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Year : 2023  |  Volume : 26  |  Issue : 1  |  Page : 31-35
Influence of different irrigant activation methods on apical debris extrusion and bacterial elimination from infected root canals

Department of Conservative Dentistry and Endodontics, Krishnadevaraya College of Dental Sciences, Bengaluru, Karnataka, India

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Date of Submission28-Jun-2022
Date of Decision28-Jul-2022
Date of Acceptance19-Aug-2022
Date of Web Publication08-Dec-2022


Introduction: The study aimed to determine the apical debris extrusion and microbial elimination from infected root canals after using different irrigant activation methods.
Materials and Methods: Forty freshly extracted human mandibular premolars were selected and randomly assigned to four groups (n = 10). The teeth were mechanically prepared, sterilized, and inoculated with Enterococcus faecalis for 1 week. Irrigation was done with 3% sodium hypochlorite following conventional syringe irrigation–Group 1, manual dynamic agitation (MDA)–Group 2, passive ultrasonic irrigation (PUI)-UltraX –Group 3, and sonic irrigation (SI)-EndoActivator -Group 4, and the extruded debris were collected using Myers and Montgomery model. The microbial samples were taken from the canals using sterile paper points, cultured and recorded as colonies. The amount of extruded debris was measured by subtracting the final weight of the Eppendorf tube with debris from the initial weight of the tube.
Results: I. Group 3 showed the least apical debris extrusion (P < 0.05), followed by Groups 2 and 1 and the highest with Group 4. II. Group 3 showed the least colony-forming units (CFUs)/ml, followed by Group 4, and finally, Group 2 showed lesser mean CFUs/ml compared to Group 1 (P < 0.05).
Conclusion: All the irrigation activation methods were associated with apical debris extrusion, with the PUI system extruding the least amount of debris compared to the other groups. Irrigation activation techniques were beneficial in reducing the microbial load from the infected canals with the PUI system showing a complete elimination of the microbes, followed by SI and MDA.

Keywords: Apical extrusion; manual dynamic agitation; microbial elimination; passive ultrasonic irrigation; sonic irrigation

How to cite this article:
Ada K S, Shetty S, Jayalakshmi K B, Nadig PL, Manje Gowda P G, Selvan AK. Influence of different irrigant activation methods on apical debris extrusion and bacterial elimination from infected root canals. J Conserv Dent 2023;26:31-5

How to cite this URL:
Ada K S, Shetty S, Jayalakshmi K B, Nadig PL, Manje Gowda P G, Selvan AK. Influence of different irrigant activation methods on apical debris extrusion and bacterial elimination from infected root canals. J Conserv Dent [serial online] 2023 [cited 2023 Dec 6];26:31-5. Available from:

   Introduction Top

Endodontic treatment encompasses thorough cleaning and shaping of the canal through appropriate instrumentation and irrigation. Surpassing emphasis is placed on irrigation as up to 35% of the root canal wall remains unistrumented.[1],[2] Sodium hypochlorite is considered the gold-standard irrigant owing to its tissue dissolution and broad-spectrum antimicrobial activity.[3],[4],[5] It can substantially reduce the number of microbes within the superficial layers, but pathogens have been found residing at depths of up to 420 μm, and studies have demonstrated that conventional irrigation allows hypochlorite penetration only up to 250 μm into root dentine.[1] Hence, the aforementioned limitations could be overcome through the use of different irrigant activation techniques. Manual dynamic agitation (MDA) involves repeatedly inserting a well-fitting gutta-percha cone to the working length (WL) of an instrumented canal to produce hydrodynamic displacing forces within irrigants. Passive ultrasonic irrigation (PUI) uses freely oscillating files at ultrasonic frequencies (25–30 KHz) to generate acoustic cavitation and streaming forces. Sonic irrigation (SI) creates a hydrodynamic phenomenon within irrigants by oscillating a smooth flexible polymer file at frequencies of 1–10 kHz.

During biomechanical preparation and irrigation, there may be extrusion of bacteria, dentinal debris, necrotic tissue, and irrigants into the periradicular space.[6],[7] This extruded material, referred to as the “worm of necrotic debris,” possesses the potential to disrupt the equilibrium between microbial aggression and host defense, ensuing acute inflammation and flare-ups.[6],[8]

Hence, to avoid flare-ups, every effort should be made to decrease apical extrusion of infected debris and outright elimination of microbial load to minimize postoperative reactions.

