Skip to main content
Download PDF

Efficacy evaluation of a cordless ultrasonic unit in achieving reduction of bacterial load within a root canal system as compared to a conventional ultrasonic unit and negative pressure irrigation

Evidence-Based Endodontics volume 4, Article number: 2 (2019) Cite this article

Abstract

Introduction

Increase in efficacy during root canal irrigation may contribute to better treatment outcomes. This study investigated the efficacy of ultrasonic and negative pressure irrigation systems using sodium hypochlorite (NaOCl) in the reduction of bacterial load in human teeth.

One hundred thirty-one single-rooted teeth were cleaned and shaped, autoclaved, and incubated with E. faecalis. Teeth were randomly assigned to three experimental groups (n = 40) and treated in the presence of 1% sodium hypochlorite using EndoUltra cordless ultrasonic, conventional ultrasonic, and Endovac negative pressure irrigation. Syringe irrigation controls were treated with 1% sodium hypochlorite and phosphate-buffered saline via side-vented needle irrigation. All groups with NaOCl received 5% sodium thiosulfate neutralization for 5 min after treatment. Samples of root canal fluid and dentin chips were acquired from canals before and after treatment, incubated on BHI agar, and colony forming units categorized according to quantity. Wilcoxon rank-sum and Bonferroni tests were used for statistical analysis. p values less than 0.05 were considered significant.

Results

Endovac group was significantly better in eliminating bacteria from the root canals than 1% NaOCl (p = 0.006) and PBS syringe irrigation (p = 0.015). However, it was not significantly different from the two ultrasonic groups (p > 0.05). Both ultrasonic groups showed better performance than 1% NaOCl and PBS syringe irrigation, however, not statistically significant (p < 0.03). There was no significant difference between the two ultrasonic devices (p > 0.05).

Conclusion

EndoVac may be an important tool for bacterial load reduction in oval canals.

Introduction

Bacterial persistence at the time of root canal obturation in endodontically treated teeth is a risk factor for post-treatment apical periodontitis (Siqueira Jr. and Rocas 2008). Intracanal biofilms and smear layer residues harboring bacterial pathogens contribute to apical periodontitis development (Kakehashi et al. 1965; Ricucci and Siqueira Jr 2010; Siqueira Jr 2001). Biofilms and smear layer are often incompletely removed by mechanical instrumentation techniques; conventional hand and rotary instruments may miss root canal surfaces located in ovals, fins, accessory canals, isthmus, and associated intricacies (Paque et al. 2010; Dalton et al. 1998; Hubscher et al. 2003; Peters 2004).

Irrigants can bridge the gap of disinfection and tissue removal by reaching into these difficult to access areas (Park et al. 2012). Therefore, improvement of irrigant effectiveness in reducing bacterial loads should be an important goal in endodontic treatment (Siqueira Jr. and Rocas 2008; Chrepa et al. 2014).

Sodium hypochlorite (NaOCl) is the most commonly used endodontic irrigant (Mohammadi 2008). This solution has the advantage of functioning as intracanal disinfection while enabling the dissolution of residual tissue. However, a major disadvantage it carries is the toxicity caused to tissues when the high concentrations are extruded beyond the canal space (Guivarc'h et al. 2017; Kleier et al. 2008). Traditionally, manual syringe needle irrigation of the canal space has been used to deliver NaOCl into the root canal. This method is not efficient in the removal of bacterial biofilm and debris from the apical part of the canal (Ordinola-Zapata et al. 2014).

Enterococcus faecalis, a Gram-positive pathogen, plays a major role in the etiology of persistent periradicular lesions after root canal treatment and is commonly found in a high percentage of root canal failures (Siqueira Jr. and Rocas 2008; Portenier et al. 2003; Barbosa-Ribeiro et al. 2016; Stuart et al. 2006; Evans et al. 2002). Therefore, the E. faecalis root canal infection is considered an appropriate model for testing novel antimicrobial treatments (Rosen et al. 2016).

Various techniques were reported to improve the NaOCl efficacy to reduce bacterial loads within the root canal system, such as ultrasonic activation, temperature increase of the NaOCl solution, and negative pressure volume replenishment (Park 2013; Basrani and Haapasalo 2012; Zehnder 2006). Ultrasonic activation is defined as device operation at vibration frequencies of 20 kHz or more, with dental devices ranging from 25 to 42 kHz (Ahmad et al. 1987). Ultrasonic irrigation activation methods involve the two main principles of action: acoustic streaming and cavitation (Macedo et al. 2014; Ahmad et al. 1987; Ahmad et al. 1987b).

The EndoUltraâ„¢ (Vista US, Racine, WI) is a new ultrasonic device that has been developed with miniaturized piezoelectric technology that enables an operating frequency of 40 kHz. As the EndoUltraâ„¢ is a compact handheld cordless design, it may offer a convenient alternative to conventional ultrasonic activators (Lloyd et al. 2016).

