Comparison of efficacy of various root canal irrigation systems in removal of smear layer generated at apical third: An SEM study.

AIM: The aim of the study is to compare the efficacy of different irrigation systems comparing irrigation with syringe and needle (Dispo Van), Max-I-Probe needle (Dentsply Maillefer), EndoActivator (Dentsply Maillefer), and EndoVac (Sybron Endo) in removing the smear layer generated at apical third.
MATERIALS AND METHODS: Instrumentation was done in 40 extracted premolars using different irrigation regimes (Group 1, saline and syringe; Group 2, Max-I-Probe needles with NaOCl and ethylenediaminetetraacetic acid (EDTA); Group 3, irrigant activation with EndoActivator using needlesNaOCl and EDTA; and Group 4, irrigation with EndoVac using needles NaOCl and EDTA). STATISTICAL ANALYSIS USED: The percentage of debris was seen with scanning electron microscope (SEM) and evaluated using one-way analysis of variance (ANOVA), Kruskal-Wallis test, followed by Mann-Whitney test for significance.
RESULTS: The mean score ± standard deviation for the conventional group was 2.8 ± 0.42 with median value of 3.00 (2-3). The results for the Max-I-Probe needle group were 2.3 ± 0.48 with median value of 2.00 (2-3) The mean debris score for EndoActivator group were 0.8 ± 0.42 with median value of 1 (0-1). The mean debris score for EndoVac group were 0.4 ± 0.52 with median value of 1 (0-1).
CONCLUSION: EndoVac and EndoActivator performed much better than other available systems in removing the smear layer from apical third. So they should be incorporated as a regular part of the irrigation regime.

INTRODUCTION

Success of root canal treatment depends on good biomechanical preparation.[1] Despite all efforts, it is evident that bacteria can still survive in certain inaccessible areas.[2] Byström et al., established that mechanical instrumentation alone is inefficient and supporting actions of disinfectants such as NaOCl are still necessary. Chow showed that the efficacy of apical irrigation is directly related to the depth of insertion of the needle, which at times presents a challenge to the clinician.[3]

The aim of this in vitro study was to evaluate the efficacy of various irrigation systems in removing the smear layer generated at apical third.

MATERIALS AND METHODS

Freshly extracted, 40 single rooted teeth with one canal (mandibular premolars) confirmed with intra oral per apical (IOPA) in buccolingual and mesiodistal direction were taken. After cleaning the teeth of calculus and extraneous soft tissue, the teeth were stored in 10% buffered formalin solution. Access opening was done with the help of EndoAccess and Endo Z burs (Dentsply Maillefer). Biomechanical preparation was done in all specimens to size of F4 ProTaper rotary files (Dentsply Maillefer). Tenteeth were allocated to each group that confirmed the preparation size of F4 with apical gauging with hand file ISO size # 40.

Group 1: Conventional irrigation with needle and syringe using saline.

Group 2: Irrigation with Max-I-Probe needles using NaOCl and ethylenediaminetetraacetic acid (EDTA).

Group 3: Irrigant activation with EndoActivator using NaOCl and EDTA.

Group 4: Irrigation with EndoVac using NaOCl and EDTA.

Irrigation protocols

In all four groups, ProTaper sequence was used according to manufacturer's instructions

In Group 1, irrigation with normal saline using 24 gauge syringe and needle (DispoVan) followed by recapitulation and reirrigation was done after each instrumentation.

In Group 2, Max-I-Probe needles (Dentsply Maillefer) were used instead of normal syringe and needle. Irrigation with NaOCl and EDTA with intervening saline solution to flush out any remnants of previous irrigant was used; followed by recapitulation and reirrigation after each instrumentation. After completion of the biomechanical preparation, the canal was soaked with NaOCl for 1 min. It was then washed thoroughly with normal saline and dried with paper points followed by 1 min of soaking with EDTA. Another round of washing and soaking was done, and finally tooth was dried with paper points. All the files were coated with EDTA gel prior to insertion.

