Reciprocating kinematics leads to lower incidences of postoperative pain than rotary kinematics after endodontic treatment: A systematic review and meta-analysis of randomized controlled trial.

BACKGROUND: Extrusion of infected debris into the periapical tissue has been cited as the major cause of postoperative pain, regardless of instrumentation technique. AIM: Comprehensively review two different kinematics of instrumentation (reciprocating and rotary) and association to the postoperative pain after endodontic treatment.
METHODS: Two investigators performed a systematic review with meta-analysis. MEDLINE/PubMed, Cochrane Library, and Scopus supplied relevant data from studies published until February 2018 to answer the PICO question. Primary outcome was overall postoperative pain, and the secondary outcomes were nature of the pain (mild, moderate, and severe) at 12, 24, and 48 h.
RESULTS: Ten randomized clinical trials fulfilled eligibility criteria, and five of them were submitted in the meta-analysis. Primary outcome indicated that reciprocating system results in less postoperative pain compared to rotary system (P < 0.05). As a secondary outcome, there was no statistical difference for mild, moderate, and severe pain after 12 and 24 h using reciprocating or rotary systems (P > 0.05). However, the reciprocation system showed less severe pain after 48 h (P < 0.05).
CONCLUSION: Rotary motion had a negative impact on postoperative pain after endodontic treatment. Furthermore, after 48 h, more patients presented severe pain under rotary motion. More randomized clinical studies would be helpful. Copyright:

INTRODUCTION

Endodontic treatment is a conservative way of treating teeth with pulpal disease. Due to recent advances in dental treatment modalities, patients are constantly being challenged to choose between root canal treatments and implant placement.[1]

Although root canal therapy should be the treatment of choice over implant placement in teeth with favorable prognosis, the presence of postoperative pain could pose as an unfavorable outcome. In a systematic review, Sathorn et al.[2] reported a prevalence rate ranging from 3% to 58% for pain after root canal treatment, corroborating with recent studies.[34]

Furthermore, studies have reported intensity standards of postoperative pain as mild, moderate, and severe.[56789] The highest postoperative pain level is recorded in the early stages post root canal treatment – up to 12 h – and this might be attributed to the ongoing inflammatory process. The prevalence and severity of pain substantially decrease within the first 48 h.[67910]

Several etiologic factors are attributed to this postoperative pain such as history of preoperative pain, insufficient root canal debridement, hyperocclusion, periapical disease, and extrusion of infected debris into the periapical tissue. The last has been cited as the major cause of pain after endodontic treatment.[1112] Every endodontic instrumentation technique available can produce apical extrusion of debris during chemomechanical preparation of the root canals, even when short of the apical foramen.[2] It can be stated that extrusion of debris is an inevitable occurrence that could be reduced using accurate irrigation and aspiration techniques, instrumentation limited to the confines of the canal, and use of different endodontic files and their kinematics.[131415161718]

The first rotary Nickel–Titanium (NiTi) instrument was placed on the market in 1992, and since then, its refinement can be noted through the use of new technologies such as reduced number of files and heat treatments which therefore resulted in improvements on the file quality and resistance. Those changes led to the emerging of the reciprocating files, which have a different motion that relieves the stress on the instrument by special counterclockwise and clockwise movements.[19] Research findings comparing rotary and reciprocating systems have reported a decrease in preparation time and increase in cyclic fatigue in reciprocating files, while keeping similar shaping ability to rotary systems.[20]

Some studies have shown that the prevalence of pain after endodontic treatment is greater when using rotary instrumentation with multiple instruments.[59] On the other hand, there are several studies reporting the decrease of postoperative pain using reciprocating systems.[182122] These findings could be attributed to differences in systems, regarding to the cross-section, cutting-edge design, taper, tip type, configuration, flexibility, alloy type, number of files used, kinematics, or cutting efficacy.[579182122] In addition, the singularity, personality, and operator training can also influence the extrusion of debris in periapical area contributing to the pain outcome.[579182122] Some recent studies have reported no significant difference in postoperative pain between rotary and reciprocating systems, and therefore, instrumentation kinematics had no impact on intensity of postoperative pain.[681023]

A systematic review and meta-analysis was performed by Caviedes-Bucheli at al.[24] in 2015 regarding the influence of reciprocating and rotary files on the apical extrusion of debris and its biological relationship with symptomatic apical periodontitis. They concluded that both rotary and reciprocating systems generate apical extrusion of debris and expression of neuropeptides. The authors included and evaluated in vitro and clinical studies and supported the fact that the inflammatory reaction is not influenced by the number of files but by the type of movement (reciprocating movement) and the instrument design (triangular cross-sectional design).