Another irrigation technique is the negative pressure system. This procedure involves replenishing, exchange, and circulation of a low concentration of NaOCl. The method may increase the irrigation effectiveness and compensate for lower concentrations of the solution, potentially reducing solution toxicity (Moorer and Wesselink 1982). In the negative pressure technique, a fresh solution is delivered and the spent solution and debris are removed in a circulatory manner via an apically directed current. An example of negative pressure replenishment circulation technology is the EndoVac system (Kerr, Orange CA).

The aim of this study is to evaluate the efficacy of the EndoUltraâ„¢ cordless ultrasonic system and the negative pressure irrigation (EndoVac) in comparison to the conventional ultrasonic irrigation by determining the reduction of bacterial loads in human teeth.

Materials and methods

Tooth specimens

One hundred thirty-six previously extracted human single-rooted teeth with a single canal were collected from the University of Texas School of Dentistry Oral and Maxillofacial Surgery and Periodontics Clinics. The teeth were extracted due to periodontal or restorative reasons. The study (HSC-DB-16-0871) was reviewed and approved by the Committee for the Protection of Human Subjects (CPHS) of the institution.

All teeth were inspected using a dental microscope (Global Dental Microscope .5× with Led illumination St. Louis, MO). Two periapical radiographs were taken for each tooth from buccal-lingual and mesial-distal projections. Only single-rooted anterior teeth with a single-root canal were used in this study.

The following exclusion criteria were applied: teeth with multiple roots, multiple canals, immature roots, teeth with open apices, fractured roots, internal or external resorption, calcified canals, dentinal cracks, or fracture lines, root caries. All teeth were stored in phosphate-buffered saline (PBS) until used.

Specimen preparation

The crowns of the teeth were removed by a diamond disk (Kerr Orange, CA) to acquire roots 16 mm in length

A 15 K file (Kerr. Orange, CA.) was fitted inside the canal until the file tip was just visible at the apical foramen. One millimeter was subtracted to confirm the working length of 15 mm. The canals were instrumented with a TF Adaptive NiTi Endo File System (Kerr, Orange, CA) following the manufacturer’s instructions to a 35/.04 apical preparation; 6% NaOCl was used as an irrigant solution.

Smear layer removal and sterilization

Upon completion of instrumentation, NaOCl was inactivated with 5% sodium thiosulfate for 5 min followed by irrigation with 5 mL of 17% EDTA for one minute. A closed canal system was adopted according to Tay (Tay et al. 2010).

A random sample of five teeth was selected as a control to verify the cleanness of the root canal and smear layer removal. The teeth were prepared as following: the roots were splitted longitudinally using a diamond disk (Kerr Orange, CA) without passing the disk through the root canal lumen under constant cooling with water to prevent accumulation of dentinal debris. A chisel and small hammer were used to split the root into two halves. Once the roots were separated, they were dehydrated using an ascending series of ethanol concentrations and t-butanol. The roots were allowed to dry in a desiccator and subsequently sputter-coated (Cressington 208HR) with a 7 nm of gold. The root canal surfaces were examined using a scanning electron microscopy (FEI Nova Nano SEM 230, Austin, TX) in order to evaluate smear layer removal. The criterion for complete smear layer removal was to be able to observe complete opening of dentinal tubules in the apical middle and coronal portion of the root at a magnification of ×1000.

All the experimental specimen teeth were then autoclaved for 20 min at 121 °C.

Bacterial load of the prepared root canal specimens

E. faecalis (strain OG1RF) was cultured in 1 mL of brain heart infusion (BHI) for 16 h and inoculated into 5 mL of fresh BHI with 2% glucose solution. The ability to colonize the root canal was verified by observing the root canal surfaces via SEM (n = 5). The specimen root canals were inoculated with 100 μL of the suspension and incubated at 37° for 30 days. The medium was exchanged every 7 days.

Sampling of bacterial growth (S1)

A sterile #35 Hedstrom© file (Maillefer, Tulsa, OK) was inserted to the working length in order to create dentin shavings and sterile Autofit paper points (Kerr Orange. CA) were used to collect the remaining fluid from the infected canals (S1). The threaded file portion and Autofit paper points were collected and placed into Eppendorf microtubes (Fisher Scientific, Pittsburg, PA.) containing 1 mL of PBS. The samples were vortexed for 10 s and 30 μL aliquot samples were spread on BHI agar plates and incubated at 37° for 24 h. Thereafter, the number of colony forming units (CFU) was counted to determine the presence of viable bacteria in the tooth samples.

Experimental groups

Out of 136 roots, 131 prepared specimens infected with E. faecalis were randomly assigned into 5 groups. Five random teeth were selected as a control to verify the cleanness of the root canal and smear layer.

