ORIGINAL RESEARCH

https://doi.org/10.5005/jp-journals-10005-2885
International Journal of Clinical Pediatric Dentistry
Volume 17 | Issue 6 | Year 2024

In Vitro Efficacy of Apical Negative Pressure Irrigation in Primary Teeth: A Smear Layer Analysis

Sheetal D Badnaware¹ https://orcid.org/0000-0003-3678-5914, Adesh Kakade² https://orcid.org/0000-0002-0363-7731, Vilas Takate³ https://orcid.org/0009-0003-1816-920X, Akanksha Juneja⁴ https://orcid.org/0000-0003-4127-1133, Heeresh Shetty⁵ https://orcid.org/0000-0002-5487-4083, Anitha Santosh⁶ https://orcid.org/0000-0002-9593-9488, Mahesh R Khairnar⁷ https://orcid.org/0000-0003-4274-9565

¹Unit of Pediatric and Preventive Dentistry, Faculty of Dental Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

²Department of Pediatric and Preventive Dentistry, Nair Hospital Dental College, Mumbai, Maharashtra, India

³Department of Pediatric and Preventive Dentistry, Government Dental College and Hospital, Mumbai, Maharashtra, India

⁴Department of Pediatric and Preventive Dentistry, Jamia Millia Islamia, New Delhi, India

⁵Department of Conservative Dentistry, Nair Hospital Dental College, Mumbai, Maharashtra, India

⁶Private Practice, Austin, Texas, United States

⁷Unit of Public Health Dentistry, Faculty of Dental Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India

Corresponding Author: Adesh Kakade, Department of Pediatric and Preventive Dentistry, Nair Hospital Dental College, Mumbai, Maharashtra, India, Phone: +91 9821289144, e-mail: adeshkakade@rediffmail.com

ABSTRACT

Aim and background: This study aimed to assess the efficacy of root canal debris removal in primary teeth through irrigation using the Endo-Irrigator Plus (CWAIS).

Materials and methods: A total of 25 primary mandibular first molars were divided into five groups, with five teeth in each group. After determining the working length and performing biomechanical preparation, groups I and II were subjected to hand and rotary instrumentation (ProTaper, Dentsply, United States of America) with conventional syringe irrigation with positive pressure, while groups III and IV were instrumented using hand and rotary instrumentation with positive and negative pressure irrigation employing the Endo-Irrigator Plus (CWAIS) system. Sodium hypochlorite (5.25%) and ethylenediaminetetraacetic acid (EDTA) (17%) were used as irrigants. Group V served as the control group, undergoing only root canal access opening. The removal of the smear layer was analyzed at the cervical, middle, and apical thirds of the canal using environmental scanning electron microscopy (SEM). Statistical significance was set at p < 0.05.

Results: Statistically significant differences were observed among all groups at the cervical, middle, and apical levels (p < 0.05). Groups III and IV exhibited significantly lower smear scores at all levels, particularly in the apical third, as observed through SEM examination.

Conclusion: The use of the Endo-Irrigator Plus (CWAIS) system demonstrated superior debridement of intracanal debris in primary teeth compared to the positive pressure irrigation method.

How to cite this article: Badnaware SD, Kakade A, Takate V, et al. In Vitro Efficacy of Apical Negative Pressure Irrigation in Primary Teeth: A Smear Layer Analysis. Int J Clin Pediatr Dent 2024;17(6):653-657.

Source of support: Nil

Conflict of interest: None

Keywords: Apical negative pressure irrigation, Endo-Irrigator Plus (CWAIS), Smear layer.

INTRODUCTION

The success of endodontic treatment relies on effective instrumentation, disinfection, and obturation of the root canal system. While considerable research has been conducted on disinfection methods, achieving effective disinfection in primary teeth, especially in the apical region, remains a significant challenge for clinicians. This challenge arises due to factors such as physiological resorption, inherent limitations in canal preparation (e.g., widely divergent, curved, and fragile primary root canal morphology), and the continuous deposition of secondary dentin in children aged 4–5 years.¹^-⁵

The conventional needle irrigation method, which utilizes positive pressure, is commonly employed by clinicians. However, studies have indicated that even after chemomechanical preparation, certain areas of the root canal system remain uncleaned.⁶^,⁷ It has also been demonstrated that the conventional needle irrigation method is less effective in cleaning the apical areas of the canal compared to the coronal areas.⁸^,⁹

Various irrigation systems have been developed and introduced to address the challenges associated with root canal disinfection. One such innovative system is the Endo-Irrigator Plus, which operates on the principle of continuous warm-activated irrigation and evacuation (CWAIS). This advanced device is equipped with a built-in suction and heater, as well as positive and negative tips designed to deliver warm sodium hypochlorite into the root canal system via single-use 28–30-gauge side-vented needles. A notable advantage of this system is its ability to maintain a continuous flow of warm irrigant throughout the root canal procedure.