Recently, Hou et al.[25] published a systematic review and meta-analysis considering postendodontic pain following root canal preparation with rotary versus reciprocating instruments. Three studies were included, and the conclusion was that rotary instruments were associated with a lower incidence of postoperative pain after endodontic treatment when compared to reciprocating instruments, while reciprocating instruments were associated with less mild postoperative pain incidence. However, since then, several randomized clinical trials have been published driving the need of a new systematic review.

In summary, clinicians who read the published literature hoping to have their questions answered regarding to the appropriate technique to adopt in treating teeth with potential for postoperative pain will find conflicting results. Certainly, current literature does not contain a clear guide toward choosing a correct kinematic system on automated endodontic treatment to prevent postoperative pain.

Thus, the purpose of this systematic review was to comprehensively review two different kinematics of instrumentation (reciprocating and rotary) regarding to the postoperative pain after endodontic treatment. Null hypothesis was that there would be no difference in postoperative pain between the tested kinematics.

METHODS

Protocol and registration

This article was designed according to the Cochrane criteria (Cochrane Handbook for Systematic Reviews of Interventions, version 5.1.0)[26] for elaborating a systematic review and meta-analysis and adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement.[27] The study was registered at the International Prospective Register of Systematic Reviews (PROSPERO-CRD42017077490).

Eligibility criteria

The inclusion criteria were: (1) randomized controlled trials, (2) studies that evaluated reciprocating versus rotary system for root canal treatment, (3) studies that evaluated postoperative pain, and (4) studies published in English language. Exclusion criteria included any articles that failed to meet the inclusion criteria and studies that evaluated root canal retreatment.

A specific clinical question was structured according to the PICO approach: the addressed focus question was: does the endodontic treatment using reciprocating system cause more pain than using the rotary system? In this process, (P) represents teeth endodontically treated with (I) reciprocating system, (C) compared to rotary system and (O) the primary outcome to be extracted and analyzed in the meta-analysis was the overall postoperative pain. The postoperative pain after 12, 24, and 48 h was the secondary outcome.

Information sources

An electronic search in the PubMed/MEDLINE, Cochrane Library, and Scopus databases was conducted until August 2018. Furthermore, a manual search was conducted to identify gray literature and registered trials not yet published until 2018 from the following journals: Journal of Dental Research, Journal of Endodontics, International Endodontic Journal, PLOS ONE, Journal of Dentistry, Clinical Oral Investigations, International Journal of Oral Science, Oral Surgery, Oral Medicine, Oral Pathology, and Oral Radiology.

Search

Two independent researchers (C.M.M and A.C.A.S) performed the electronic search at the selected databases. The search terms used were: (1) clinical trial and reciprocating and rotary and endodontic, (2) reciprocating and rotary and endodontic, (3) reciprocating and endodontic, and (4) rotary and endodontic.

Study selection

Two researchers (C.M.M. and A.C.A.S.) independently selected the studies according to their titles and abstracts and categorized them as included or excluded. Any disagreements were settled through discussion and consensus with a third researcher (V.E.S.B.). After that, both investigators read the articles selected for inclusion, and a manual search was performed on the reference list.

Data collection process and data items

Subsequently, the full-text of the obtained articles was analyzed. The analysis of these selected articles was used to answer the PICO questions. The researcher (C.M.M.) collected relevant information from the articles, including author, year, study type, number of patient and teeth sample size, gender, age average, teeth with necrosis, teeth with vital pulp, number of visit, number of teeth treated with reciprocation system, number of teeth treated with rotatory system, irrigating solution type, use of ultrasonic, brand of endodontic fill cement, obturation method and temporary restoration, methods of analysis of pain, pain control, follow-up, and pain outcome. Then, a second researcher (V.E.S.B.) checked all of the collected information. A fourth researcher (A.C.A.) settled any disagreement between the investigators through discussion until a consensus was obtained. Duplicate subject publications within separate unique studies were not reported twice.