Therefore, this study aimed to determine the apical debris extrusion and microbial elimination from infected root canals after using different irrigant activation methods.

   Materials and Methods Top

Forty freshly extracted human mandibular premolars were selected. The inclusion criteria were single root with a single canal and one apical foramen with a mature closed apex. Radiographs were taken from different angulations for the evaluation of root morphology. Soft-tissue remnants and calculus on the external root surface were removed by scaling. Access cavities were prepared in all the teeth, and canal patency was established with a size 10K file (Dentsply Sirona, Ballaigues, Switzerland). The WL was measured by inserting a size 10K file until the tip was visible just beyond the apex under magnification and 1 mm was subtracted from this length. All the canals were enlarged to this WL as per the manufacturer's recommendation sequentially up to a size of F2 ProTaper Gold rotary file (size 25-0.08). During instrumentation, 1 ml of 3% NaOCl was administered between files.

The foramen was then sealed with resin-epoxy material to prevent bacterial leakage. The specimens were then sterilized in an autoclave for 20 min at 121°C.

Specimen contamination

Enterococcus faecalis derived from ATCC29212 was obtained and cultured aerobically on blood agar at 35°C for 48 h. Colonies were grown in brain heart infusion (BHI) broth at 37°C for 24 h. Inoculum was prepared in sterile BHI broth; turbidity was set to 0.5 McFarland corresponding to approximately 1.5 × 108 colony-forming units (CFUs/ml). A total of 10 μl of the culture was immediately inoculated into the canals, and the teeth were placed in sterile cups and incubated for seven days. Inoculum was renewed daily for seven days to ensure maintenance of culture viability. Four teeth were randomly selected for enumeration of E. faecalis directly after inoculation.

Myers and Montgomery experimental model

A previously described model by Myers and Montgomery was used for apical debris collection. Eppendorf tubes with their own stoppers were weighed in an electronic weighing machine (Mettler AJ 100, Greifensee, Switzerland) which had an accuracy of 0.0001 g. Three consecutive weights were obtained for each Eppendorf tube, and the average measurement was taken to be its initial weight. Separate rubber stoppers were made for each Eppendorf tube which had a tight fit to its opening, and holes were created on these stoppers such that teeth could be inserted up to the cementoenamel junction, and a 21-G needle was placed alongside the rubber stopper to equalize the internal and external air pressure. These setups were then placed into preweighed Eppendorf tubes, and the tubes were fitted into glass vials [Figure 1].
Figure 1: Myers and Montgomery model

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Irrigant activation

After the incubation period, the root canals were divided into four groups, n = 10.

  • Group 1 (conventional syringe irrigation): Irrigation was performed with a syringe and a 27-gauge side-vented needle (Canal clean, Biodent, South Korea). The irrigation needle was placed 1 mm short of WL, and the canals were irrigated using 2 ml of 3% sodium hypochlorite for 2 min
  • Group 2 (MDA): A single ProTaper F2 GP cone (Dentsply Sirona) was repeatedly inserted into WL with short 2–3 mm longitudinal push–pull strokes for 60 s at a rate of 100 strokes per minute
  • Group 3 (PUI): Irrigation procedure was performed using the same needle that was utilized in conventional syringe irrigation. An ultrasonic tip (size 20, 0.02 taper) (UltraX, Eighteeth, Orikam) was placed 1 mm short of the WL and activated for 1 min
  • Group 4 (SI): An EndoActivator device (Dentsply Sirona) was activated for 1 min with a size 20/.02 polymer tip 1 mm short of the WL.

Microbial analysis

Following irrigation activation, after drying the root canals, E. faecalis count was evaluated by placing a sterile paper point into each canal for 5 min. Paper points were then placed in 500 μL of sterile BHI broth contained in Eppendorf tubes for 15 min. After mixing by vortex, 50 μL of the liquid medium was serially diluted in sterile BHI broth and plated on agar plates. Culture media was then placed in an incubator at 37°C for 48 h, following which colonies were counted.

