Abstract
Objective:
This study compared the potential for apical extrusion of sodium hypochlorite (NaOCl) when using needle irrigation (NI), passive ultrasonic irrigation (PUI), passive subsonic irrigation (PSI), and negative pressure system (NP).
Materials and Methods:
One hundred freshly extracted human permanent anterior teeth with complete root formation were embedded rigidly in agarose gel-containing cresol purple. Teeth were randomly allocated to six groups: G1-NI; G2-PUI; G3-PSI; G4-NP; G5-positive control; and G6-negative control. The chemomechanical preparation was completed and 12 ml of 3% NaOCl was delivered for 180 s in all groups. Dye diffusion was standardized by doing gel photography after the NaOCl final irrigation the Chi-square test and Kruskal–Wallis one-way analysis of variance test were used for the data analysis.
Results:
G1 had statistically significant apical extrusion compared to G2 (P = 0.001), G3 (P = 0.001), and G4 (P = 0.001) groups. G4 showed the least amount of apical extrusion.
Conclusions:
pH-sensitive gel model is useful in evaluating NaOCl extrusion. NP produced least NaOCl extrusion as compared to the other three systems. Due consideration should be given to the potential for apical extrusion of the irrigant before the selection of an irrigation system.
Keywords: Apical extrusion, EndoActivator, EndoVac, passive ultrasonic irrigation, sodium hypochlorite
INTRODUCTION
The success of root canal treatment depends on the meticulous cleaning and shaping of the root canal system.[1] The eradication of microorganisms from the root canal is the main goal of chemomechanical preparation.[2] Irrigation is the key to cleaning and disinfecting the areas where the instrument cannot reach.[3] Several studies have proven the effectiveness of sodium hypochlorite (NaOCl) for bacterial reduction and tissue dissolution.[4,5] However, inadvertent use of NaOCl poses a risk of its extrusion into the periapical region leading to pain, swelling, and tissue damage.[6,7] The effectiveness of an irrigation regimen depends on the working mechanisms of the irrigant.[8] In conventional needle irrigation (NI) system, a 27-G or 30-G needle is used just short of the apex. However, the predictable delivery of irrigants to the working length (WL) is often questionable with this technique due to the varied size and morphology of each canal. Moreover, little or no control over the pressure during syringe irrigation will lead to either incomplete debridement or forcing the irrigant past the apex.[9,10] Hence, several new irrigant delivery and activation systems such as passive ultrasonic irrigation (PUI), passive subsonic irrigation (PSI), and apical negative pressure system (NP) have been developed to overcome the abovementioned limitations. Safe delivery of irrigants to WL with minimal extrusion periapically is possible with NP (EndoVac, Discus Dental, Culver City, CA).[11] A delivery/evacuation tip simultaneously irrigates and evacuates irrigant from the pulp chamber, respectively. In PSI (EndoActivator, Dentsply Tulsa Dental Specialties, Tulsa, OK) system, the irrigant is agitated using sonic energy created by a handpiece and polymer tips of different sizes. In PUI, a noncutting and noncontacting U file is activated ultrasonically to increase the effectiveness of irrigation.
Previous studies testing apical extrusion did not evaluate the possible effect on periapical tissues because their methods extruded irrigants into vials of air.[12-15] The absence of tissue simulation in ex vivo experiments may significantly overestimate irrigant extrusion.[16] This study used a modified closed system agarose gel model to simulate tissue and to visibly capture and assess the extent of apical extrusion.[17]
Hence, this in vitro study was carried out to compare the potential for apical extrusion of NaOCl when using conventional 27-G NI, PUI, PSI, and NP systems.
MATERIALS AND METHODS
This in vitro study was carried out in the department of conservative dentistry and endodontics after obtaining institutional ethical clearance (9/12/70/XX/IEC/2020/X).
Tooth selection and instrumentation
A total of 120 freshly extracted human permanent anterior teeth with complete root formation were selected. Teeth with caries, cracks, restorations, and immature or resorbed roots were excluded (n = 20). After extraction, the teeth were washed under running tap water, cleaned of any attached tissue, and stored in the phosphate-buffered saline solution until use following the OSHA guidelines. A conventional lingual access cavity was prepared with a size #2 round bur. The flat incisal surface was made as a reference on the incisal edge for determining the WL. WL was determined by reducing 0.5 mm from the measurement at which a size #15K file was just visible directly at the root end under magnification (×2.5). Three readings were taken by two trained endodontists independently, and then, the average of the two values was considered as the final WL.