Group 1: (EndoUltraâ„¢ cordless ultrasonic device (Vista US, Racine, WI), n = 40)

Canals were filled with 1% NaOCl (Zehnder 2006) and the ultrasonic irrigation protocol was performed using the supplied irrigation tips as follows: 3 cycles of 20 s, at the end of each cycle, a syringe replenished the solution (total volume = 3 ml). EndoUltra ultrasonic tip was placed 1 mm from the working length.

Group 2: (Satelec P5 Booster® and Irrisafe ™ (Acteon, Mount Laurel, NJ), n = 40)

Canals were filled with 1% NaOCl and the ultrasonic irrigation protocol was performed using #20, 0.02 taper activator as following: 3 cycles of 20 s, at the end of each cycle, a syringe replenished the solution (total volume = 3 ml). Irrisafe Ultrasonic tip was placed 1 mm from the working length.

Group 3: (EndoVac (Kerr, Orange, CA), negative pressure irrigation, n = 40)

Canals were filled with 1% NaOCl and the irrigation was performed in two steps as the following:

  1. a.

    Macro-cannula step:

    One percent NaOCl was constantly delivery for 15 seconds and a macro-cannula was placed approximately to the mid-canal level with up and down (pecking) motion.

  2. b.

    Micro-cannula step:

    The deliver solution was carried into the root canals and pulp chamber using a micro-cannula. Thereafter, the solution was withdrawn by suction and delivered all the way to the working length. The micro-cannula was removed rapidly to prevent the evacuation of the solution from inside of the root canal.

    b1. The root canal was flooded with NaOCl for 10 s and subsequently, it was evacuated using a micro-cannula. (Purge in Endovac language means, evacuate root canal content (solution) completely). Then the root canal was again flooded with NaOCl for 10 s and the micro-cannula was positioned all the way to the working length (total volume = 3 ml; irrigation time = 1 min).

Group 4: (control)—1% NaOCl, n = 9)

Canals were irrigated with 1% NaOCl (total volume = 3 ml, irrigation time = 1 min) using a syringe side-vented needle (Dentsply, Tulsa, OK) with no agitation. The needle was placed 1 mm short of the working length.

Group 5: (negative control, n = 2)

Canals were irrigated with PBS using a syringe side-vented needle (Dentsply, Tulsa, OK). Total volume = 3 ml; irrigation time = 1 min.

For groups 1, 2, 3, and 4, subsequent to the NaOCl treatment, the root canals were flushed with 5 ml 5% sodium thiosulfate for 5 min to inactivate the NaOCl.

Thereafter, for all groups, the canals were filled with PBS and a sterile #35 Hedstrom© file was used to create dentine debris. Samples were collected using a sterile paper point as described previously for bacterial growth and CFU counting (S2).

Statistical analysis

A grading score was assigned to the CFU count for each sample before (S1) and after irrigation procedures (S2) yielding a basis for rank comparison. The CFU counts were quantified by category as very heavy (score = 5), heavy (score = 4), moderate (score = 3), sparse (score = 2), and very sparse (score = 1), and none (no growth, score = 0) on agar plates, corresponding to > 10000, 1001–10000, 101–1000, 1–10, and 0 colony forming units per 0.1 ml transport medium, respectively (Dahlen et al. 1982) (Table 1).

Table 1 The CFU counts quantified by category of growth on agar plates, corresponding to colony forming units per 0.1 ml transport medium
Full size table

Descriptive statistics (frequency and percentage) were provided for the score values of CFU in the 5 groups (Table 2). Wilcoxon rank-sum test was used to compare the grading scores after treatment between the three treatment groups and controls and Bonferroni adjustment was used to adjust for multiple testing. p values less than 0.05 were considered significant. Statistical analysis was performed with SAS 9.4 software (Cary, NC).

Table 2 CFU score percentages according to irrigation technique
Full size table

Results

SEM evaluation of the prepared root canals before bacterial inoculation confirmed smear layer removal and the absence of bacterial growth.

In all the experimental and control groups, there was a heavy presence of bacteria prior to treatment—S1 all scored 5 (CFU > 10000).

Following the treatment, none of the groups had a very heavy bacterial load (CFUs > 10000, score 5). Only groups 4 (1% NaOCl) and 5 (negative control) exhibited heavy bacterial presence (CFUs 1001–10000, score 4). All experimental groups showed moderate bacterial presence (CFUs 101–1000, score 3) or less after treatment. Although certain individual samples from all experimental groups showed no growth, no group as a whole exhibited complete eradication of bacteria.

The Endovac group (group 3) was significantly better in eliminating bacteria from the root canals than the 1% NaOCl control group (group 4), (p = 0.006), and the negative control group (group 5), (p = 0.015). There was no significant difference between the Endovac and two ultrasonic device groups ((group 1, EndoUltra; p = 0.283) and (group 2, conventional US; p = 0.398)) (Fig. 1).