Despite the potential benefits offered by the Endo-Irrigator Plus, there remains a paucity of scientific investigations into the efficacy of smear removal using the apical negative pressure irrigation method employed by this device.

Consequently, the objective of the present study was to assess the debridement efficacy of the Endo-Irrigator Plus, which combines positive and apical negative pressure irrigation systems, in the root canal treatment of primary teeth.

MATERIALS AND METHODS

The protocol for this study was approved by the Research Ethics Committee of the University (DCGI reg. no.—ECR/569/Inst/MH/2014). The study was conducted in the Department of Pediatric and Preventive Dentistry. A total of 25 extracted primary mandibular first molars were selected based on inclusion criteria. Teeth were extracted due to clinical nonrestorability or based on the preference of parents or guardians. Radiographs were taken to assess internal resorption and furcation involvement. The external surfaces of the teeth were debrided with a hand scaler. The mesiobuccal root of each primary mandibular molar was selected and stored in a formalin solution with a preservative. The samples were then divided into five experimental groups (N = 25) based on the irrigation techniques and biomechanical preparation methods.

Group I (n = 5): Hand instrumentation with conventional syringe irrigation.
Group II (n = 5): Rotary instrumentation with conventional syringe irrigation.
Group III (n = 5): Hand instrumentation with Endo-Irrigator Plus device.
Group IV (n = 5): Rotary instrumentation with Endo-Irrigator Plus device.
Group V (n = 5): Control group, root canal access opening only, no irrigation performed.

The crowns of the teeth were removed using a carborundum disk, and the roots were split with a chisel and mallet. The experimental procedures for groups I and II were based on the protocols provided by Nielsen and Baumgartner et al.¹⁰

Root Canal Preparation Procedures

Standard endodontic access cavity preparation was performed using a small round bur (Mani Inc., Japan) for all groups. Canal patency was checked using a #10 K-file (Mani Inc., Japan) with a length of 21 mm. The apex of the root was closed with sticky wax to create a closed system in the root canal and prevent irrigant extrusion. Biomechanical preparation was carried out using a new set of files for each tooth.

For Group I

Biomechanical preparation was performed using hand files up to a #35 K-file with a length of 21 mm.

For Group II

Biomechanical preparation was performed using rotary ProTaper files (Dentsply) up to the F1 file, with an Endo motor rotary handpiece (Dentsply torque 4.5 Ncm, level 4) and a length of 21 mm. The rotary file sequence followed was SX, S1, S2, and F1, employing the crown-down technique up to 0.5 mm short of the anatomical apex. Recapitulation was performed after each file usage. Irrigation duration was consistent for all samples in both groups, with 1 mL of 5.25% sodium hypochlorite being delivered using a 27-gauge side-vented closed-ended needle (NaviTip) and syringe. Between cleaning and shaping, each sample was irrigated with 1 mL of 5.25% sodium hypochlorite for 1 minute. This was followed by irrigation with 1 mL of 17% ethylenediaminetetraacetic acid (EDTA) (RC HELP prime dental product) solution for 1 minute, and finally, 1 mL of 5.25% sodium hypochlorite for 1 minute. Canals were dried with absorbent paper points, and final irrigation with 1 mL of normal saline was performed to prevent an acid–base reaction.

For Groups III and IV

Endodontic preparation was similar to groups I and II for groups III and IV, respectively. Irrigation was performed using the Endo-Irrigator Plus (CWAIS). The manufacturer’s instructions were followed for irrigation. Warm sodium hypochlorite, heated to 50°C, was used with positive pressure tips, delivering the irrigant up to the middle third of the canal during instrumentation for 1 minute, while simultaneously evacuating the irrigant. Frequent irrigation was performed in all samples during biomechanical preparation with 1 mL of 5.25% sodium hypochlorite for 1 minute. This was followed by irrigation with 1 mL of 17% EDTA (RC HELP prime dental product) solution for 1 minute and another irrigation with 1 mL of 5.25% sodium hypochlorite for 1 minute. The same irrigation protocol was used for the apical third of the canal, using negative pressure tips placed 1 mm short of the apex of the root. Final irrigation with 1 mL of normal saline was performed after the last instrument to prevent an acid-base reaction.

