Comparative Evaluation of the Efficacy of Novel Root Canal Irrigation Techniques on Reduction of Enterococcus faecalis Count: An In Vitro Study

INTRODUCTION

The primary objective of nonsurgical endodontic treatment relies in eradication of microbial infection and preservation of vitality of pulp tissue. Endodontic success relies on the implementation of “endodontic triad,” which includes effective instrumentation, disinfection, and obturation.¹

The complexity of the canal anatomy with fins, lateral canals, and apical deltas makes it inaccessible for instrumentation. Disinfection protocols comprise of removal of residual tissue, microbes, and debris to reduce the bacterial load.²

The root canal flora is dominated by obligate anaerobic bacteria with mixed population. Enterococcus faecalis has been associated with secondary infections of the failed endodontic treatment.³ The unique feature of the bacteria depends on the distance traveled from the surface to the internal aspects of the radicular dentin.⁴

The study has been designed to review the efficacy of conventional irrigation system on reduction of bacterial load with a novel irrigation system.⁵ Measures to improve the replenishment and exchange of irrigant that arises due to vapor lock effect in the apical third of the root canal system has been initiated.⁶

Dynamic irrigant activation system comprises of manual and machine-assisted activation devices. Manual irrigation techniques tested in our study includes Max I probe and Navitip FX, which works on the principle of delivering the irrigant with positive pressure in the apical third of the root canal system.⁷

The main advantage of Maxi I probe is that it has side vented needle delivering the irrigant, laterally aiding in penetration into the canal aberrations. The main disadvantage of NaviTipFX is that it delivers the irrigant short of apex.

Machine-assisted agitation devices such as Endoactivator System (EA) uses sonic energy for activation of irrigant and has been found to have canal free from debris. The compact design enhances the effective delivery of irrigant into the canal complexities without causing any alterations to the dentin substrate.

The Endovac system works on the negative pressure principle to suck out debris and aids in cleaning the prepared canal with less potential of irrigant leakage. The major disadvantages of Endovac system is related to technique sensitivity, difficulty in sterilization of device, and cost.

The study was designed in such a way to compare the different concepts, such as positive pressure vs negative pressure and irrigant activation concepts and its ability to assess the efficacy in reduction of E. faecalis count.

The aim of this in vitro study was to compare the effectiveness of three irrigation systems, namely, Endovac system, Max I probe, and Navitip FX in reduction of E. faecalis population.

MATERIALS AND METHODS

Sixty permanent maxillary incisors extracted for prosthodontic purposes were selected for this study. Teeth were debrided with ultrasonic scaler tips. Access cavity preparation was done with no. 2 round burs.

Root canal procedures were done in department of conservative dentistry and endodontics by the primary investigator, and colony-forming units counts were done in the microbiological laboratory by the microbiologist after blinding the materials used for the study.

Patency was established with 10 size K-file. Working length was standardized to 20 mm. The apical enlargement was done till 25 size, and the apical foramen was sealed with Type II GIC. The teeth were mounted in blocks made of self-cure resin. The samples were sterilized in autoclave for 20 minutes at 121°C.

RESULTS

The data were subjected to various statistical significance to interpret the significant differences among various irrigation systems.

One-way analysis of variance (ANOVA) was used to interpret the overall variance among the groups. It was not possible to identify the difference between the various groups with the help of the p values obtained from ANOVA.

To make a comparison of variance within the group, post hoc Tukey was employed. In our study, one-way ANOVA followed by Tukey HSD test showed statistically significant difference among experimental groups related to E. faecalis reduction in each group.

Mean E. faecalis count was highest with mean of 425 × 106 colony-forming units (CFUs)/mL] in NaviTipFX group.

Mean rank score for E. faecalis count was 210 × 106 colony-forming units (CFUs)/mL in Max-I-Probe group.

Mean rank score for E. faecalis counts was 156 × 106 colony-forming units (CFUs)/mL in Endoactivator group.

Mean rank score for E. faecalis reduction was lowest with mean 12 × 106 colony-forming units (CFUs)/mL] in Endovac group.

Among the experimental groups, group IV showed statistically significant difference in reduction of E. faecalis.

There were no statistical differences between them in reduction of E. faecalis in group I and group II compared, and the values are represented in Table 2.

DISCUSSION

The primary etiology of apical periodontitis arises due to localization of microbial agent in the apical portion of the root canal system. The management of irreversible pulpits aims to prevent the progression of infection into periapical region.⁷

Secondary apical periodontitis arises due to the exacerbating of residual bacterial load. The predominant bacteria from the secondary infection include Lactobacilli, Staphylococci, Enterococcus faecalis, and Propionibacterium.⁸

Enterococcus faecalis is a facultative gram-positive anaerobe with a prevalence of 22–77%. It has a potential to modulate the internal pH by an efficient proton pump. It has the capacity to travel deep in to the dentinal tubules and get lodged into the canal irregularities. The organism exhibits resistance pH variations and can last in the challenging and tough enivionment.⁹

The anatomical complexity necessitates employment of special mechanical aids to ensure thorough debridement. The mechanical instrumentation removes the necrotic and vital organic tissue and ensures the fulfillment of mechanical objectives.¹⁰ In this present study, the apical size was prepared with #40 ProTaper which has taper of 0.09, and this enlargement helps in placement of microcannula at the working length.