In Group 3, same procedure was followed as in Group 2. Since the preparation was done till F4, EndoActivator tip size 35/04 was chosen for irrigant activation. The tip was introduced till 2mm short of working length (WL) in an already flooded canal and irrigant was activated for a period of 30 s. Canal was then washed with saline solution and dried with paper points. Another round of activation was given. Soaking of the canals was done in a similar fashion as Group 2.

In Group 4 while instrumentation, macrocannula was utilized to remove coarse debris using apical negative pressure after instrumentation and was used along with master delivery tip. The macrocannula was taken to full WL and was moved 2mm with an “up and down” action every 6 s as the canals are flushed with NaOCl. The microcannula was used at the end with the combination of three rinses using NaOCl and EDTA and washing with saline, and drying with paper points after every irrigant used.

Preparation of the samples

The coronal portions of the teeth were sectioned with diamond disks. The teeth were thensplit along the groove with the help of mallet and chisel; apical third was marked on the teeth and were cut in horizontal direction with the diamond disks without perforating the canal. These specimens were stored in graded percentages of ethanol solution in 50, 70, and 90% and absolute alcohol; and then dipped in acetone solution for dehydrating and cleaning the specimens. These specimens were then mounted on the brass stubs for gold sputtering with 100Å of gold palladium and were viewed under scanning electron microscope (SEM).

Scoring criteria

Score 0: No smear layer, more than 80% of the dentinal tubules open and free of debris.

Score 1: Minor smear layer, more than 50% of the dentinal tubules open and free of debris.

Score 2: Heavy smear layer, more than 30% of the dentinal tubules open and free of debris.

Score 3: Maximum obliteration of dentinal tubules.

Statistical Methods

One-way analysis of variance (ANOVA) followed by intergroup comparison using Kruskal-Wallis test and Mann-Whitney test for significance was used to test differences between outcomes of different groups.

RESULTS

Mean values reported with ANOVA test between the groups were 13.36 and within groups was 0.214 [Table 1]. Intergroup comparison showed significant difference between Group 1 and 3, 1 and 4, 2 and 3, and 2 and 4 as significance value (P) was less than 0.05. The results were insignificant for Groups 1 and 2, and 3 and 4 [Table 2 and Figure 1]. Maximum efficacy was shown by Group 4 samples followed by Groups 3, 2, and 1 [Table 3 and Figure 2].

Table 1

ANOVA: Level of significance

Table 2

Significance (P) value for all the groups

Figure 1

1: P-value

Table 3

Frequency and percentage of debris score for each group

Figure 2

Score value

DISCUSSION

The goal of root canal instrumentation is to obtain a continuoustapering funnel, flowing with the shape of the original canal from the coronal access to the apex. Optimal canal sanitization is based on the combined use of mechanical instrumentation and two or several irrigating solutions, in a specific sequence, to predictably obtain the goals of biomechanical preparation. In a landmark article specifically devoted to root canal irrigation, Louis Grossman stated “mechanical instrumentation should be followed by irrigation of the canal in order to wash out fragments of pulp tissue and dentinal shavings”.[4]

Irrigants have traditionally been delivered into the rootcanal space using syringes and needles of different size and tip design. Research have shown that this classic approach typically results in ineffective irrigation, particularly in peripheral areas such as anastomoses between canals, fins, and the most apical part of the main root canal.[5] Material that remains untouched or compacted into the root canal anatomy consists of both organic and inorganic components. The results obtained in this study showed that conventional irrigation using saline with needles/syringes performed the least in removing debris and smear layer from the root canal [Figure 3a]. Since the studies have shown that saline is neither an organic tissue solvent nor does it have a smear layer removing efficacy, its use in clinical situations could be limited to only flushing out loose debris from the root canal system.

Figure 3

(a) SEM image Group 1. SEM = Scanning electron microscopy (b)SEM image Group 2

Manual dynamic irrigation is shown to be significantly more effective than an automated, dynamic irrigation system and static irrigation.[6] Max-I-Probe irrigation needle are designed to create a turbulence to dislodge and help flush the bacteria and other debris out of the canal. They help minimize the risk of accidental extrusion of the solution into the periapical tissue as compared to conventional needle.[7] When irrigation was done using Max-I-Probe needles with NaOCl and EDTA in the present study, the results revealed that although it performed better than irrigation with tip vented needles, it was not as effective in removing the smear layer as with the machine assisted irrigation methods. In the SEM pictures, only few dispersed open and clean dentinal tubules could be seen, but most of the area was covered with debris and smear layer; but revealed a comparatively cleaner surface as compared to conventional group[Figure 3b].