Risk of bias

The risk of bias assessment in the included studies was evaluated using the Cochrane Collaboration's Tool for Assessing Risk of Bias in Randomized Trials.[26] The assessment criteria is a domain-based evaluation in which critical assessments are made separately for different domains: random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective reporting, and other bias.[26] For each domain, the risk of bias was graded as high, low, or unclear based on criteria described in the Cochrane Handbook for Systematic reviews of Interventions 5.1.0.[26]

Summary measures

The meta-analysis was based on the Mantel-Haenszel method.[28] Overall postoperative pain was the dichotomous outcome measure that was evaluated. To assess the postoperative pain, the statistical unit for the outcome was the number of patients who attribute a value to their perceived pain based on the visual analog scale (VAS) by the presence or absence of pain. Accordingly, risk ratio (RR) and corresponding 95% confidence intervals (CI) using a random-effects model were applied to the recent studies.[2930] The RR values were considered significant when P < 0.05. To perform the meta-analysis and the funnel plot it was used the software Reviewer Manager 5 (Cochrane Group).

Bias risk among the studies

An asymmetric funnel plot may indicate publication bias or other biases related to sample size, although the asymmetry may also show a true relationship between trial size and effect size.[31] The heterogeneity was assessed using the Q method (χ2) and the value of I2.[32] The outcomes were dichotomized into good and poor results. The I2 values above 75 (range 0–100) were considered to indicate significant heterogeneity.[32]

Additional analysis

To analyze the sensitivity of the tests employed, a subgroup analysis was performed to identify any potential causes of heterogeneity. Specifically, the subgroups considered were (1) the nature of pain (mild, moderate, and severe pain) after 12 h, (2) 24 h, and (3) 48 h. The nature of postoperative pain was categorized since each protocol can cause more pain than the other. Postoperative pain is more common in the early hours, up to 12 hours, having the tendency to decrease over days (24 and 48 hours).

The kappa statistic was calculated to define the inter-reader agreement in the study selection process. According to Landis and Koch,[33] the level of inter-reader agreement is almost perfect if the value of Kappa (κ) is 0.81–1.00, substantial if κ is 0.61–0.80, moderate if κ is 0.41–0.60, fair if κ is 0.21–0.40, and poor if κ is < 0.20.

RESULTS

A total of 983 articles were retrieved, of which only 10 fulfilled eligibility criteria (inter-reader agreement, κ =0.8 for PubMed/Medline, κ =1 for Cochrane Library, and κ =1 for Scopus) [Figure 1]. All the studies selected were randomized clinical trials and compared the postoperative pain after using reciprocating and rotary endodontic systems.[567891018212223] The risk of bias assessment of the included studies is described in Table 1. Extracted data are summarized in Table 2.

Figure 1

Diagram of the literature search

Table 1

Risk of bias among the studies

	Random sequence generation (selection bias)	Allocation concealment (selection bias)	Blinding of participants and personnel (performance bias)	Blinding of outcome assessment (detection bias)	Incomplete outcome data addressed (attrition bias)	Selective reporting (reporting bias)	Other bias
Pasqualini et al., 2015	+	+	+	+	+	+	+
Nekoofar et al., 2015	+	+	+	?	+	+	+
Neelakantan et al., 2015	+	+	+	?	+	+	+
Revas et al., 2016	+	+	+	+	+	+	+
Kherlakian et al., 2016	+	+	+	?	+	+	+
ÇiÇek et al., 2016	+	-	+	+	+	+	+
Krithikadatta et al., 2016	+	+	+	+	?	+	+
Zand et al., 2016	+	+	+	+	+	+	+
Mollashahi et al., 2017	+	-	+	+	+	+	+
Shokraneh et al., 2017	+	-	+	+	+	+	+

