Reduction of dual‐species biofilm after sonic‐ or ultrasonic‐activated irrigation protocols: A laboratory study

Abstract

Aim To evaluate the antibacterial effect of sonic‐ and ultrasonic‐activated irrigation on bacterial reduction of a dual‐species biofilm in root canals compared to nonactivated irrigation in a laboratory study. Methodology Two hundred and forty extracted human single‐rooted maxillary anterior teeth were divided into two main groups (G, n = 120) according to the initial preparation size of the root canal (G1: size 25, 0.06 taper, G2: size 40, 0.06 taper). Root canals were inoculated with Enterococcus faecalis and Streptococcus oralis. After 5 days, G1 received combined instrumentation (up to size 40, 0.06 taper) and irrigation/activation, whereas G2 received solely irrigation/activation protocols. In both groups, irrigation was performed with sodium hypochlorite (NaOCl 1%) or physiological saline (NaCl 0.9%), using nonactivated syringe irrigation, sonic activation (2 x 30 s) or ultrasonic activation (2 x 30 s). Logarithmic reduction factors (LRFs) of colony‐forming units were analysed separately for dentine‐adherent and planktonic bacteria immediately after irrigation/activation protocols (time‐point 1) or after 5 days of further incubation (time‐point 2) by analysis of variance (anova) and post hoc tests (Tukey's HSD, t‐test). The significance level was set at 0.05. Results In G1 subgroups (combined instrumentation with irrigation/activation), LRFs were significantly affected by the applied irrigation solution (p < .0001), but not by the activation method (p > .05; anova). In G2 subgroups (solely irrigation/activation), both, irrigant solution and activation, significantly affected LRFs (p < .0001, anova). Sonic activation resulted in significantly higher LRFs than ultrasonic activation (p < .0001) which had significantly greater reductions than nonactivated irrigation (p < .05; Tukey's HSD). At T2, strong bacterial regrowth was observed in all groups; however, a significant bacterial reduction was detected for factors instrumentation, irrigant solution and activation (p < .0001; anova). Similar LRFs were found for dentine‐adherent and planktonic bacterial cells in all groups (r = 0.91 at T1, r = 0.8 at T2). Conclusions In this laboratory study on extracted maxillary anterior teeth high‐frequency sonic activation resulted in a greater bacterial reduction compared to ultrasonic activation in groups receiving solely irrigation/activation protocols; however, irrigation using NaOCl and ultrasonic activation also contributed significantly to bacterial reduction compared to the control groups.

Biofilm in Endodontics: In Vitro Cultivation Possibilities, Sonic-, Ultrasonic- and Laser-Assisted Removal Techniques and Evaluation of the Cleaning Efficacy

“…Bhuva et al (2010) demonstrated that ultrasonic irrigation with NaOCl is superior to saline needle/syringe irrigation in biofilm removal at all three levels of the root canal [ 19 ]. Comparatively, other studies noted similar results, although the evaluation method of biofilm removal was different and included plate counting (CFU method) [ 41 , 44 , 45 ]. In addition, it was shown that ultrasonic NaOCl irrigation offers better bacterial reduction than ultrasonic irrigation with water or saline, which can be explained by the antimicrobial effect of NaOCl [ 30 , 33 ].…”

“…According to the reviewed articles, potential double origins, lab-adapted strains [ 15 , 16 , 18 , 19 , 20 , 21 , 24 , 26 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] and clinically isolated E. faecalis were noted [ 25 ]. Types of E. faecalis strains which are most widely used by different authors and bacteria origin are shown in Table 1 .…”

“…The majority of research included in this paper uses human [ 15 , 16 , 18 , 19 , 21 , 22 , 24 , 25 , 27 , 30 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 49 , 53 , 54 ] and animal-bovine dentin [ 20 , 55 ] as substrate for biofilm growth and formation ( Table 1 ).…”

Optimized protocol for collecting root canal biofilms for in vitro studies

“…The traditional method of collecting bio lm using sterilized absorbent paper points has limitations in accessing the entire root canal structure, resulting in aws in the bacterial sampling step (Swimberghe, Coenye, et al, 2019;Hoedke et al, 2021;Al rdous et al, 2022). The inherent limitation of this method is its tendency to predominantly capture planktonic bacteria while failing to effectively retrieve bio lmassociated bacteria (Neelakantan et al, 2015;Neuhaus et al, 2016).…”

Present status and future directions – irrigants and irrigation methods

“…This is rarely feasible, so very frequent wall contact is inevitable (Jiang et al, 2010a) and a large portion of the cleaning and disinfection produced in the main root canal in vitro and ex vivo may be due to this direct physical effect rather than irrigant agitation. Clearly, such an effect cannot reach beyond the main root canal and seems to be redundant when preceded by mechanical preparation and syringe irrigation (Hoedke et al, 2021). Tip‐to‐wall contact also dampens the oscillation and, contrary to commonly held belief (Haapasalo et al, 2012), these plastic tips are also able to cut dentin and create a smear layer (Kanaan et al, 2020).…”