Debris collection

After the microbial analysis, each tooth with its corresponding rubber stoppers was removed from the Eppendorf tubes, and the debris adhering to the root surface was collected by washing the root surface with 1 ml of distilled water into the Eppendorf tube. Subsequently, the tubes were stored in an incubator at 37°C for 10 days to evaporate the irrigant before weighing the dry debris. After the incubation period, the Eppendorf tubes were weighed three times using the same electronic weighing machine to obtain the final mean weight. The dry weight of debris was calculated by subtracting the weight of the empty tube from that of the tube containing the extruded debris.

Statistical analysis

Kruskal–Wallis test followed by Mann–Whitney posthoc analysis was performed to compare the mean Apical Debris Extruded and CFUs/ml among four study groups. The level of significance was set at P < 0.05. SPSS software (Version 22.0 Released 2013. Armonk, NY, USA: IBM Corp.,) was used to analyze the data.

   Results Top

Group 1– Conventional Syringe irrigation ; Group 2– Manual Dynamic Agitation; Group 3– Ultrasonic irrigation (UltraX), and Group 4– Sonic irrigation (EndoActivator).

[Table 1] illustrates the comparison of the mean apical debris extruded among four groups. This mean difference in the apical debris extruded among four groups was statistically significant at P < 0.001.
Table 1: Comparison of the mean Apical Debris Extruded among 4 groups using Kruskal–Wallis test

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[Table 2] illustrates the multiple comparison of the mean differences in apical debris extruded among four groups.
Table 2: Multiple comparison of the mean difference in Apical Debris Extruded among 4 groups using Mann–Whitney posthoc test

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The test results showed that Group 3 showed significantly the least mean apical debris extruded at P < 0.001, followed by Groups 2 and 1 and the highest with Group 4.

[Table 3] illustrates the comparison of mean CFUs/ml among four groups.
Table 3: Comparison of the mean colony-forming units (104)/mL among 4 groups using Kruskal–Wallis test

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This mean difference in the CFUs/ml among the four groups was statistically significant at P < 0.001.

[Table 4] illustrates the multiple comparisons of mean differences in CFUs/ml among four groups.{Table }

The test results showed that Group 3 demonstrated significantly lesser CFUs/ml compared to Groups 1 and 2 at P = 0.002 and P = 0.03, respectively. This was followed by Group 4 and finally, Group 2 showed significantly lesser mean CFUs/ml compared to Group 1 at P = 0.02.

However, no statistically significant difference was noted between Groups 2 and 4 (P = 0.38) and between Groups 3 and 4 (P = 0.07).

   Discussion Top

During root canal preparation, there may be extrusion of bacteria, dentinal debris, necrotic tissue, and irrigants into the periradicular region.[6],[7] Extrusion of debris beyond the apical foramen leads to the increased influx of exudates and blood into the canal, which enhances the nutritional supply for the bacteria and exacerbates a chronic lesion, leading to “flare-ups.”[8]

Sodium hypochlorite was used as an irrigant in this study. The inadvertent extrusion of NaOCl can cause severe soft-tissue irritation and necrosis and can compromise the integrity of cancellous bone; therefore, its use should be restricted within the confines of the root canal.[9],[10]

In the present study, an experimental model described by Myers and Montgomery in 1991 [Figure 1] was used for debris collection. Others like Hachmeister et al. suggested the use of floral foam and agar gel methods to simulate the back pressure provided by periapical tissues.[9],[11] However, these methodologies have also been criticized as floral foam may absorb irrigants and debris while acting as a barrier, and adjusting the thickness of the agar gel may be difficult.[9],[11],[12] Consequently, vital periapical tissues were not mimicked, so the results may not be the same as an in vivo model.[9],[13] In addition, the defense mechanism of the body cannot be mimicked in a laboratory set-up.[8] Hence, it is not entirely plausible to extrapolate the results to the clinical situation.

