Efficiency of Different Endodontic Irrigation and Activation Systems, Self-Adjusting File Instrumentation/Irrigation System, and XP-Endo Finisher in Removal of the Intracanal Smear Layer: An Ex vivo Scanning Electron Microscope Study.

AIM: This ex vivo study was designed to evaluate and compare different endodontic irrigation and activation systems, the self-adjusting file (SAF) instrumentation/irrigation system, and XP-endo finisher for removal of intracanal smear layer.
MATERIALS AND METHODS: Fifty recently extracted, noncarious human intact single-rooted premolars were selected and divided into five groups (n = 10) according to the root canal irrigation systems; syringe and needle irrigation, passive ultrasonic irrigation (PUI), EndoVac irrigation system, SAF system, and XP-endo finisher. All groups were prepared to apical size F4 file except for the SAF group which was prepared to apical size 20 K-file and then instrumented with the SAF file. Each sample was subjected to final irrigation using different irrigation/activation systems. After splitting the samples, one half of each root was selected for examination under scanning electron microscope. The irrigation systems were compared using the Fisher's exact test with significance set at P < 0.05.
RESULTS: In the coronal part, there was no difference among the groups. In the mid-root section, the results of the PUI, EndoVac, SAF, and XP-endo finisher groups tended to be better than syringe and needle irrigation, but the difference was not significant. The apical part of the canal, the SAF system, and XP-endo finisher group seemed to be cleaner than those of the EndoVac group, but this difference was not significant.
CONCLUSIONS: Within the limitations of the present study, SAF system and XP-endo finisher group cleaned the apical part of the canal more efficiently than EndoVac, PUI, and syringe and needle irrigation. Copyright:

INTRODUCTION

Cleaning and shaping of the root canal system is very important step in root canal treatment. It helps to remove bacteria, debris from root canal systems, and disinfecting the root canal system. Thorough cleaning of root canal system is main prerequisite of any effective irrigation system. Iirrigation system should deliver sufficient volume of irrigant all the way to working length, have adequate flow and to be effective in debriding the complete root canal system.[1]

Manual delivery and agitation techniques and machine-assisted agitation devices are two main divisions in root canal irrigation systems.[2] Manual irrigation includes positive pressure irrigation, commonly performed with a syringe and a side-vented needle. On the other hand, machine-assisted irrigation techniques include sonic and ultrasonic as well as newer systems such as apical negative pressure irrigation and the plastic rotary file.[34]

Cul-de-sac configuration present a special challenge in the apical third of root canal, and several studies have indicated that syringe and needle irrigation tends to leave this part of the canal covered with smear layer and debris.[5]

A newly developed self-adjusting file (SAF) (ReDent-Nova, Raannana, Israel) is operated with continuous.

Flow of irrigation through the hollow file; it also leaves the surface of the canal covered with smear layer. However, when operated with the continuous flow of irrigants, alternating between sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid (EDTA), this system resulted in root canal walls that were free of debris and almost completely free of the smear layer.[6] The SAF was developed to conquer the inherent problems of the rotary nickel–titanium (NiTi) instruments.[7] It includes cleaning and shaping, i.e., irrigation and instrumentation of root canal systems in the same device.[89]

Studies using micro-computed tomography (CT) technologies show that standard NiTi files manage to clean just 45%–55% of the canal walls, leaving debris and bacteria to accumulate in areas left untouched. However, the use of XP-endo finisher following a root canal preparation improves cleaning of the root canal while preserving dentin.

The objective of this ex vivo study was to evaluate and compare conventional syringe and needle irrigation, passive ultrasonic irrigation (PUI), EndoVac irrigation, SAF system, and XP-endo finisher with conventional syringe and needle irrigation for the removal of intracanal smear layer.

MATERIALS AND METHODS

A total of fifty recently extracted, noncarious human intact premolars were selected. Endodontic access was obtained with round diamond bur and #15 K-file was introduced into the root canal until the tip was just visible at the apical foramen. Working lengths were set by deducting 1 mm from lengths of the files when they extruded just beyond the apical foramina. Crowns were sectioned using diamond disc to obtain a standard working length of 16 mm for all samples. To simulate clinical conditions, apices were sealed with hot glue.

