Influence of three Ni-Ti cleaning and shaping files on postinstrumentation endodontic pain: A triple-blinded, randomized, controlled trial.

AIM: This randomized, controlled trial evaluated the incidence of postinstrumentation pain on using two different rotary Ni-Ti and one reciprocating Ni-Ti cleaning and shaping systems.
MATERIALS AND METHODS: Asfter sample size estimation, a total of 152 patients were randomized to three groups (Group WO [WaveOne], Group PU [ProTaper Universal], and Group Mt [Mtwo]). Selection of patients was based on root curvature, periapical lesion, vitality, gender, and diagnosis of the patient. A similar clinical protocol was followed and endodontic treatment was performed. Pre- and post-instrumentation pain scores (2, 4, 6, 8, 12, 36, and 48 h) were recorded using visual analog scale score. Kruskal-Wallis test was done for overall comparison of the groups. Bonferroni-corrected Mann-Whitney test was done for pair-wise comparisons and Friedman test was done to compare pain between time points in each file system (P < 0.05).
RESULTS: All preinstrumentation pain values were higher than postinstrumentation pain values (P < 0.05). At 48 h, patients in Group WO experienced more pain compared to the other two groups. Pain scores of nonvital teeth were significantly higher when compared to vital teeth. Among nonvital teeth, patients in Group WO had early onset of pain at 6 h and lasted till 48 h, whereas pain started at 12 h and lasted till 36 and 48 h for Group Mt and Group PU, respectively.
CONCLUSION: Patients treated with WaveOne files experienced more pain when compared to the other files. Nonvital teeth experienced more pain compared to vital teeth. Group Mt had the lowest postinstrumentation pain.

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

The primary objective of cleaning and shaping is to debride the intraradicular contents and render the space suitable for obturation. During this process, irritation to the periapex is inevitable, thus causing postinstrumentation pain. In endodontics, postoperative pain is defined as pain of any degree that occurs after initiation of root canal therapy.[1] Although the success of endodontic treatment is highly related to the elimination or reduction of postendodontic pain, many clinical studies have reported varying degrees of postoperative pain, ranging from 25% to 40%.[234] Even though microorganisms are usually regarded as the most common cause of postoperative pain, other causes include mechanical or chemical injury to the periradicular tissues.[2345] During root canal preparation, irrigants, dentin chips, pulp tissue, and microorganisms may get extruded into the periradicular tissues, triggering an acute inflammatory reaction. This leads to the release of chemical mediators and changes in local adaptation and periapical tissue pressure causing postoperative pain. Studies evaluating the apical extrusion of debris have stated that instrumentation techniques and instruments used are the main contributing factor associated with the extrusion of debris.[678]

Reciprocating file systems were developed as a single file system with M-wire technology which uses a reciprocating motion to cut and proceed into the root canal. Data on reciprocating files proved that these files have a better resistance to file separation and less incidence of dentinal damage.[910] Studies on debris extrusion using reciprocating and rotary files are controversial. Variability has been observed between different rotary systems in terms of debris extrusion which can be due to differences in cross-sectional geometry, cutting blade design, taper, flute depth, tip, and sequence of files, kinematics, and cutting efficacy.[11] Furthermore, it has previously been suggested that the reciprocating movement per se might play a role in packing the debris into the irregularities of the root canal space, pushing them beyond the apical foramen.[12] Different Ni–Ti rotary systems may yield different patterns of neurogenic inflammation response in the periodontal ligament as a consequence of different amounts of irritant extruded from the root canal space. However, the threshold amount of debris required for inducing pain in a patient is unknown. On literature search, there is a lack of clinical evidence comparing the postoperative pain after using different Ni–Ti systems employing varied file design and motion kinematics (WaveOne, ProTaper, and Mtwo). The objective of this study was to understand the influence of different motion kinematics on postinstrumentation pain. The null hypothesis of this study was that there was no difference in postinstrumentation pain after using any file systems. Hence, the aim of this study was to compare the postinstrumentation pain following the use of WaveOne, ProTaper, and Mtwo Ni–Ti files.