Tooth embedding
The teeth were embedded rigidly in an 0.2% agarose gel containing 1 mL 0.1% cresol purple (Titan Media) in clear plastic containers. A size #15K file (Dentsply) was placed at the WL in canal to prevent the agarose gel from getting into the canals. Hundred anterior teeth were randomly divided into six groups as follows:
Group I – NI (n = 20)
See AlsoEffect of the Use of Intranasal Spray of Essential Oils in Patients with Perennial Allergic Rhinitis: A Prospective StudyNasal Saline Irrigation in people with Common Cold: A Complete How-to Guide and Its Benefits - The Kingsley ClinicNasal Saline Irrigation in people with Rhinitis: A Complete How-to Guide and Its Benefits - The Kingsley ClinicDIY Health: Is Tap Water Okay for Neti Pots? Expert Insights Revealed - HomeFixMagicGroup II – PUI (n = 20)
Group III – PSI (n = 20)
Group IV – NP (n = 20)
Group V – positive control (n = 10)
Group VI – negative control (n = 10).
Chemomechanical preparation was done with the Crown-Down technique using rotary ProTaper (Dentsply Maillefer) system till F3. Apical patency was maintained by passing a #15 K file to the WL after each rotary instrument. In all groups, 12 ml of 3% NaOCl was delivered for 180 s [Figure 1].
Figure 1.
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Final irrigation
Group I – Needle irrigation
3% NaOCl was delivered using a 5-ml syringe with a 27 G needle (Dispovan, India) placed just short of WL.
Group II – Passive ultrasonic irrigation
Irrigant was delivered in the canal using a 5 ml syringe with a 27 G needle placed at coronal third. Then, U files (size #30) were inserted in the canal up to the WL and then activated at power setting 6 for 30 s.
Group III – Passive subsonic irrigation
Irrigant was delivered in the canal similar to the procedure used in Group II. Then, EndoActivator polymer tip #3 was inserted in canal up to WL and was set at 10,000 cycles/min and activated for 30 s.
Group IV – Negative pressure
Irrigant was delivered in the canal with a master delivery tip. Then, the activation was being done with macrocannula followed by microcannula inserted up to the WL for 30 s.
Positive control
Before irrigation system testing, each sample tooth was embedded in the pH-sensitive gel for a positive control assessment to verify the potential for apical extrusion. Using a 5-ml syringe with a 27 G needle positioned at WL, 3% NaOCl was extruded until apical gel color change was visualized. Gel color change was immediately visualized, which confirmed positive control for each sample tooth.
Negative control
Negative control teeth were treated as described for the positive controls except that they were irrigated with 0.5 mL saline (pH = 7.2–7.4) over 30 s at the WL.
Extrusion assessment
Dye diffusion was standardized by doing gel photography 25 min after the NaOCl final irrigation with a digital camera (Canon PowerShot Sx720 h 20.3 MP) at a fixed distance (30 cm). Adobe Photoshop 7.0 software was used to determine the area of color changes (in pixels) by selecting the stained portion and histogram pixel count was recorded. Cresol purple changes its color from yellow (pH = 7.4) to purple (pH = 9) in response to the change in pH. This indicated the extrusion of NaOCl (pH = 11.4) into the gel [Figure 2].
Figure 2.
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Statistical analysis of the assessment of four different root canal irrigation techniques was carried out. The software used in the analysis was SPSS software, version 17.0 (Statistical Package for the Social Sciences Inc, Chicago, IL, USA) and P < 0.05 is considered as the level of statistical significance. The number of teeth showing NaOCl extrusion was calculated using the Chi-square test. The Kruskal–Wallis ANOVA test was used to compare mean pixel among various irrigation
RESULTS
All positive controls showed NaOCl extrusion, whereas negative controls did not show any extrusion (as there was no color change in the gel). Table 1 lists the mean and standard deviations of pixels among various irrigation techniques. The comparison of mean pixels among various irrigation techniques showed the maximum value for NI (211094) and minimum value for NP (27231). NI had statistically significant apical extrusion compared to PUI (P = 0.001), PSI (P = 0.001), and NP (P = 0.001) groups. On the contrary, NP irrigation showed the least amount of apical extrusion compared to NI (P = 0.001), PUI (P = 0.012), and PSI (P = 0.043). Although PUI showed a higher amount of apical extrusion compared to SI, there was no statistically significant difference between both groups (P = 0.610).
Table 1.