Forty teeth were instrumented with a rotary NiTi files using crown down technique till F4. These roots were randomly divided into four groups of ten roots each. The ten teeth in the SAF group was first instrumented manually up to #20 K-file, according to manufacturer instructions, followed by instrumentation with the SAF which was operated in the canal for 4 min and with continuous irrigation with 5.25% NaOCl at 5 Ml/min.

Then, each sample was subjected to final irrigation using different irrigation systems with 5 mL 5.25% NaOCl, followed by 5 mL of 17% EDTA, followed by 5 mL 5.25% NaOCl and 0.9% normal saline.[5]

Grouping

After the completion of preparation, a total of fifty samples were distributed into five groups of ten teeth each.

Final syringe and needle irrigation

Final irrigation was done with 5 mL 5.25% NaOCl, followed by 5 mL of 17% EDTA, followed by 5 mL 5.25% NaOCl. Irrigation was done using syringe (Unolock, Hindustan syringes, Faridabad, India) adapted with 26G monojet endodontic irrigation needle (Tyco Healthcare, Gosport, UK); no activation was applied in this group, which served as control.[10]

Final irrigation with ultrasonic activation

Final irrigation was conducted with passive ultrasonic activation of the irrigants, using Minipiezon ultrasonic irrigation system (EMS, Nyon, Switzerland), adapted with a #20 Irrisafe ultrasonic files (Satelec, Acteon, Merignac, France). The ultrasonic file was placed into the canal 1 mm short of working length without touching the walls and was activated at power setting of 4.

The final irrigation consisted of 5 mL of 5.25% NaOCl with 1 min of activation. This was followed by 5 mL 17% EDTA, with 1 min activation and then by 5 mL of 5.25% NaOCl which was also activated for 1 min.[11]

Final irrigation with the EndoVac system

Final irrigation was conducted with the EndoVac (Discuss dental, Culver City, CA) which was used according to manufacturer's instructions. The procedure consisted of four cycles of irrigation, each beginning with 30 s of vacuum-assisted irrigation followed by 30 s of “soaking” (leaving the solution in the canal with no action). The first cycle was done using the macrocannula which was inserted to 1 mm from working length, while the three following cycles were performed with the microcannula which was inserted to 9 mm from working length. In the first and second cycles, 5.25% NaOCl was used. In the third cycle, 17% EDTA was used which was followed by the forth cycle, in which 5.25% NaOCl was used again.[12]

Final irrigation with self-adjusting file system

The final irrigation was conducted within the SAF instrumentation/irrigation protocol. A Kavo Gentle power low-speed handpiece (Kaltenbach and Voigt, Biberach, Germany) was connected to the RDT3 head (ReDent-Nova). Continuous irrigation with 5.25% NaOCl was performed for 4 min, at a flow rate of 5 mL per min, followed by 30 s of 17% EDTA and then 30 s of 5.25% NaOCl using an irrigation pump (VATEA; ReDent-Nova). Throughout the procedure, the SAF was vibrating at 5000 vibrations per min and used with pecking motion to working length.[13]

Final irrigation with XP-endo finisher and syringe and needle irrigation

For final irrigation with XP-endo finisher and syringe and needle irrigation, the access cavity was filled with irrigant only after the XP-endo finisher is in the canal. XP-endo Finisher (FKG Dentaire SA) was used for approximately 1 min, using slow and gentle 7–8 mm lengthwise movements to contact the full length of the canal. Final irrigation was done with 5 mL 5.25% NaOCl, followed by 5 mL of 17% EDTA, followed by 5 mL 5.25% NaOCl. Irrigation was done using syringe (Unolock, Hindustan syringes, Faridabad, India) adapted with 26G monojet endodontic irrigation needle (Tyco Healthcare, Gosport, UK).

