Enterococcus faecalis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005;99(6):768-772.

4. Del Carpio-Perochena AE, Bramante CM, Duarte MA, Cavenago BC, Villas-Boas MH, Graeff MS, Bernardineli N, de Andrade FB, Ordinola-Zapata R. Biofilm dissolution and cleaning ability of different irrigant solutions on intraorally infected dentin. J Endod. 2011;37(8): 1134-1138.

5. Gutarts R, Nusstein J, Reader A, Beck M. In vivo debridement efficacy of ultrasonic irrigation following hand-rotary instrumentation in human mandibular molars. J Endod. 2005;31(3):166-70.

6. Haapasalo M, Wang Z, Shen Y, Curtis A, Patel P, Khakpour M. Tissue dissolution by a novel multisonic ultracleaning system and sodium hypochlorite. J Endod. [online] February 17, 2014. Available at: https://www.jendodon.com/article/S0099-2399%2814%2900005-3/abstract. Accessed June 19, 2014.

7. Hsieh YD, Gau CH, Kung Wu SF, Shen EC, Hsu PW, Fu E. Dynamic recording of irrigating fluid distribution in root canals using thermal image analysis. Int Endod J. 2007;40(1):11-7.

8. Kuah HG, Lui JN, Tseng PS, Chen NN. The effect of EDTA with and without ultrasonics on removal of the smear layer. J Endod. 2009;35(3):393-396.

9. Rosenthal S, Spångberg L, Safavi K. Chlorhexidine substantivity in root canal dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2004;98(4):488-492.

10. Sedgley CM, Lennan SL, Appelbe OK. Survival of Enterococcus faecalis in root canals ex vivo. Int Endod J. 2005;38(10):735-742.

11. Stojicic S, Zivkovic S, Qian W, Zhang H, Haapasalo M. Tissue dissolution by sodium hypochlorite: effect of concentration, temperature, agitation, and surfactant. J Endod. 2010;36(9):1558-1562.