Comparison of mean pixel among various irrigation techniques using the Kruskal–Wallis ANOVA test
| Group | n | Mean | SD | SE | P |
|---|---|---|---|---|---|
| I | 10 | 211094.0000 | 16887.00319 | 5340.13929 | 0.001* |
| II | 8 | 52357.2500 | 2701.06644 | 954.97120 | |
| III | 4 | 35458.0000 | 2275.97334 | 1137.98667 | |
| IV | 2 | 27231.0000 | 2872.26775 | 2031.00000 | |
| I | |||||
| II | 0.001* | ||||
| III | 0.001* | ||||
| IV | 0.001* | ||||
| II | |||||
| III | 0.610 | ||||
| IV | 0.012* | ||||
| III | |||||
| IV | 0.043* | ||||
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*P<0.05, significant. SD: Standard deviation, SE: Standard error
DISCUSSION
The irrigant is delivered with or without its activation in all the irrigation techniques. Activation of irrigants helps in the mechanical cleaning of the root canal system by active fluid movement dynamics.[18] However, it may lead to an “Endodontic Flare-up” characterized by the development of pain, swelling, or both and is of sufficient severity to require an unscheduled visit for emergency treatment.[19] Hence, it is important to follow the guidelines for that particular irrigation system. NI system recommends gentle delivery of irrigant with loosely fitting needle short of WL.[20] In this study, the needle was placed around 2 mm short of the WL. In contrast, the PSI, PUI, and NP were used at the WL as recommended by the manufacturer.
Here, teeth were embedded in a 0.2% agarose gel (pH = 7.3–7.4), creating a closed system that more closely resembled the in vivo environment. Cresol purple content of this gel changes color at a pH of 9.0 when mixed with a pH-sensitive dye. The teeth were instrumented and irrigated in a similar manner to that in the clinical setting by one operator to reduce variability. In the earlier studies, irrigant extrusion quantification was done in terms of volume, weight, or concentration.[16] On the contrary, the present study used linear measurements to visually evaluate the definite degree of extruded NaOCl. On the basis of similar apical extrusion studies that used a pH-sensitive gel, 3% NaOCl was selected to ensure adequate visualization of color change if extrusion occurred. Here, the number of pixels as well as teeth displaying the apical extrusion was evaluated. The evaluation of pixel number is more significant as it is directly linked to the quantity of extrusion and the larger the quantity of extrusion and the greater the injury to the periapical tissues.[21] Apical extrusion may occur in any irrigation procedure as shown in our results, but if the amount of extrusion is small, the periapical tissues would not be harmed, and the patients would show no clinical symptoms.[21]
As reported in the literature, the wide standard deviation seen in NI depicted its greatest potential for NaOCl accidents.[22] The results suggest that extrusion potential by PUI or PSI to a lesser extent could pose complications when compared with an NP system like the EndoVac as shown previously.[14,23] Because of the differences in the irrigation systems tested, it was not fully possible to standardize the volume and rate of irrigant expression, but it was possible to keep a standard time of 180 s between irrigation start and digital photo. It is not reasonable to compare delivery methods with activation methods in terms of extrusion unless the delivery before activation is also considered. NP and NI are irrigant delivery devices, whereas PSI and PUI are irrigant activation techniques that need other devices for the delivery of irrigant. Within these definitions, PSI produced less extrusion than fellow activation method PUI, but it was not statistically significant. In PUI, acoustic streaming creates a small, intense, and circular fluid movement (i.e., eddy flow) around the instruments. The eddying occurs closer to the tip than in the coronal end of the file, with an apically directed flow at the tip. This may be the possible explanation for the NaOCl extrusion in the PUI group. Regardless of activation or delivery, PSI/PUI (activation method) produced significantly more extrusion than NP (delivery method). NP system leads to the apical suction effect of the endodontic irrigants down and along the walls of the root canal creating a rapid turbulent cascade effect. This creates a steady flow of irrigation solution through the entire root canal, without extrusion.
The information gained from this study can be used as part of a decision-making process for final irrigation system selection to lessen the possibility of apical extrusion, and in cases, the apical control of irrigants is paramount such as teeth with resorption, perforation defects, or open apices.
CONCLUSIONS
Conventional 27-G NI has the greatest potential for NaOCl accidents compared to all other three methods. EndoVac produced less extrusion than EndoActivator and PUI. Activation methods (PSI and PUI) produced significantly more NaOCl accidents compared to delivery method (NP). Due consideration should be given to the potential for apical extrusion of the irrigant before the selection of an irrigation system. pH-sensitive gel model used in this study has satisfactory sensitivity to extricate even minor variances of NaOCl extrusion. Evaluation of the number of pixels is more significant than the calculation of the total number of teeth displaying the apical extrusion.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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