At the end, all groups were irrigated with 5 mL 0.9% normal saline and dried with absorbent paper points.

Splitting the samples

Deep grooves were made on the buccal and palatal surfaces of the roots, using diamond discs, without perforating into the canal. The roots were then split longitudinally using a chisel. One half of each root was selected for examination under scanning electron microscope (SEM).[11]

Scanning electron microscope evaluation

After assembly on coded stubs, the specimens were platinum sputtered (JEOL, JFC-1600 Auto Fine Coater, Tokyo, Japan) and examined under a SEM at ×1000 magnification (JEOL, JSM-7600F, Tokyo, Japan). The dentinal wall of the coronal, middle, and apical thirds was observed for the presence/absence of smear layer and visualization of the entrance to the dentinal tubules and representing photomicrographs were taken.

The images were examined and scored according to the criteria given by Hulsmann et al.[14]

Score 1: Dentinal tubules completely open

Score 2: More than 50% of dentinal tubules open

Score 3: Less than 50% of dentinal tubules open

Score 4: Almost all dentinal tubules covered with smear layer.

Scoring was done by three independent examiners who were blinded as to the group to which each specimen belonged. Interexaminer agreement was 95% for the smear layer removal (Kappa test). When disagreement occurred as to the score of a given specimen (rarely), the issue was discussed and agreement reached.

RESULTS

The five groups were compared to each other at the coronal, mid-root, and apical part of the canal. Fisher's exact test for nonparametric values was used for this comparison with significance set at 0.05. For purpose of this analysis, the scores were grouped into two groups [Table 1]: “clean or almost clean” which included scores “1” and “2” and “covered with smear layer” which included scores “3” and “4.”

Table 1

Comparison of Percentage of smear layer removal among the test irrigation systems at coronal, middle and apical third of the root canal system

Score	Grouped	Syringe & Needle		PUI		EndoVac		SAF System		Xp endoSystem
Coronal
1	Clean&Almost Clean	0*	**90%	0	90%	1	100%	3	100%	2	100%
2		9		9		9		7		8
3	Covered with Smear Layer	1	10%	1	10%	0	0	0	0	0	0
4		0		0		0		0		0
Midroot
1	Clean&Almost Clean	0	70%	0	80%	1	90%	2	100%	1	90%
2		7		8		8		8		8
3	Covered with Smear Layer	3	30%	2	20%	1	10%	0	0	1	0
4		0		0		0		0		0
Apical
1	Clean&Almost Clean	0	0	0	0	0	60%	0	80%	0	70%
2		0		0		6		8		7
3	Covered with Smear Layer	0	100%	7	100%	4	40%	2	20%	3	30%
4		10		3		0		0		0

1 to 4 - scores according by Hulsmann et al.[14] *Number of samples showing with a given score, **Percent samples showing with a given grouped score. PUI: Passive ultrasonic irrigation, SAF: Self-adjusting file

The results of the SEM evaluation are presented in Table 1. In the coronal part, there was no difference among the groups [Figure 1]. In the mid-root section, the results of the PUI, EndoVac, SAF, and XP-endo finisher groups tended to be better than syringe and needle irrigation, but the difference was not significant. At apical third region, none of the groups presented with dentin surface totally devoid of smear layer [Score “1,” Table 1], but in the EndoVac, SAF, and XP-endo finisher groups, the dentin surface at the apical part of the canal was cleaner and presented with “clean and almost clean” score in 60%, 80%, and 70% of the cases, respectively, which differed significantly from the other groups (P = 0.011 and P = 0.001, respectively). The walls of the apical part of the canal in the SAF system and XP-endo finisher group seemed to be cleaner than those of the EndoVac group [Table 1], but this difference was not significant.