MATERIALS AND METHODS

This study was intended according to the revised Consolidated Standards of Reporting Trials statement.[13] The study protocol was approved by the Ethics in Clinical Research Committee of Meenakshi University, Chennai, India (Ref no: MADC/IRB/2014/000). A pilot study was done to obtain estimates for sample size calculation. The sample size was calculated as 49 in each group (allocation ratio 1:1:1) using G * power 3.1.2 software (SPSS version 0.17; SPSS Inc., Chicago, IL, USA) with alpha error left at 5% and statistical power of 80% with a dropout rate of 10% in each group. A total of 183 patients were screened for selection criteria in the dental outpatient unit at the Department of Conservative Dentistry and Endodontics, Meenakshi Ammal Dental College and Hospitals. Patients aged between 18 and 55, diagnosed of asymptomatic irreversible pulpitis, symptomatic irreversible pulpitis, or pulp necrosis with or without apical periodontitis (acute or chronic) in premolars and molars with fully matured roots were enrolled in this study. Curved root canals of more than 25°, calcified root canals, periapical radiolucency of more than 2 mm, complex root canal morphology, teeth with abscess/cellulitis, and medically compromised patients were excluded from the study. Pulp vitality was diagnosed using thermal tests and electronic pulp tester (Parkell, Edgewood, NY, USA). The extent and dimensions of periapical radiolucency (paralleling technique) were assessed along the greatest diameter using Schick CDR Software (Sirona, Long Island city, NY, USA). Measurements were performed in triplicate to avoid bias. The level of pre- and post-instrumentation pain was recorded as a continuous data using simple visual analog scale (VAS) scoring. The VAS consisted of a line of 10 cm length anchored by two extremes with 0 cm signifying no pain and 10 cm representing the worst pain imaginable. Patients who experienced a preinstrumentation pain score of more than 6 cm were excluded from this trial.

Consent forms were obtained from all patients. Baseline parameters such as age, gender, vitality status of the tooth, and preinstrumentation pain scores were recorded prior to treatment. The design used in this study was a randomized, triple-blinded, triple arm parallel trial. Stratification and randomization designs were used to address confounding factors. The confounding factors identified in the study were vitality status and the presence of lesion. Computer generated randomization sequence was carried out by the statistician who was not involved in the study. Bias in the trial was further reduced by masking the patients and the outcome assessmentor to the intervention. Parallel groups included Group WO (WaveOne; Dentsply Maillefer, Ballaigues, Switzerland), Group PU (ProTaper Universal; Dentsply Maillefer, Ballaigues, Switzerland), and Group Mt (Mtwo; VDW, Munich, Germany) where the new intervention was Group WO. The randomized order of interventions with Ni–Ti files was concealed in opaque individual envelopes by the staff nurse, which were later opened by the operator at the time of endodontic treatment. The principal investigator, patients, and outcome assessmentor were blinded to the study.

Root canal procedure

Root canal procedure was done for patients under local anesthetic administration (lidocaine hydrochloride and epinephrine 1:80,000; Xilonibsa, Inibsa, Spain) and rubber dam isolation. Access cavity was prepared and working length was determined with Root ZX apex locator (J Morita Europe GVBH, Frankfurt, Germany) and confirmed with digital radiographs. Apical patency and glide path were maintained in all the cases with a 10 size K file (Mani, Utsunomiya, Tochigi, Japan). Cleaning and shaping in Group WO were done with WaveOne primary or large reciprocating file as a single file system. ProTaper rotary files and Mtwo rotary files were used in a sequential order until master apical file in Group PU and Group Mt, respectively. Irrigation with 5% NaOCl was performed using a side vented needle (Maxi-I-probe; Dentsply, Tulsa, OK, USA), at 1 mm short of working length between each file. Based on the initial apical binding files, the master apical file ranged from ISO sizes #20 to #30 in narrow canals and from ISO sizes #30 to #40 in wide canals. Ethylenediaminetetraacetic acid (17%) solution was used for smear layer clearance. A final flush with 2% chlorhexidine solution was performed. Calcium hydroxide (Ca[OH]2) was given as an intracanal medicament for all the patients and temporized with Cavit (3M Deutschland GmbH, Neuss-Germany). The treated tooth was relieved from occlusion. The patients were treated by 4 final year postgraduate students who are calibrated and trained to use different shaping systems.