Group V

For the control group, only root canal access opening was performed, and no instrumentation or irrigation was conducted. Smear layer removal was evaluated using environmental scanning electron microscopy (SEM).

Environmental Scanning Electron Microscopy

The samples used for the environmental SEM study were longitudinally grooved into buccal and lingual halves, which were split using a chisel and mallet. The most visible parts of the canals were selected and divided into three main sections—cervical third, middle third, and apical third. The samples were air-dried and evaluated using environmental SEM. Two areas of each third were selected, and images were captured at 5000× magnification to assess smear layer removal. The SEM photographs were independently assessed by two blinded examiners. The cleanliness of the images was evaluated and scored at the cervical, middle, and apical areas of each sample according to the criteria given by Hulsmann et al. ¹¹

RESULTS

The data obtained from the study were analyzed using analysis of variance (ANOVA) to determine the significance of the study parameters among the different groups. If the ANOVA values were found to be significant, post hoc analysis was performed. IBM Statistical Package for the Social Sciences (SPSS) Statistics 20.0 software (IBM Corporation, Armonk, New York, United States of America) was used for the data analysis.

Figures 1A to C depict the mean smear layer removal scores with standard deviation for all five groups at three different levels—cervical third, middle third, and apical third were analyzed by the ANOVA test. Statistically significant differences were observed between all groups at all three levels (p < 0.05). Tukey’s multiple post hoc analysis revealed highly significant differences among the groups. Environmental SEM analysis demonstrated that group I (Figs 2A to C) had significantly higher smear layer scores compared to group II (Figs 2D to F). The smear layer scores for group I at the cervical third, middle third, and apical third of the root canal were 4, 2, and 1, respectively, which were higher than those for group II, which were 1, 1, and 2, respectively. A higher smear layer score indicates a greater presence of the smear layer and closer dentinal tubules.

Figs 1A to C: Graphical presentation of comparison of smear layer score at the (A) cervical third; (B) middle third; (C) apical third of root canal levels among different groups using ANOVA test. The scores are presented as mean (standard deviation)

Figs 2A to O: Scanning electronic microscopic (SEM) images illustrating the removal of smear layer in different groups. (A to C) Group I: hand instrumentation with conventional syringe irrigation; (D to F) Group II: rotary instrumentation with conventional syringe irrigation; (G to I) Group III: hand instrumentation with Endo-irrigator Plus device; (J to L) Group IV: rotary instrumentation with Endo-irrigator Plus device; (M to O) Group V: control group. The images depict the cervical third, middle third, and apical third of the root canal at a magnification 5000×

Furthermore, group III exhibited significantly higher smear scores compared to group IV at all levels. The smear layer scores for group III at the cervical third, middle third, and apical third of the canal were 3, 2, and 1, respectively (Figs 2G to I), while for group IV, they were 1, 1, and 1 at the respective locations (Figs 2J to L).

In contrast, the control group showed the highest smear score compared to all other groups, with a score of 5 at the cervical third, middle third, and apical third of the canal (Figs 2M to O).

DISCUSSION

The importance of infection control cannot be overstated in the success of endodontic therapy. One of the challenges in achieving effective instrumentation lies in the apical part of the root canal system, which is often difficult to reach due to its widely divergent, curved, and fragile morphology. Conventional syringe irrigation systems, commonly employed in endodontics, have a significant drawback. They tend to lose a certain amount of irrigant before it reaches the apical region, resulting in a gradual decrease in the amount of cleaning solution that comes into contact with the canal wall.¹²