The EndoActivator system has been reported to provide deeper penetration of an irrigant to all areas of the endodontic space, and effectively clean debris from lateral canals, remove the smear layer and dislodge clumps of simulated biofilm (Caron 2007). A possible explanation for irrigant activation giving cleaner canals is that higher frequency results in higher flow velocity which helps in dislodging the debris more efficiently.[8] The results of the present study showed thatirrigation with EndoActivator showed more than 50% of the dentinal tubules open and patent [Figure 4a]. It removed smear layer better than last two groups; may be due to deeper penetration of an irrigant to all areas of the endodontic space and effectively clean debris from lateral canals, remove the smear layer, and dislodge clumps of simulated biofilm. Its ability to create sonic waves in irrigating solutions deposited inside of the root canal might aid in the killing of bacteria and debridement of necrotic tissue (SEM pictures). The results are in accordance with the study done by Mathew et al., to evaluate antimicrobial efficacy where EndoActivator showed better results (1.79 ± 0.21 × 106 CFU/ml) than conventional needle irrigation (2.45 ± 0.22 × 106 CFU/ml).[9] This was also confirmed in the study where significantly greater efficiency of the EndoActivator against intracanal Enterococcus faecalis biofilm compared to the NaOCl irrigation alone was found.[10] Similar bacterial load reduction was reported by Pasqualini et al., (2010). These results indicate that activation of the irrigant enhances the removal of dentin debris from the apical root canal.[8] Recently, Rodig et al., found that sonic and ultrasonic systems improved smear layer removal only in the straight coronal portion of curved root canals.

Figure 4

(a) SEM image Group 3 (b) SEM image Group 4

When compared with ultrasonics, multiple positive and negative nodes along the length of an activated ultrasonic instrument served to undesirably dampen the amplitude, especially when the instrument touched the lateral walls of a shaped canal. On the contrary, sonic and subsonic activation operates with one single positive and negative node, produced two alpha routinely, and the movement of the vibratory instrument was not influenced by lateral wall contact.[11] Whereas the insert in the ultrasound system is made of metal alloys, EndoActivator has polymer-based tips that do not damage the canal wall. Moreover, the high frequency generated by ultrasound can result in greater extrusion of debris.

On the other hand, some studies have demonstrated that sonic and ultrasonic instrumentation is not better than hand instrumentation in disinfecting or cleaningroot canals.[10]

When irrigation was done with EndoVac, the results ofSEM showed more than 80% of the dentinal tubules open and free of smear layer [Figure 4b]. This may be due to the negative pressure it creates in the canal, which takes the irrigant to the full WL. Since the irrigant comes in direct contact with the entire dentinal walls, the results are in support of the literature and research showing the maximum efficacy of EndoVac. The results of this present study are in accordance with the study done by Siu and Baumgartner(2010), which showed that EndoVac irrigation resulted in significantly less debris at 1 mm from WL compared with conventional needle irrigation, but there was no significant difference at the 3-mm level.[121314] Similar results between EndoVac and Max-I-Probe needles were seen in another study done by Saini et al., where EndoVac showed least percentage of debris at all levels.[15] Some studies have also quoted similar or even higher efficacy with EndoActivator than EndoVac. The explanation for such phenomenon can be given on the basis that during sonic activation, vigorous fluid agitation was observed in the pulp chamber. Vibrating the tip in combination with moving the tip up and down in short vertical strokes, synergistically produced a hydrodynamic phenomenon which could be the reason for efficient performance of the sonic protocol.[16]

CONCLUSION

In conclusion, machine-assisted irrigation devices and activation of irrigant resulted in better irrigation at the apical third level in both quantity and quality, thus being more efficient in removing the smear layer. Traditional needle irrigation alone showed less penetration of irrigant into the apical third and was limited to the level of penetration of the needle. Side-vented needles did not show much difference than their tip-vented counterparts.