All patients were prescribed ibuprofen 400 mg as an escape medicine in the event of severe pain. The patients were contacted through phone calls by the outcome assessor and the VAS scoring was recorded at 2, 4, 6, 12, 24, 36, and 48 h, respectively.

Statistical analysis

Nonparametric statistical analysis was planned in this study. Kruskal–Wallis test was done for overall comparison of three file systems. Bonferroni-corrected Mann–Whitney test was performed for pairwise comparison. Friedman test was done to compare between time points in each file system. Data were analyzed using the SPSS 17.0 for Windows (SPSS Inc., Chicago, IL, USA) statistical package. Subgroup analysis for independent variables (sex, vitality status, and presence of lesion) was done using Bonferroni-corrected Mann–Whitney test (P < 0.05). Relative risk (RR) of experiencing pain postinstrumentation was calculated for 12, 24, and 48 h.

RESULTS

A total of 183 patients were screened, out of which 31 patients did not meet the inclusion criteria and 152 patients participated in the study [Figure 1]. The study was conducted from September 2013 to June 2014. Statistical analysis of baseline parameters had no significant difference among them [Table 1]. The overall incidence of postinstrumentation pain at various time periods is shown in Table 2. The postinstrumentation pain values were lower than preinstrumentation values and the difference was statistically significant (P < 0.05). The postinstrumentation pain values remained insignificant at different time points within the same group. There was no statistically significant difference in postinstrumentation pain between groups with regards to gender. The pain scores at 48 h were significantly higher in Group WO when compared to Group Mt and PU (P < 0.05). There was no statistical difference between Group Mt and PU at 48 h. Pulp vitality was not a significant factor leading to pain at the end of 2 and 4 h between groups. However, there was a significant difference in pain between vital and nonvital pulp status at 6 h and the same trend continued till 48 h, irrespective of file systems used (P < 0.05). Pain scores of nonvital tooth in Group WO had comparatively high pain value that started at 6 h and continued till 48 h, whereas the pain scores of nonvital teeth in Group PU and Mt started at 12 h and lasted till 48 h and 36 h, respectively (P < 0.05). The RR of developing postinstrumentation pain was higher with WaveOne when compared to Mtwo (RR = 1.8 95% CI 1.3–2.7) and ProTaper (RR = 1.7 95% CI 1.2–2.5) at the end of 48 h [Table 3].

Figure 1

A Consolidated Standards of Reporting Trial diagram showing the flow of participants through each stage of trial

Table 1

Preendodontic baseline parameters

Table 2

Overall incidence of postinstrumentation pain at different time intervals

Table 3

The relative risk of developing postinstrumentation pain at different time intervals for the groups studied

DISCUSSION

The success of endodontic therapy depends not merely on their efficacy and proper completion but also on minimal patient discomfort. In recent decades, the discussion on reciprocating file systems has gained attention. Few in-vitro studies proved that the extrusion of debris is more with reciprocating files when compared to continuous rotary files. However, no attempt was made to simulate the presence of vital pulp or periapical tissues when determining the debris extrusion.[1415] Results could change in a clinical situation because of the presence of periapical tissues, which act as a natural barrier to prevent debris extrusion. Hence, this study compared the postinstrumentation pain on using two different rotary file systems (ProTaper, Mtwo) and one reciprocating file system (WaveOne). This study rejects the null hypothesis and has shown that there is a difference of pain values among the groups.

WaveOne reciprocating files were selected for this trial as a new intervention to evaluate the influence of motion kinematics for reduction of postinstrumentation pain. ProTaper was selected in this study to assess the influence of variable taper along the length of the file in causing postinstrumentation discomfort. Mtwo has been proved to have a better cyclic fatigue resistance, shaping ability in curved root canals, and less debris extrusion when compared to other conventional Ni–Ti files.[161718] On literature search, WaveOne rotary files extruded more debris when compared to other continuous rotary files in in-vitro studies.[14] However, the clinical data on reciprocating systems does not compare this file system with constant taper files.[19] Moreover, the published data on postoperative pain using WaveOne reciprocating files were recorded following endodontic treatment in a single visit. This could confound the effect of obturation on posttreament pain.[202122]

Neglecting apical patency may cause risk of loss of length, canal transportation, other accidents such as ledges and improper irrigation and disinfection in the apical third of the canal.[23] Arias et al. compared the incidence of postoperative pain with or without apical patency and reported that the apical patency has no role in postoperative pain.[24] A similar finding was observed with the extent of foraminal enlargement.[25] Hence, apical patency was maintained with K 10# file in all the patients to ensure disinfection of apical one-third.

