Comparison of the incidence of postoperative pain after using a continuous rotary system, a reciprocating system, and a Self-Adjusting File system in single-visit endodontics: A prospective randomized clinical trial.

AIM: The aim of this study is to compare the incidence of postoperative pain using the ProTaper Next (PTN), WaveOne Gold (WOG), and Self-Adjusting File (SAF) systems.
MATERIALS AND METHODS: Two hundred and fourteen patients with irreversible pulpitis were selected for single-visit endodontics. The teeth were blindly assigned to three groups based on the instrumentation system used: Group A (PTN), Group B (WOG), and Group C (SAF). Participants were asked to note the incidence of the pre- and postoperative pain on a visual analog scale at different time intervals. Paired t-test and one-way ANOVA were used along with post hoc Tukey's test.
RESULTS: The greatest mean pain in Group A (PTN) and Group B (WOG) was found to be maximum in the first 24 h with a significant reduction in pain at the subsequent observation time points of 48 h, 72 h, and 7 days. Group C (SAF) showed minimum pain followed by Group B followed by Group A which showed comparatively higher pain scores even at the end of 7 days.
CONCLUSIONS: In single-visit endodontics, SAF system may prove to be a better system compared with PTN and WOG as it produces minimal postoperative pain, thus improving the overall acceptance of endodontic treatment.

INTRODUCTION

The incidence of pain in the root canal treatment has been a matter of concern even with the inception of advanced endodontic instruments. Periradicular inflammation associated with apical extrusion of debris is one of the leading causes of postoperative pain.[1]

On literature search, there is a lack of clinical evidence comparing the postoperative pain after using different nickel–titanium systems such as ProTaper Next (PTN), WaveOne Gold (WOG), and Self-Adjusting File (SAF) which employ varied file design and motion kinematics. The null hypothesis tested was that there is no difference in the postoperative pain following the use of PTN, WOG, and SAF instrumentation systems. The aim of the study was, therefore, to compare the postinstrumentation pain following the use of PTN, WOG, and SAF.

MATERIALS AND METHODS

This in vivo study was conducted in the department of conservative dentistry and endodontics between February 2016 to September 2017 and approval was taken from the institutional ethical committee (55/2016).

Patients (aged between 18 and 55 years) reporting to the department were screened and selected based on the presence of symptomatic irreversible pulpitis with/without apical periodontitis, with no periapical lesion and fully matured roots in permanent posterior teeth (premolars and molars of both maxillary and mandibular arches). The diagnosis was confirmed using pulp vitality tests and radiographs.

Curved root canals of more than 25°, complex root canal morphology, teeth requiring retreatment, teeth with gross decay, mobility, uncooperative or medically compromised patients, and those under premedication with nonsteroidal anti-inflammatory drugs/opioid analgesics were excluded from the study.

The sample size calculation, based on an error of alpha = 0.05 and a power of 0.8, indicated that a sample size of 43 in each group would be required to detect a difference in the mean pain score of the three groups. To ensure a safe representative sample, 253 teeth, that is, 84 cases per file system were selected. However, 39 cases did not fulfill the established criteria, and hence, 214 cases were selected [Figure 1].

Figure 1

Consolidated Standards of Reporting Trials flow diagram for randomized clinical trials

After obtaining informed consent, the patients were randomly stratified using a computer-generated simple randomization procedure (www.random.org) into two groups of 71 each and one group of 72, which were further equally assigned to six postgraduate students, who were calibrated and trained to use different instrument systems. The randomized order of instrument interventions and standard operating protocol were concealed in opaque discrete envelopes by the staff nurse, which were later opened by the operators. Baseline parameters such as age, gender, and preinstrumentation pain scores using visual analog scale (VAS) (0–100 mm)[2] [Table 1], as suggested by previous articles,[234] were recorded by the operators in the case history sheets.

Table 1

Categorization of pain in accordance with visual analog scale

Before initiating the treatment, the treatment plan was explained, and all participants received a questionnaire (including VAS sheet) to record their assessment of pain 24, 48, 72 h, and 7 days after the treatment. The occurrence of pain was categorized as described by the patient conferring to the four levels (on the VAS) as shown in Table 1.

Treatment protocol

After administering local anesthesia (2% lidocaine 1:80,000 epinephrine), occlusal reduction (1 mm) was done. Following rubber dam application, an ideal access opening and glide path establishment were done. The working length was determined using an apex locator (Root ZX II) and confirmed radiographically.