Fig. 1
figure 1

Post-treatment CFU counts quantified by five categories of growth on agar plates, corresponding to colony forming units per 0.1 ml transport medium, ranging from very heavy (score 5) to none (score 0). Post-treatment bacterial growth from canal samples was significantly less for EndoVac than the syringe 1% NaOCl (p = 0.006) and PBS (p = 0.015) techniques, but there was no significant difference between the cordless (p = 0.283) and conventional ultrasonic devices (p = 0.398). There was no difference between the EndoVac negative pressure irrigation and either of the ultrasonic devices (p = 0.0806)

Full size image

There was no significant difference between the two ultrasonic devices (p = 0.806). Furthermore, there was no significant difference between EndoUltra (group 1) and conventional ultrasonic groups (group 2) as compared to 1% NaOCl (group 4, p = 0.03 and p = 0.02, respectively) and PBS syringe irrigation groups (group 5, p = 0.02 for both).

Discussion

In this study, we examined antibacterial efficacy of three irrigation techniques using an extracted tooth model (Wu et al. 2000) E. faecalis is commonly found in cases of persistent apical periodontitis and it was used in the present study due to its ability to form a stable biofilm (Siqueira Jr. and Rocas 2008; Stuart et al. 2006; Duggan and Sedgley 2007; Al-Ahmad et al. 2014).

Cultivable bacteria (CFU) count before and after irrigant treatment has served in previous irrigation studies as an indicator of viable bacteria load reduction (Molander et al. 1998; Shen et al. 2012; Hockett et al. 2008; Spoleti et al. 2003). The volumes and exposure times of the irrigants were equal in all regimens performed to the control for these variables.

The aim of the study was to determine the efficacy of the EndoUltraâ„¢ cordless ultrasonic system and the negative pressure irrigation (EndoVac) relative to the conventional ultrasonic irrigation techniques. Our data suggests EndoUltraTM cordless ultrasonic and conventional ultrasonic groups are not significantly different for each other but differ from the Endovac group in terms of reducing bacterial load. The two ultrasonic devices were not statistically different in terms of reducing bacterial load. This result was expected because the two devices are assumed to operate with similar ultrasonic induced flow patterns. The fact that the two devices are supposed operate at different frequencies (27 to 33 kHz versus 40 kHz) had no effect on the treatment outcome.

In the ultrasonic instrument oscillation, the pressure waves generate acoustic streaming and cavitation. However, the presence and clinical significance of cavitation in ultrasonic irrigation have been debated (Park 2013; Ahmad et al. 1987b; Plotino et al. 2007). Ahmad (Ahmad et al. 1988) did observe cavitation light emissions under sufficient amplitude at the tip of a freely moving file. Nevertheless, the study determined that cavitation was not the important mechanism in debridement. The main flow factor appears to be acoustic streaming. The streaming flow at the end of the instrument can penetrate into the region of spent resident irrigant located at the apical portion of the root canal system. It is this streaming flow that is likely to play an important role in debriding the biofilm-infected apical anatomy (Gulabivala et al. 2010). If any cavitation was produced with the relatively high EndoUltraTM 40 kHz frequency, it did not produce a substantial effect compared to the conventional ultrasonic range of 27 to 33 kHz. This was confirmed by the absence of the reduction of bacterial loads between the two techniques. Further research is needed to elucidate the contribution of cavitation to the efficacy of ultrasonic irrigation.

An unexpected result was that in spite of a different flow system, the EndoVac negative pressure device was not statistically different from both ultrasonic devices in terms of antimicrobial efficacy. In their study, Townsend (Townsend and Maki 2009) compared several agitation and irrigation devices in terms of antibacterial efficacy using E. faecalis. They found that ultrasonic agitation was significantly more effective than needle irrigation or EndoVac irrigation. The differences between results in the current study and the study conducted by Townsend may be explained by differences in the experiment design. The Townsend group irrigated with water instead of NaOCl and they used plastic canals instead of extracted teeth with dentinal tubules as in our study. Although using water may isolate the pure mechanical effect, NaOCl is used in practice and may yield a more realistic model of the synergistic effects of ultra-sonication and the irrigant (Cameron 1987). In addition, replenishment of spent solution may be an important dynamic factor in NaOCl reactions with organic tissue (Moorer and Wesselink 1982; Gulabivala et al. 2010) as opposed to water as an irrigant alone.

In this study, we observed that EndoVac significantly reduced the bacterial loads compared to the needle irrigation controls. This finding was in agreement with previous antibacterial studies (Hockett et al. 2008; Pawar et al. 2012; Cohenca et al. 2010) with limitations due to the differences in the study design.