To overcome this limitation, newer irrigation methods based on negative pressure technology, such as Endo-Irrigator Plus (CWAIS) and EndoVac, as well as ultrasonic devices like passive ultrasonic irrigation (PUI), have been introduced in endodontics. One advantage of using apical negative pressure irrigation is that it breaks the vapor lock effect created by irrigating solutions, allowing them to reach the full working length. In our study, we utilized the Endo-Irrigator Plus system, which combines both positive and negative pressure irrigation, unlike other systems that only offer negative pressure irrigation tips. Our findings demonstrated that the Endo-Irrigator Plus (CWAIS) achieved better removal of the smear layer in the apical portion of the root canal system compared to conventional syringe irrigation. Similar results were observed by Srivastava et al. in their study comparing conventional syringe irrigation with positive pressure and Endo-Irrigator Plus (CWAIS).¹³ Other authors have also reported similar results, showing less extrusion of sodium hypochlorite when using Endo-Irrigator Plus (CWAIS) compared to conventional pressure irrigation.¹⁴^,¹⁵

In our study, we delivered irrigants into the canal at a rate of 1 mL/minute for conventional syringe irrigation with positive pressure. However, we did not measure the rate of irrigants reaching the canal for Endo-Irrigator Plus since the volume of irrigants reaching the canal is independent of the number of irrigants delivered from the syringe. As an adjunct irrigating solution, we used EDTA, which demineralizes the dentin’s inorganic structure, facilitating the cleaning of narrow canals. The chelating effect with calcium ions enhances the effectiveness of sodium hypochlorite, especially when preheated at higher concentrations.¹⁶^,¹⁷

Recent studies have shown that the Endo-Irrigator Plus (CWAIS) resulted in significantly less debris or pulp tissue in the root canals of permanent teeth.¹⁸^,¹⁹ Similar results were reported by Nielsen and Baumgartner and Siu and Baumgartner on vital premolar teeth.¹⁰^,²⁰ Nevertheless, in our study, neither delivery system was able to completely remove debris from the root canals. However, better removal of the smear layer and more open dentinal tubules were observed when using Endo-Irrigator Plus (CWAIS) with both positive and negative pressure irrigation systems compared to conventional syringe irrigation with positive pressure, particularly in the apical third of primary teeth root canals.

The use of rotary instrumentation with positive and negative pressure systems, such as Endo-Irrigator Plus (CWAIS), proved to be effective in removing a significant amount of smear layer in all sections of primary teeth root canals. In contrast, the control group, where only root canal access opening was performed without irrigation, exhibited an abundant amount of smear layer and blocked dentinal tubules. To be clinically relevant, in vitro studies should aim to reproduce the clinical situation as closely as possible. When investigating the effect of irrigation dynamics, researchers should consider the presence of periradicular tissues surrounding the root surface and the closed canal system.

Our results are consistent with previous studies demonstrating that apical pressure aids in better cleaning of the apical third of the root canal. Within the limitations of our study, the Endo-Irrigator Plus (CWAIS) demonstrated superior results in smear layer removal compared to conventional syringe irrigation.

CONCLUSION

Within the parameters of our current study, the utilization of the Endo-Irrigator Plus (CWAIS) system for irrigation exhibited superior removal of the smear layer in the root canals of primary teeth. The incorporation of apical negative pressure irrigation in the CWAIS system potentially enhances the dissolving capacity of irrigating solutions, extends their exposure time, and promotes better contact with the root canal walls, particularly in uninstrumented areas of the root canal system. Further investigation is warranted to assess the efficacy of warm sodium hypochlorite with continuous irrigation in primary teeth.

Clinical Significance

The findings of this study contribute to our understanding of the significance of the apical negative irrigation method in the pulp therapy of primary teeth. The implementation of this method is expected to have a positive impact on the outcomes of root canal treatment, primarily attributed to its effectiveness in removing the smear layer.

ORCID

Sheetal D Badnaware https://orcid.org/0000-0003-3678-5914

Adesh Kakade https://orcid.org/0000-0002-0363-7731

Vilas Takate https://orcid.org/0009-0003-1816-920X

Akanksha Juneja https://orcid.org/0000-0003-4127-1133

Heeresh Shetty https://orcid.org/0000-0002-5487-4083

Anitha Santosh https://orcid.org/0000-0002-9593-9488

Mahesh R Khairnar https://orcid.org/0000-0003-4274-9565

REFERENCES

1. Haapasalo M, Shen Y, Qian W, et al. Irrigation in endodontics. Dent Clin 2010;54(2):291–312. DOI: 10.1016/j.cden.2009.12.001

2. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four root canal irrigation regimens. J Endod 1987;13(4):147–157. DOI: 10.1016/s0099-2399(87)80132-2

3. Ahmed HM. Anatomical challenges, electronic working length determination and current developments in root canal preparation of primary molar teeth. Int Endod J 2013;46(11):1011–1022. DOI: 10.1111/iej.12134

4. Goerig AC, Camp JH. Root canal treatment in primary teeth: a review. Pediatr Dent 1983;5(1):33–37.

5. Coll JA, Josell S, Casper JS. Evaluation of a one-appointment formocresol pulpectomy technique for primary molars. Pediatr Dent 1985;7(2):123–129.