Figure 1

(a) Syringe and needle irrigation at coronal third level, (b) Syringe and needle irrigation at mid-root level, (c) Syringe and needle irrigation at apical third level, (d) passive ultrasonic irrigation at coronal third level, (e) passive ultrasonic irrigation at mid-root level, (f) passive ultrasonic irrigation at apical third level, (g) EndoVac at coronal third level, (h) EndoVac at mid-root level, (i) EndoVac at apical third level, (j) self-adjusting file at coronal third level, (k) self-adjusting file at mid-root level, (l) self-adjusting file at apical third level. (m) XP endo at coronal third level, (n) XP endo at mid-root level, (o) XP endo at apical third level

DISCUSSION

The protocols suggested for the studied irrigation/activation systems differ substantially from each other, so when designing this study, exact similarity between the groups was not possible. The protocol for each group was made as similar as possible to the other groups and as similar as possible to the way each irrigation system is applied clinically.

The results of this study revealed no significant difference in the SAF group and XP-endo finisher for the removal of intracanal smear layer at the apical third region. Better results were seen in the SAF system, most likely because the hollow file allowed for the continuous irrigation of the root canal throughout the procedure, with additional activation of the irrigant by its vibrating motion that creates turbulence in the root canal.[13] The chosen irrigation fluid enters the file through a free-rotating hub and is continuously replaced throughout the procedure, thus providing a fully active, fresh supply of NaOCl, and chelator solution to the apical third part of the canal. SAF file induces a scrubbing motion on the canal walls that must have obviously contributed to the exceptionally clean surface that resulted even in the cul de sac portion of the canal.[13] Metzger et al.[13] also showed that the SAF system with continuous irrigation coupled with alternating NaOCl and EDTA treatment resulted in a clean and mostly smear layer-free dentinal surface in all parts of the root canal. Iriboz et al.[15] reported using the SAF instrument; flat-oval canals were prepared homogenously and circumferentially.

The results of the XP-endo Finisher is because of it is flexibility, it can expand its reach 6 mm in diameter or 100-fold of an equivalent sized file. This is why XP-endo finisher allows mechanical cleaning of the canal in areas previously impossible to reach. Because of its small core size – ISO 25 in diameter – and its zero taper, the file benefits from incredible flexibility and shows unparalleled resistance to cyclic fatigue. In addition, the file will contact and clean the dentin but not change the original shape of the canal. Unprecedented resistance to instrument fatigue occours because of its zero taper and the ability of the file to work in mixed M and A phases (exclusive FKG MaxWire alloy).

Activation of the irrigant in the EndoVac group has been shown to be more effective than PUI and syringe and needle irrigation system. For EndoVac group, the apical negative pressure pulls the irrigant down the canal walls toward the apex, creating a rapid turbulent current force toward the terminus of the microcannula. The orifices of the microcannula evacuate debris from the closed end of the canal systems. This mechanism helps to overcome the vapor lock, thus enabling effective irrigation.[16]

”EndoVac was significantly better in removing debris than Navi Tip in the apical third of the root canal. EndoVac system cleaned the apical part of the canal more efficiently than sonic, ultrasonic, and syringe and needle irrigation”.[17]

The results of this study have several clinical implications. Most importantly, conventional syringe and needle irrigation system does not provide adequate cleaning of the canal system, especially in the apical third region. This is concerning because only 45% of endodontists utilize adjunctive ultrasonic or sonic activation, with 55% using only conventional syringe and needle irrigation system. The study's results also suggest that the use of ultrasonic irrigant activation removes more smear layer than conventional syringe and needle irrigation system.[18]

In the present study, the conventional syringe and needle irrigation system showed a larger amount of debris and smear layer at apical, middle, and coronal level than any other system because flushing action of syringe irrigation is relatively weak and dependent not only on the anatomy of the root canal but also on the depth of placement and the diameter of the needle. It has been shown that irrigants can only progress 1 mm beyond the tip of the needle.[19]

CONCLUSIONS

Within the constraints of the present study, it can be concluded that none of the techniques completely removed all the smear layer from root canal walls at the apical part of the canal. The SAF system and XP-endo finisher group showed significantly better cleaning than EndoVac, ultrasonic, and syringe and needle irrigation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.