Hockett et al. (Molander et al. 1998) found significantly better antibacterial efficacy with EndoVac negative pressure irrigation treatment compared to standard positive pressure needle irrigation in extracted mandibular molars with 6% NaOCl in 45/.02 and 35/.02 tapered canals. The present study differed in terms of NaOCl concentration (1%), canal shape (tapered 35/.04), and volume (3.0 ml total). Consistently refreshing with 1% NaOCl solution should suffice to dissolve the entire pulp tissue in the course of an endodontic treatment reducing the need for concentrated solutions with higher toxicity (Zehnder 2006; Moorer and Wesselink 1982).

A study conducted in patients that underwent endodontic treatment showed no difference in antimicrobial efficacy between EndoVac and standard needle irrigation with 0.5% NaOCl (Townsend and Maki 2009). The EndoVac manufacturer’s clinical protocol calls for the use of at least 5.25% NaOCl with one macro-cannula cycle (30 s) and 3 micro-cannula cycles (90 s each) for a total of 5 min of irrigant exposure. The time, concentration, and volume in our study were modified to allow for equal exposure of NaOCl between the device techniques.

There was no significant difference in bacterial load reduction between ultrasonic devices and the needle irrigation controls (EndoUltra vs 1% NaOCl control, p = 0.025; EndoUltra vs negative control, p = 0.018; conventional ultrasonic vs NaOCl control, p = 0.019; conventional ultrasonic vs negative control, p = 0.018). However, the p values were very close to significant. The small number of controls may possibly explain the discrepancy since there were only two negative controls with phosphate-buffered saline irrigant (Figs. 2 and 3).

Fig. 2
figure 2

Negative control. Upon completion of instrumentation, NaOCl was inactivated with 5% sodium thiosulfate for 5 min followed by irrigation with 5 mL of 17% EDTA for 1 min to ensure the complete removal of smear layer

Full size image
Fig. 3
figure 3

Positive control. Enterococcus faecalis (strain OG1RF) was cultured in 1 ml of brain-heart infusion (BHI) for 24 h and inoculated into 5 ml of fresh BHI with 2% glucose solution. The specimen root canals were inoculated with 100 μL of the suspension and incubated at 37° for 30 days with weekly medium change, ×15000

Full size image

We also discovered variability in the bacterial counts using the syringe irrigation method This observation may be explained by the inherent inconsistency in the manual syringe technique (Nielsen and Craig Baumgartner 2007). The advantage of the traditional side needle technique is the low cost and simplicity. In terms of disadvantages, manual operation of the positive pressure syringe may not be conducive due to inconsistent operator technique, potentially resulting in varying flow rate, pressure, and turbulence. In addition, a traditional needle has a side-facing vent, even when rotated may not consistently affect the sides of the canal evenly while projecting very limited turbulence (approximately 1.5 mm) and hydrodynamic shear stress to effect cleaning (Chen et al. 2014)

Some disadvantages posed by ultrasonic instrumentation include ledging (Boutsioukis and Tzimpoulas 2016) with loss of working length and instrument breakage (Pedrazzi et al. 2010). A disadvantage of the original EndoVac system is that it is relatively complicated to use in practice, requiring two hands or operators, one for introduction of irrigant with the delivery tip and one for cannula vacuum. Clogging of the very small micro-cannula vents if larger debris has not been removed adequately with larger macro-cannula vacuum efforts is another disadvantage of the EndoVac. However, this situation may be remedied with positive pressure flush or changing the cannula (Nielsen and Craig Baumgartner 2007). In spite of these disadvantages, the EndoVac may present an advantage in breaking vapor lock. Vapor lock occurs when a gas bubble remains entrapped in the apical portion of the root canal, precluding fluid entry flow (Gu et al. 2009). Acoustic micro-streaming and cavitation, the hydrodynamic phenomena of ultrasonic, cannot occur effectively in the absence of liquids, leading to vapor lock (Gu et al. 2009), which was not a judge factor during the present experiment. In a recent study by Parente et al. (Parente et al. 2010), they showed that a combination of needle syringe irrigation and the manual dynamic agitation method was less effective than the EndoVac in removing smear layer and debris from closed canal systems. The advantage of the ultrasonic devices is their simplicity of use, especially with the cordless EndoUltra handpiece, while the EndoVac has the benefit of rapid irrigant volume delivery with circulation (Nielsen and Craig Baumgartner 2007) and the tendency against extrusion (Parente et al. 2010).

Conclusion

Overall, the results of the present study showed no difference between the EndoVac negative pressure irrigation system, conventional ultrasonic, and portable EndoUltra systems.

While clinical decisions should be based on high-level evidence, for the irrigation techniques using root canal instrumentation, clinicians may choose to base their decisions upon the mechanical advantages of each system balanced against the practicality of use, cost, and on a case-by-case basis of necessity for the unique advantages of each technique. Future studies are needed on the combined effect of these devices.