Cleaning and shaping of root canals was done using PTN (DENTSPLY Tulsa Dental Specialties, Tulsa, USA) and SAF (ReDent Nova, Ra'anana, Israel) were driven by an endomotor X-SMART™ (Dentsply Maillefer, Ballaigues, Switzerland) (using RDT3 handpiece for SAF), whereas WOG (DENTSPLY Tulsa Dental Specialties, Tulsa, USA) instruments were used in reciprocating mode with endomotor X-SMART® Plus (Dentsply Maillefer, Ballaigues, Switzerland). Torque limits and rotation speed were set individually as per the manufacturer's instructions. Based on the initial apical binding file, the master apical file tip size for both PTN and WOG was standardized at #25 for narrow canals and #35–#40 for wide canals. For SAF, 1.5 mm was used for narrow and curved canals and 2 mm was used for large canals.

Intermittent irrigation with 10 ml of 5.25% NaOCl per canal was done using a 30G side-vented needle at 1 mm short of working length followed by the use of normal saline and 17% aqueous EDTA, which was activated using an EndoActivator (Dentsply Tulsa Dental Specialties, Tulsa, USA) for 1 min to remove the smear layer. A final flush with 5.25% NaOCl; followed by 0.9% saline solution was performed. Canals were dried with paper points, master cone radiographs were taken, and root canals were obturated using gutta-percha and resin sealer (AH-plus, Dentsply Maillefer, Ballaigues, Switzerland) following lateral compaction method. Postendodontic composite resin restoration was done after acceptable level of obturation was achieved as assessed radiographically.

No medication other than ibuprofen (400 mg), 6 hourly in the event of pain, was prescribed. Patients were contacted telephonically by the principal operator after 24, 48, and 72 h, and assessed clinically after 7 days. Status of postoperative pain was recorded, as described by the patient, according to the preestablished pain categories using VAS at each time points.

Statistical analysis

Interexaminer and intraexaminer reliability assessments were done and kappa values obtained were 0.78 and 0.82, respectively. Paired t-test was applied for comparison of mean VAS scores from preoperative to different time intervals for each group of file systems. Comparison of mean parametric values was done using one-way ANOVA for intergroup comparison along with post hoc Tukey's test. P < 0.05 was considered statistically significant in the present study.

RESULTS

The postinstrumentation pain values were lower than preinstrumentation values and the difference was statistically significant (P < 0.05). The highest mean postoperative pain scores were observed 24-h posttreatment in all the instrumentation groups with a significant decline thereafter [Figure 2 and Table 2].

Figure 2

Comparison of mean VAS Scores among PTN, WOG & SAF systems at different time intervals (Data can be obtained from Table 2)

Table 2

Mean visual analog scale scores of Group A, Group B, and Group C obtained at different time intervals

To obtain intergroup comparison, the results were subjected to post hoc Tukey's test in which Group C (SAF) showed a significantly lower mean VAS score when compared with Group A (PTN) (at all postoperative time points) and Group B (WOG) (at 48 h and 72 h only) (P < 0.05). The mean VAS scores were not significantly different between Group B and Group C at 24 h and 7 days. When comparing Group A and Group B, there was a significant reduction in the mean VAS score only after 7 days.

None of the 210 participants reported severe pain or flare-up during the period of the study [Figure 1].

DISCUSSION

The success of endodontic therapy is defined not only by the efficacy of cleaning, shaping, and obturation but also by the degree of postoperative discomfort. One of the major shortfalls confronted while evaluating postoperative pain is the subjective nature of this evaluation and the inherent difficulty in measuring pain.[5] Therefore, a comprehensive questionnaire was designed which could be fully understood by patients and should lend themselves to straightforward interpretation.[5]

The instrument systems used in this study were based on a close match in terms of tip size of the instruments to maintain standardization and to rule out the effect of varying tip diameters on postoperative pain.[678]

Single-visit endodontic treatment was chosen to maintain a simple uniform treatment protocol and to rule out the potential influence of intracanal medication.

Understanding that irrigation technique plays a crucial role in the treatment outcome, 30G close-ended, side-vented needles were employed in this study with PTN and WOG file systems to prevent periapical extrusion of debris, while SAF system used its inbuilt continuous irrigation.