Irrigation technique was thought as a potential confounder. Concomitantly, side-vented needles have shown to cause minimal debris extrusion and hence employed in this study.[6] Ca[OH]2 was given as an intracanal medicament for all cases irrespective of vitality status. Dispute may arise on specific recommendations on using Ca[OH]2 in vital or nonvital cases. Walton et al. have reported that the use of Ca[OH]2 as an intracanal medication was unrelated to the incidence and/or severity of posttreatment pain.[26]

Pain perception is purely subjective depending on patient's threshold and variable experience modulated by multiple physical and psychological factors. In the current study, simple VAS was used as a result of its ease, valid, and reliable scale to measure pain.[27]

Statistical analysis of the baseline parameter showed no significant difference among the groups, thus confirming equal and homogeneous distribution of the samples among the three groups (successful randomization). The principal investigator, outcome assessor, and the patients were blinded in this clinical trial. The operators were not blinded in this trial but were not aware of the instrumentation system until the moment of cleaning and shaping (allocation concealment). This step helped to reduce operator-dependent variations.

Gender has been suggested to play a role in other pain studies. In the endodontic literature, females have shown to experience higher levels of postoperative pain compared to males.[28] However, in our study, gender did not play a role in postinstrumentation pain.

The results of this study showed a significant reduction in postinstrumentation pain score values when compared to preoperative pain values irrespective of file system used. This concept is supported by many previous studies proving that endodontic procedure of a diseased tooth helps in alleviation of symptomatic pulpitis.[29] At 48 h, patients in Group WO experienced more discomfort when compared to patients in Group Mt followed by Group PU. The risk of developing postinstrumentation pain was almost twice with WaveOne file system compared to other two file systems. The possible reasons for the debris extrusion may be due to the cross-sectional geometry of the file, instrumentation technique, motion of the file, irrigation system, or anatomy of the root. The latter two confounders were eliminated by randomization. ProTaper and WaveOne files are characterized by a triangular or modified triangular cross-section resulting in a lower cutting efficiency with smaller chip space. This design may enhance debris transportation toward the apex when used in combination with a reciprocal motion.[12] ProTaper and WaveOne systems have a similar file cross-section; however, patients in Group WO experienced more pain compared to Group PU. The difference in motion of kinematics between the two file systems could be the underlying reason.

On comparison of teeth with regards to vitality, nonvital teeth experienced more pain compared to vital teeth across all groups. Extrusion of infected pulp tissue has shown to trigger an acute inflammatory response.[30] Moreover, the direct interaction of extruded bacteria and host cells can result in postinstrumentation pain. At 2 and 4 h, there was no statistical difference among nonvital and vital tooth in all groups. The lack of pain initially could be attributed to the influence of anesthesia. For nonvital teeth, among the three experimental groups, patients in WO Group experienced early onset of pain at 6 h and lasted until 48 h implying that this file system can complicate postinstrumentation pain. Patients with nonvital teeth in Group Mt and Group PU had the onset of pain at 12 h and lasted up to 36 and 48 h, respectively. Patients with nonvital teeth in Group Mt experienced lesser pain following instrumentation as compared to other groups. Even though the influence of several factors was studied in this trial, multivariate comparison was not possible due to insignificant odd's ratio for a majority of factors.

The results of the study can be extrapolated to posterior teeth with mild to moderately curved canals and in the absence periapical lesion. The influence of root canals with curvature >25 degrees, effect on anterior teeth, and presence of periapical lesion needs be explored in future trials.

CONCLUSIONS

Under the limitations of this study, it can be concluded that WaveOne reciprocating files cause more postinstrumentation pain followed by ProTaper and Mtwo. Caution should be exercised on instrument selection for appropriate cases such as nonvital pulp with curved root canals.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.