Byström et al. showed that apical enlargement size was directly proportional to volume of irrigant delivered. The majority of infection control mechanism depends on the irrigation techniques and devices to contribute to the reduction in microbial agents.¹¹

The irrigants used for removal of these materials must address both these organic and inorganic components, and the presence of biofilms in the uninstrumented canal can cause treatment failure.¹²

The removal of the inorganic component in the root canal is of primary importance because it allows penetration of the antimicrobial irrigants to areas of the dentin that may harbor bacteria.¹³

Sodium hypochlorite when used alone as an endodontic irrigant lacks action on the inorganic component and the dentinal debris which is formed during instrumentation.¹⁴

Ethylenediamine tetra-acetic acid (17% EDTA) acts predominantly on the inorganic portion of the root canal system. It also reduces the hydrophobicity and surface free energy of root dentin thereby reducing the adherence of E. faecalis to dentin.¹⁵

In the present study, regime of 3% sodium hypochlorite and 17% EDTA was used as final irrigation. In positive pressure technique, irrigant is expelled with pressure from the irrigation system.

Conventional syringe irrigation involves above principle to dispense the irrigant through needle of various sizes passively or with agitation. Mechanical flushing action is relatively weak to displace the debris and bacteria from the inaccessible areas and irregularities, thereby making thorough canal debridement difficult.¹⁶

The replenishment and exchange of irrigant in the apical third and the effectiveness of chemical debridement are dependent on the depth of penetration.¹⁷

They are less effective in cleaning the apical areas compared to the coronal areas of root canal systems. The close proximity of the needle tip to the apical tissue has a greater chance of apical extrusion of the irrigant.¹⁸

It is essential to develop delivery systems that improve the irrigant penetration to the inaccessible areas to ensure complete disinfection of the canal system with minimal in periapical tissues.¹⁹

Recently, NaviTip FX irrigation system has been into the market. The special design feature with brush helps to reach up to the apex and scrub the canal wall while concomitantly delivering the irrigant effectively to apex.²⁰

Max-I-Probe is an irrigation system with side vented and close-ended needle that delivers the irrigant laterally. The above design improves the availability of irrigant and reduces the apical leakage of the irrigant. Usman et al. showed that Max-I-probe was effective in displacing the bacteria from the root canal.²¹

Boutsioukis et al. had a valuable observation and concluded that the exchange of irrigant happens only 1 to 1.5 mm past a side-vented needle, and the irrigant beyond that point remains stagnant in his computational fluid dynamic model.²²

The Endoactivator system aids in penetration of an irrigant to inaccessible areas of the root canal system and helps in dislodgement of bacteria. The high-frequency sonic energy causes activation of irrigant and aids in dislodgment of microbes in an efficient manner. Previous studies have shown that more than 50% of the dentinal tubules remain open and patent. Its ability to create sonic waves in the root canal aids in the removal and reduction of bacteria along with the necrotic tissue debris.

Endovac is an irrigation system that works on the negative-pressure principle and has (1) Macrocannula of 0.55 mm in diameter/0.02 taper (2) Microcannula with diameter of 0.32 mm. Desai et al. compared the safety of different irrigation systems and concluded that Endovac is safe to work at working length.²³

Haapasalo et al. observed that volume requirements are unique to the delivery system.²⁴ In the present study, the Endovac [group IV] showed few numbers of bacterial colonies [with a mean of 12 × 10⁶ CFUs)/mL] and resulted in significant reduction of bacterial load than the other irrigation system.

Group I (Navitip FX) showed comparable reduction in the bacterial load [with a mean of 425 × 10⁶ CFUs/mL] which might be attributed to the scrubbing action of irrigation system. Similar results was reported by Al-Hadlaq et a1. and Zemner et al. who proved that brush-covered irrigation needle was more effective in achieving cleaner canals.

In Group II (Max-i-probe), there was significant reduction in bacteria load with a mean of 210 × 10⁶ CFUs)/mL. The probable reason may be attributed to its design, closed-ended, side-vented channel, which tends to deliver the irrigant laterally.

This unique design creates a turbulence that removed considerable number of bacteria on comparison with the needle irrigation.²⁵ Similar results were reported by Vinothkumar et al. who concluded that side vented was clinically effective than other irrigation devices.²⁶

Group III Endoactivator group showed with a mean of 156 × 106 colony-forming units (CFUs)/mL that when compared to other experimental group, it was effective in reduction of bacteria from the root canal.

Endovac irrigation system had maximum bacterial reduction, while the Endoactivator system showed comparable result that might be attributed due the differences in principle of irrigation technique along with position of irrigation device which was at the apex for the Endovac system.

LIMITATIONS OF THE STUDY

Usage of Endovac system in thin and curved roots in vivo needs to be warranted. Clinical trials investigating the effects in mixed bacterial community are required to determine the efficacy of disinfection protocols of teeth with apical periodontitis. Additionally, further investigations are also necessary test in vivo situation involving more number of clinical parameters.

CONCLUSION

It was found that all four irrigation delivery systems have been found to be effective in the reduction of E. faecalis. Endovac showed comparable efficacy in reduction of colony-forming units to that of other delivery systems used in the study. The results have to be validated with in vivo studies and clinical trials of larger sample size.

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