Availability of data and materials

Please contact corresponding author for data request.

Abbreviations

CA:

California

CFU:

Colony forming units

E. faecalis :

Enterococcus faecalis

EDTA:

Ethylene diamine tetra-acetic acid

kHz:

Kilohertz

ml:

Milliliter

mm:

Millimeter

MO:

Missouri

N:

Number

NaOCl:

Sodium hypochlorite

NC:

North Carolina

NiTi:

Nickel titanium

NJ:

New Jersey

OK:

Oklahoma

PA:

Pennsylvania

PBS:

Phosphate-buffered solution

S1, S2:

Sample one, sample two

TX:

Texas

WI:

Wisconsin

μL:

Microliters

References

  • Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: an insight into the mechanisms involved. J Endod. 1987;13:93–101.

    Article  PubMed  Google Scholar 

  • Ahmad M, Pitt Ford TR, Crum LA. Ultrasonic debridement of root canals: acoustic streaming and its possible role. J Endod. 1987b;13:490–9.

    Article  PubMed  Google Scholar 

  • Ahmad M, Pitt Ford TR, Crum LA, Walton AJ. Ultrasonic debridement of root canals: acoustic cavitation and its relevance. J Endod. 1988;14:486–93.

    Article  PubMed  Google Scholar 

  • Al-Ahmad A, Ameen H, Pelz K, Karygianni L, Wittmer A, Anderson AC, et al. Antibiotic resistance and capacity for biofilm formation of different bacteria isolated from endodontic infections associated with root-filled teeth. J Endod. 2014;40:223–30.

    Article  PubMed  Google Scholar 

  • Barbosa-Ribeiro M, De-Jesus-Soares A, Zaia AA, Ferraz CCR, Almeida JFA, Gomes BPFA. Quantification of lipoteichoic acid contents and cultivable bacteria at the different phases of the endodontic retreatment. J Endod. 2016;42:552–6.

    Article  PubMed  Google Scholar 

  • Basrani B, Haapasalo M. Update on endodontic irrigating solutions. Endod Topics. 2012;27:74–102.

    Article  Google Scholar 

  • Boutsioukis C, Tzimpoulas N. Uncontrolled removal of dentin during in vitro ultrasonic irrigant activation. J Endod. 2016;42:289–93.

    Article  PubMed  Google Scholar 

  • Cameron JA. The synergistic relationship between ultrasound and sodium hypochlorite: a scanning electron microscope evaluation. J Endod. 1987;13:541–5.

    Article  PubMed  Google Scholar 

  • Chen JE, Nurbakhsh B, Layton G, Bussmann M, Kishen A. Irrigation dynamics associated with positive pressure, apical negative pressure and passive ultrasonic irrigations: a computational fluid dynamics analysis. Aust Endod J. 2014;40:54–60.

    Article  PubMed  Google Scholar 

  • Chrepa V, Kotsakis GA, Pagonis TC, Hargreaves KM. The effect of photodynamic therapy in root canal disinfection: a systematic review. J Endod. 2014;40:891–8.

    Article  PubMed  Google Scholar 

  • Cohenca N, Heilborn C, Johnson JD, Flores DSH, Ito IY, da Silva LAB. Apical negative pressure irrigation versus conventional irrigation plus triantibiotic intracanal dressing on root canal disinfection in dog teeth. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2010;109:e42–6.

    Article  Google Scholar 

  • Dahlen G, Linde A, Moller AJR, Ohman A. A retrospective study of microbiological samples from oral muchosal lesions. Oral Surg Oral Med Oral Pathiol. 1982;53:250–5.

    Article  Google Scholar 

  • Dalton BC, Orstavik D, Phillips C, Pettiette M, Trope M. Bacterial reduction with nickel-titanium rotary instrumentation. J Endod. 1998;24:763–7.

    Article  PubMed  Google Scholar 

  • Duggan JM, Sedgley CM. Biofilm formation of oral and endodontic Enterococcus faecalis. J Endod. 2007;33:815–8.

    Article  PubMed  Google Scholar 

  • Evans M, Davies JK, Sundqvist G, Figdor D. Mechanisms involved in the resistance of Enterococcus faecalis to calcium hydroxide. Int Endod J. 2002;35:221–8.

    Article  PubMed  Google Scholar 

  • Gu L-S, Kim JR, Ling J, Choi KK, Pashley DH, Tay FR. Review of contemporary irrigant agitation techniques and devices. J Endod. 2009;35:791–804.

    Article  PubMed  Google Scholar 

  • Guivarc'h M, Ordioni U, Ahmed HMA, Cohen S, Catherine J-H, Bukiet F. Sodium hypochlorite accident: a systematic review. J Endod. 2017;43:16–24.