6. Lin LM, Pascon EA, Skribner J, et al. Clinical, radiographic, and histologic study of endodontic treatment failures. Oral Surg Oral Med Oral Pathol 1991;71(5):603–611. DOI: 10.1016/0030-4220(91)90371-i

7. Siqueira JF, Araújo MC, Garcia PF, et al. Histological evaluation of the effectiveness of five instrumentation techniques for cleaning the apical third of root canals. J Endod 1997;23(8):499–492. DOI: 10.1016/S0099-2399(97)80309-3

8. Chow TW. Mechanical effectiveness of root canal irrigation. J Endod 1983;9(11):475–479. DOI: 10.1016/S0099-2399(83)80162-9

9. Boutsioukis C, Lambrianidis T, Kastrinakis E. Irrignat flow within a prepared root canal using various flow rates: a computational fluid dynamics study. Int Endod J 2009;42(2):144–155. DOI: 10.1111/j.1365-2591.2008.01503.x

10. Nielsen BA, Baumgartner JC. Comparison of the EndoVac system to needle irrigation of root canals. J Endod 2007;33(5):611–615.

11. Hulsmann M, Rümmelin C, Schäfers F. Root canal cleanliness after preparation with different endodontic handpieces and hand instruments: a comparative SEM investigation. J Endod 1997;23(5):301–306. DOI: 10.1016/S0099-2399(97)80410-4

12. Iriboz E, Bayraktar K, Turkaydin D, et al. Comparison of the efficacies of debris removal with four different irrigation techniques. J Curr Surg 2014;4(3):70–75. DOI: 10.14740/jcs242e

13. Srivastava I, Srivastava S, Grover R, et al. Comparative evaluation of efficacy of different irrigating needles and devices in removal of debris from apical third of root canal: an in vitro SEM study. Contemp Clin Dent 2021;12(3):222–229. DOI: 10.4103/ccd.ccd_468_20

14. Albrecht LJ, Baumgartner JC, Marshall JG. Evaluation of apical debris removal using various sizes and tapers of ProFile GT files. J Endod 2004;30(6):425–428. DOI: 10.1097/00004770-200406000-00012

15. Mandhotra P, Rai K, Grewal GS, et al. A comparative assessment of three different irrigating systems in root canal treatment: an in vitro study. J Pharm Bioallied Sci 2021;13(Suppl 1):S429–S431. DOI: 10.4103/jpbs.JPBS_587_20

16. Sirtes G, Waltimo T, Schaetzle M, et al. The effects of temperature on sodium hypochlorite short-term stability, pulp dissolution capacity, and antimicrobial efficacy. J Endod 2005;31(9):669–671. DOI: 10.1097/01.don.0000153846.62144.d2

17. Cunningham WT, Balekjian AY. Effect of temperature on collagen-dissolving ability of sodium hypochlorite endodontic irrigant. Oral Surg Oral Med Oral Pathol 1980;49(2):175–177. DOI: 10.1016/0030-4220(80)90313-8

18. Neelakantan P, Devaraj S, Jagannathan N. Histologic assessment of debridement of the root canal isthmus of mandibular molars by irrigant activation techniques ex vivo. J Endod 2016;42(8):1268–1272. DOI: 10.1016/j.joen.2016.05.005

19. Shetty VP, Naik BD, Pachlag AK, et al. Comparative evaluation of the amount of debris extruded apically using conventional syringe, passive ultrasonic irrigation and EndoIrrigator plus system: an in vitro study. J Conservat Dent 2017;20(6):411–414. DOI: 10.4103/JCD.JCD_200_17

20. Siu C, Baumgartner JC. Comparison of the debridement efficacy of the EndoVac irrigation system and conventional needle root canal irrigation in vivo. J Endod 2010;36(11):1782–1785. DOI: 10.1016/j.joen.2010.08.023

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