+: Low risk of bias, ?: Unclear risk of bias, -: High risk of bias

Table 2

Articles included in the systematic review

Author/Year	Initial patientes/teeth sample size	Final patientes/teeth sample size	Gender	Age range/average	Necrosis	Vital Pulp	N of Visit	Reciprocation System/Initial Size/After Drop Out	Rotary System/Initial Size/After Drop Out	Irrigating Solution	Endodontic fill cement	Obturation Method/Temporary sealing	Pain control	Pain analysis	Pain Outcome
Neelakantan et al., 2015	624/1248	605/1210	F and M	25-40/31	-	1210	Single	Reciproc/ 624/605	OneShape /624/605	3% NaOCl, EDTA Gel as lubrificant for glidepath; Final irrigation: 17% EDTA + 3% NaOCl + Saline Solution and Ultrasonic	MTA Plus Sealer	Lateral condensation/Glass Ionomer Cement	Ibuprofen 400mg, if necessary	Every day until 7 days	The use of Reciproc instrumentation system showed significantly less intensity posttreatment pain compared to the single-file rotary system (One Shape) in patients with symptomatic irreversible pulpitis with apical periodontitis. Rotary motion had a negative impact on immediate postoperative discomfort.
Nekoofar et al., 2015	42/42	42/42	F and M	15-55/35	-	42	Two visit/No intracanal medication	WaveOne/21/21	ProTaper/21/21	2% Chlorhexidine; Final irrigation using 17% EDTA (protocol unclear)	AH 26 Sealer	Lateral condensation/Reinforced Zinc Oxide-Eugenol	Single dose of 400 mg ibuprofen tablet and continue the use if necessary	6, 12, 18, 24, 48 and 72h	Postoperative pain lasted longer and was more intense in patients treated with the WaveOne syspem compared to ProTaper Universal. However, the differences seen in the intensity of pain may not be clinically significant and did not affect the analgesic regime chosen by patients. Reciprocating motion had a negative impact on immediate postoperative discomfort.
Pasqualini et al., 2015	52/52	47/47	F and M	16-60/38	20	32	Single	WaveOne/26/24	ProTaper/26/23	5% NaOCl and 10% EDTA (protocol unclear)	Pulp Canal Sealer	Continuous wave of condensation technique/IRM	Unclear, optional analgesic if necessary	Every day until 7 days	Reciprocating system caused maximum pain values compared with rotary system. Reciprocating motion had a negative impact on immediate postoperative discomfort.
Çiçek et al., 2016	90/90	60/60	F and M	21-65/37	60	-	Single	WaveOne/30/30	ProTaper Next/30/30	5.25% NaOCl; Final irrigation: 17% EDTA + Chlorhexidine + Distiled Water	AH 26 Sealer	Lateral condensation/Dental adhesive and composite resin	Unclear	12, 24 and 48h	No significant difference in postoperative pain between ProTaper Next and Wave One groups under experimental time. Instrumentation kinematics had no impact on intensity of postoperative pain.
Kherlakian et al., 2016	210/210	210/210	F and M	19-73/47	-	210	Single	Group 1: WaveOne/70/70 Group 2: Reciproc/70/70	ProTaper Next/70/70	2.5% NaOCl; Final irrigation: 17% EDTA + 2.5% NaOCl + Saline Solution and Ultrasonic	AH Plus Sealer	Continuous wave of condensation technique/Dentinal Adhesive and Composite Resin	Ibuprofen 400mg, if necessary	24, 48, 72h and 7 days	No significant difference in postoperative pain between ProTaper Next, Reciproc and WaveOne groups under experimental time. Instrumentation kinematics had no impact on the intensity of postoperative pain.
Krithikadatta et al., 2016	152/152*	147/147	F and M	18-55/36.5	33	114	Two visit/Intracanal medication with Calcium Hidroxide	WaveOne/49/49*	Group 1: ProTaper/49/49 Group 2: Mtwo/49/49*	5% NaOCl; Final irrigation: 17% EDTA and 2% Chlorhexidine	Teeth were not obtured	Teeth were not obtured, was temporary sealed with Cavit	Ibuprofen 400mg, if necessary	2, 4, 6, 8, 12, 36 and 48h	WaveOne reciprocating files cause more postinstrumentation pain followed by ProTaper and MTwo. Reciprocating motion had a negative impact on immediate postoperative discomfort.
Relvas et al., 2016	78/78	78/78	M	18-64/41	78	-	Single	Reciproc/39/39	ProTaper/39/39	2.5% NaOCl; Final irrigation: 17% EDTA + 2.5% NaOCl	AH Plus Sealer	Single cone + thermomechanical compaction method with #60 McSpadden/Glass Ionomer Cement	Unclear	24, 72 and 7 days	No significant difference in postoperative pain between ProTaper and Reciproc groups under experimental time. Instrumentation kinematics had no impact on the intensity of postoperative pain.
Zand et al., 2016	90/90	90/90	F and M	19-59/33.5	90	-	Single	Reciproc/45/45	RaCe/45/45	17% EDTA gel-form + Saline Solution; Final irrigation: 2.5% NaOCl + saline solution	AH 26 Sealer	Lateral condensation/Temporary filling material	Unclear	4, 12, 24, 48, 72h and 7 days	RaCe Rotary systems, resulted in less severe postoperative pain compared to the Reciproc files. Reciprocating motion had a negative impact on immediate postoperative discomfort.
Mollashahi et al., 2017	160/160*	100/100	F and M	20-50/31.7	-	150	Single	Reciproc/50/50*	OneShape /50/50*	2.5% NaOCl; Final irrigation: 17% EDTA + 2.5% NaOCl + Saline Solution and Ultrasonic	AH-26 Sealer	Lateral condensation/Cavit	Ibuprofen 400mg, if necessary	6, 12, 24, 48 and 72h	No significant difference in postoperative pain between OneShape and Reciproc groups under experimental time. Instrumentation kinematics had no impact on intensity of postoperative pain.
Shokraneh et al., 2017	96/96	63/63	F and M	20-45/32.5	93	-	Single	WaveOne/32/32	ProTaper/32/31	5.25% NaOCl; Final irrigation: 17% EDTA + Saline Solution	AH 26 Sealer	Lateral condensation/Cavit	Single dose of 400 mg ibuprofen tablet	6, 12, 28, 24, 48 and 72h	WaveOne system caused lower postoperative pain levels at 6, 12, and 18 h compared with ProTaper group, but at 24, 48 and 72 hours no significant difference in postoperative pain between ProTaper and Reciproc groups. Totary kinematic had a negative impact on immediate postoperative pain