Cold lateral compaction obturation technique was used as it is documented that this technique resulted in minimum postoperative pain in comparison with the thermal obturation techniques.[9] Pain perception is purely subjective depending on patient's threshold and variable experience modulated by multiple physical and psychological factors. In the current study, a VAS was selected due to its ease of use, validity, and reliability in measuring pain.[10]

Statistical analysis of the baseline parameters showed no significant difference among the groups [Figure 2 and Table 2], thus confirming equal and homogeneous distribution of the samples.

A significant reduction in postinstrumentation pain when compared to preoperative pain was observed at all the time intervals, namely, 24 h, 48 h, 72 h, and 7 days. The greatest mean pain in all the three study groups occurred in the first 24 h, with a significant reduction in pain ratings at the subsequent observation time points of 48 h, 72 h, and 7 days in accordance with a systematic review conducted by Pak and White.[11]

Postoperative pain associated with irreversible pulpitis is commonly associated with preparation procedures, arising from an immune response to the irrigant, microorganisms present in extruded debris, overinstrumentation, or foreign body reactions to filling materials.[678]

Previous studies demonstrated that all canal preparation techniques are associated with wide-ranging variability in debris extrusion depending on the mechanical systems used.[12131415] This could be attributed to differences in the cross-section, cutting-edge design, taper, tip type, configuration, concept of use, flexibility, alloy type, number of files used, kinematics, or cutting efficacy.[16] The alterations in these properties may be the determinants responsible for higher pain scores of Group A and Group B when compared to Group C.

The pain associated with periradicular inflammation due to extrusion of debris may also be attributed to substance P and calcitonin gene-related peptide which activates G protein-coupled receptors on nociceptors, leading to the sensitization or activation of neurons,[17] and these neuropeptides can cause peripheral sensitization characterized as hyperalgesia, allodynia, and spontaneous pain.[18] Furthermore, central sensitization is initiated by a barrage in C-fiber inputs with sufficient intensity and duration.

In the present study, superior results were observed with SAF system which may be attributed to the following:

The hollow file is operated with continuous irrigation provided by a special device (VATEA). The irrigant enters the file through a free-rotating hub and is continuously replaced, thus providing a fresh, fully active, supply of NaOCl and EDTA

There is no positive pressure as the solution easily escapes through openings in the lattice of the file

The fluid in the apical part of the root canal is continuously replaced by the file due to the vibrating motion of the file's delicate mesh within the fluid

This device activates the irrigant throughout the process

The potential piston effect of the file in the apical part of the canal is negligible when it is priorly prepared up to #20 K file, as 38% of the cross-section of the canal is free for backflow.[19]

Comparable results were observed with WOG on the 7th day in relation to SAF which may be attributed to its modification in the metallurgy, reciprocating action, minimum instrumentation, flexibility, and parallelogram-shaped cross-section (which reduces the dentin engagement maintaining one-point and two-point contacts).[20]

Acceptable results were also observed with PTN which may be attributed to its rectangular cross-section, offset design, and M-wire technology.[21]

In the present study, it was noted that comparatively higher VAS scores were observed with PTN at the end of 24 h, 48 h, and 72 h showing relatively higher scores even at the end of 7 days when compared to the other two file systems.

PTN has rectangular cross-section together with a decreasing taper at the coronal section has higher screw-in force and flexural rigidity. This may result in apical transportation in straight section in severely curved canals.[2223]

Superior results of WOG as compared to PTN may be due to the following:

Reciprocating single-file systems extrude fewer bacteria apically than the conventional multifile rotary system[16]

In WOG, each file has a fixed taper from D1–D3, and a progressively decreasing taper from D4–D16, which serves to preserve dentin and also provides space for more debris to auger out[20]

PTN X1 has a square cross-section in the last 3-mm segment and lacks offset design, thus more chances of debris extrusion[24]

WOG is a single-file system unlike PTN; requiring minimum instrumentation and hence less extrusion of debris.[25]

The limitations of the present study are:

The subjective nature of symptoms which are difficult to quantify

The frequency and quantity of analgesics taken and their effect on postinstrumentation pain have not been considered, which may be considered for the future research.

CONCLUSIONS

Within the limitations of this study, it may be concluded that SAF system causes minimum postinstrumentation pain when compared to WOG and PTN, thus emphasizing the suitable instrument selection for cases with symptomatic irreversible pulpitis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.