    Article  PubMed  Google Scholar 

  • Gulabivala K, Ng YL, Gilbertson M, Eames I. The fluid mechanics of root canal irrigation. Physiol Measur. 2010;31:R49–84.

    Article  Google Scholar 

  • Hockett JL, Dommisch JK, Johnson JD, Cohenca N. Antimicrobial efficacy of two irrigation techniques in tapered and nontapered canal preparations: an in vitro study. J Endod. 2008;34:1374–7.

    Article  PubMed  Google Scholar 

  • Hubscher W, Barbakow F, Peters OA. Root-canal preparation with FlexMaster: canal shapes analysed by micro-computed tomography. Int Endod J. 2003;36:740–7.

    Article  PubMed  Google Scholar 

  • Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposures of dental pulps in germ-free and conventional laboratory rats. Oral Surg Oral Med Oral Pathol. 1965;20:340–9.

    Article  PubMed  Google Scholar 

  • Kleier DJ, Averbach RE, Mehdipour O. The sodium hypochlorite accident: experience of diplomates of the American Board of Endodontics. J Endod. 2008;34:1346–50.

    Article  PubMed  Google Scholar 

  • Lloyd A, Navarette G, Marchesan MA, Clement D. Removal of calcium hydroxide from Weine Type II systems using photon-induced photoacoustic streaming, passive ultrasonic, and needle irrigation: a microcomputed tomography study. J Appl Oral Sci. 2016;24:543–8.

    Article  PubMed  PubMed Central  Google Scholar 

  • Macedo R, Verhaagen B, Rivas DF, Versluis M, Wesselink P, van der Sluis L. Cavitation measurement during sonic and ultrasonic activated irrigation. J Endod. 2014;40:580–3.

    Article  PubMed  Google Scholar 

  • Mohammadi Z. Sodium hypochlorite in endodontics: an update review. Int Dental J. 2008;58:329–41.

    Article  Google Scholar 

  • Molander A, Reit C, Dahlen G, Kvist T. Microbiological status of root-filled teeth with apical periodontitis. Int Endod J. 1998;31:1–7.

    Article  PubMed  Google Scholar 

  • Moorer WR, Wesselink PR. Factors promoting the tissue dissolving capability of sodium hypochlorite. Int Endod J. 1982;15:187–96.

    Article  PubMed  Google Scholar 

  • Nielsen BA, Craig Baumgartner J. Comparison of the EndoVac system to needle irrigation of root canals. J Endod. 2007;33:611–5.

    Article  PubMed  Google Scholar 

  • Ordinola-Zapata R, Bramante CM, Aprecio RM, Handysides R, Jaramillo DE. Biofilm removal by 6% sodium hypochlorite activated by different irrigation techniques. Int Endod J. 2014;47:659–66.

    Article  PubMed  Google Scholar 

  • Paque F, Balmer M, Attin T, Peters OA. Preparation of oval-shaped root canals in mandibular molars using nickel-titanium rotary instruments: a micro-computed tomography study. J Endod. 2010;36:703–7.

    Article  PubMed  Google Scholar 

  • Parente JM, Loushine RJ, Susin L, Gu L, Looney SW, Weller RN, et al. Root canal debridement using manual dynamic agitation or the EndoVac for final irrigation in a closed system and an open system. Int Endod J. 2010;43:1001–12.

    Article  PubMed  Google Scholar 

  • Park E. Ultrasonics in endodontics. Endod Topics. 2013;29:125–59.

    Article  Google Scholar 

  • Park E, Shen Y, Haapasalo M. Irrigation of the apical root canal. Endod Top. 2012;27:54–73.

    Article  Google Scholar 

  • Pawar R, Alqaied A, Safavi K, Boyko J, Kaufman B. Influence of an apical negative pressure irrigation system on bacterial elimination during endodontic therapy: a prospective randomized clinical study. J Endod. 2012;38:1177–81.

    Article  PubMed  Google Scholar 

  • Pedrazzi V, de Oliveira-Neto JM, Sequeira P, Fedorowicz Z, Nasser M. Hand and ultrasonic instrumentation for orthograde root canal treatment of permanent teeth. J Appl Oral Sci. 2010;18:268–72.

    Article  PubMed  PubMed Central  Google Scholar 

  • Peters OA. Current challenges and concepts in the preparation of root canal systems: a review. J Endod. 2004;30:559–67.

    Article  PubMed  Google Scholar 

  • Plotino G, Pameijer CH, Maria Grande N, Somma F. Ultrasonics in endodontics: a review of the literature. J Endod. 2007;33:81–95.

    Article  PubMed  Google Scholar 

  • Portenier I, Waltimo TMT, Haapasalo M. Enterococcus faecalis–the root canal survivor and ‘star’ in post-treatment disease. Endod Top. 2003;6:135–59.