In the current study, we tried to simulate the distinctive clinical scenario of canal superinfection by renewing the inoculum daily for a week, as it is investigated that when a tooth is infected, the pathology can easily augment if the cause is not treated.[14],[15]

The various irrigation activation systems used in this study caused apical extrusion of debris. This result is in accordance with the other studies.[2],[9],[11],[16] Previous studies showed that side-vented needles extruded less debris.[17],[18],[19] Therefore, in the present study, closed-end tip and side-port opening needles were used. When using needle irrigation, irrigant penetration was limited to only 1–1.5 mm apical to the needle tip. Hence, the needle should be placed within 1 mm from WL to ensure fluid exchange. However, this recommendation is unsafe, because intracanal pressure produced by small-diameter needles can reach up to 400–550 KPa, which can contribute to the possibility of extrusion of irrigant into periradicular tissues or even create an apical vapor lock effect.[20],[21]

During ultrasonic activation, energy is transmitted through ultrasonic waves and can produce acoustic streaming and cavitation; this causes deagglomeration of bacterial biofilms through the acoustic streaming action.[11] The intensity of acoustic streaming depends on frequency and displacement amplitude at the end of the file.[22] The shear stress and hydrodynamic pressure generated during PUI irrigation were significantly greater and more evenly distributed across a larger area of the canal wall (Chen et al. 2014).[1] This contributed to the least debris extrusion in PUI [Table 1].

The sonic system has 3D motion; this motion combined with the system's frequency and more flexible tips delineate that sonic caused significantly a higher amount of debris extrusion than other groups in the present study.[11] When the movement of the sonic file is constrained, the sideways movement will disappear but will result in a longitudinal vibration (Lumley et al. 1996).[22] Sonic activation is purportedly less effective than ultrasound, as a more velocious fluid stream is induced with the latter.[14]

The difference in bacterial elimination between EndoActivator and UltraX may be attributed to the driving frequency of the ultrasonic device which is higher than that of the sonic device.[5] The positive relationship between streaming velocity and frequency can explain the higher efficiency of PUI versus SI.[22] A higher frequency ensures a higher flow velocity of the NaOCl irrigant resulting in a better bacterial elimination by PUI than EndoActivator[5] [Table 3]. The difference between MDA and EndoActivator may be attributed to the fact that manual push–pull motion of the gutta-percha generates frequency less efficient than the automated methods.[5]

In contrast to the current study, Boutsioukis et al. concluded that MDA extruded more irrigant compared to sonic and ultrasonic agitation.[2] Authors attributed the finding to the fact that oscillating instruments generate a lateral flow toward the canal wall, while a moving gutta-percha cone results in a flow with a considerable component in the apical direction.[2] The results of another study by İnce Yusufoglu et al. were in accordance with the current study, wherein the EDDY sonic system caused the maximum debris extrusion while PUI caused the least extrusion among PIPS, manual irrigation, and EDDY system.[11] The results of a study conducted by Mohmmed and Mahdee on organic film removal were also in compliance with the current study, wherein EndoActivator agitation is more effective in biofilm removal than gutta-percha pumping but less effective than passive ultrasonic agitation.[5] Therefore, a wide range of complex variations in root canal anatomy including root canal configuration type, developmental anomalies, accessory canals, and apical deltas can be rendered clean only by the implementation of the various irrigant activation protocols.[23]

   Conclusion Top

  • All the irrigation activation methods were associated with apical extrusion of debris, with the PUI system extruding significantly the least amount of debris, and the highest debris extrusion was observed in the SI group compared to the other groups
  • Irrigation activation techniques were beneficial in reducing the microbial load from the infected canals with the PUI system showing a complete elimination of the microbes, followed by SI and MDA.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Virdee SS, Farnell DJ, Silva MA, Camilleri J, Cooper PR, Tomson PL. The influence of irrigant activation, concentration and contact time on sodium hypochlorite penetration into root dentine: An ex vivo experiment. Int Endod J 2020;53:986-97.  Back to cited text no. 1
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.  Back to cited text no. 2
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;36:1558-62.  Back to cited text no. 3
Poggio C, Arciola CR, Dagna A, Chiesa M, Sforza D, Visai L. Antimicrobial activity of sodium hypochlorite-based irrigating solutions. Int J Artif Organs 2010;33:654-9.  Back to cited text no. 4
Mohmmed S, Mahdee A. Assessment of the effect of three agitation techniques on the removal efficacy of sodium hypochlorite for the organic films. World J Dent 2019;10:440-44.  Back to cited text no. 5
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Correspondence Address:
Dr. K Sadia Ada
No: 209 Commanders Pinnacle Apartment, Central Telecom Society, Bengaluru - 562 157, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_378_22

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  [Table 1], [Table 2], [Table 3], [Table 4]


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