    Article  Google Scholar 

  • Ricucci D, Siqueira JF Jr. Biofilms and apical periodontitis: study of prevalence and association with clinical and histopathologic findings. J Endod. 2010;36(8):1277–88.

    Article  PubMed  Google Scholar 

  • Rosen E, Tsesis I, Elbahary S, Storzi N, Kolodkin-Gal I. Eradication of Enterococcus faecalis Biofilms on Human Dentin. Front Microbiol. 2016;7:1–9.

    Article  Google Scholar 

  • Shen Y, Gao Y, Lin J, Ma J, Wang Z, Haapasalo M. Methods and models to study irrigation. Endod Topics. 2012;27:3–34.

    Article  Google Scholar 

  • Siqueira JF Jr. Aetiology of root canal treatment failure: why well-treated teeth can fail. Int Endod J. 2001;34:1–10.

    Article  PubMed  Google Scholar 

  • Siqueira JF Jr, Rocas IN. Clinical implications and microbiology of bacterial persistence after treatment procedures. J Endod. 2008;34(1291-1301):e1293.

    Google Scholar 

  • Spoleti P, Siragusa M, Spoleti MJ. Bacteriological evaluation of passive ultrasonic activation. J Endod. 2003;29:12–4.

    Article  PubMed  Google Scholar 

  • Stuart CH, Schwartz SA, Beeson TJ, Owatz CB. Enterococcus faecalis: its role in root canal treatment failure and current concepts in retreatment. J Endod. 2006;32:93–8.

    Article  PubMed  Google Scholar 

  • Tay FR, Gu LS, Schoeffel GJ, Wimmer C, Susin L, Zhang K, Arun SN, Kim J, Looney SW, Pashley DH. Effect of vapor lock on the root canal debridement by using a side-vented needle for positive-pressure irrigant delivery. J Endod. 2010;36:745–50.

    Article  PubMed  PubMed Central  Google Scholar 

  • Townsend C, Maki J. An in vitro comparison of new irrigation and agitation techniques to ultrasonic agitation in removing bacteria from a simulated root canal. J Endod. 2009;35:1040–3.

    Article  PubMed  Google Scholar 

  • Wu M-K, R'Oris A, Barkis D, Wesselink PR. Prevalence and extent of long oval canals in the apical third. Oral Surg Oral Med Oral Pathol Oral Radiol Endodontol. 2000;89:739–43.

    Article  Google Scholar 

  • Zehnder M. Root canal irrigants. J Endod. 2006;32:389–98.

    Article  PubMed  Google Scholar 

Download references

Acknowledgements

Special thanks to Julian Holland III for performing the statistical work of the study.

Funding

Study supported by corresponding author’s research funds 0012625.

Author information

Authors and Affiliations

  1. Department of Endodontics, University of Texas Health Science Center at Houston SOD, 7500 Cambridge St. Suite 6417, Houston, TX, 77054, USA

    Randall Mikulik & David E. Jaramillo

  2. Department of Diagnostic and Biomedical Sciences, University of Texas Health Science Center at Houston SOD, Houston, USA

    Ali Naji & Ransome van der Hoeven

  3. Department of Endodontology, the Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Tel Aviv, Israel

    Igor Tsesis & Eyal Rosen

Authors
  1. Randall Mikulik
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Ali Naji
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Ransome van der Hoeven
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Igor Tsesis
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Eyal Rosen
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. David E. Jaramillo
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

RM was in charge of collecting and preparing teeth, helped in laboratory work and data collection, reviewed the literature. AN and RvdH were responsible for microbiology lab; helped in the preparation of broth, cultivation of bacteria, and BHI plates; performed the CFU’s counting; and reviewed the manuscript. IT and ER helped in the manuscript preparation and final reviews. DEJ designed the study, mentored Dr. Mikulik, made laboratory work, and plating of samples and helped in data collection, DEJ performed SEM imaging and final review of the manuscript. All authors read and approved the final manuscript.

Corresponding author

Correspondence to David E. Jaramillo.

Ethics declarations

Ethics approval and consent to participate

The following study received approval (HSC-DB-16-0871) qualified for exempt status according to 45 CFR 46.101(b) (waiver of consent granted) from the Committee for the protection of human subjects of the University of Texas Health Science Center at Houston Institutional Review Board (IRB) office.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interest.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Mikulik, R., Naji, A., van der Hoeven, R. et al. Efficacy evaluation of a cordless ultrasonic unit in achieving reduction of bacterial load within a root canal system as compared to a conventional ultrasonic unit and negative pressure irrigation. Evid.-based endod 4, 2 (2019). https://doi.org/10.1186/s41121-019-0019-z

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s41121-019-0019-z

Keywords