For the first selection, three articles were selected and subsequently excluded. Gomes et al., 2017,[34] evaluated intraoperative pain, and the goal of this present work was to evaluate the postoperative pain. Arslan et al., 2016,[35] evaluated various kinematic movements on postoperative pain using only the Reciproc (VDW, Germany) system. Gambarini et al., 2013,[36] performed a research to evaluate and compare postoperative pain using three different NiTi instrumentation techniques; however, this was not a randomized clinical trial.

Study characteristics

A total of 1442 patients, regardless of gender, with an average age of 36.3 years had 2047 teeth treated endodontically. From this, 1035 teeth were treated with reciprocation system and 1012 teeth were treated with rotary system. The reciprocation systems used were WaveOne (Dentsply Maillefer, Switzerland)[679102122] and Reciproc (VDW, Germany),[58101823] and the rotary systems used were OneShape (MicroMega, France),[523] ProTaper (Dentsply Maillefer, Switzerland)[7892122] ProTaper Next (Dentsply Maillefer, Switzerland),[610] Mtwo (VDW, Germany),[7] and RaCe.[18] Protocols were used according to manufacturer recommendations for the determination of file size and instrumentation techniques.

Vital pulp was diagnosed in 1758 teeth, and 374 teeth were diagnosed with pulp necrosis with the presence or absence of periapical lesion. Only four studies performed endodontic treatment in teeth diagnosed with vital pulp.[5102123] Likewise, only four studies performed endodontic treatment in teeth with pulp necrosis.[68918] Only 2 studies evaluated the postoperative pain in both pulp conditions.[722]

The endodontic treatment was completed in a single visit in all studies except 2 clinical trials that performed two-visit endodontic treatment. Nekoofar et al., 2015, study consisted of a two-visit endodontic treatment, although they did not use any dressing between appointments. Likewise, Krithikadatta et al., 2016, also performed a root canal treatment in two visits but with the use of intracanal medication with calcium hydroxide. They analyzed pain by VAS after cleaning and shaping of the root canal system and the use of intracanal medication before and after the obturation.

During chemical mechanical preparation, different irrigating solutions were used. Sodium hypochlorite (NaOCl) was the irrigant of choice in 6 articles, with concentrations ranging from 2.5% to 5.25%.[67891023] Neelakantan et al., 2015, used 3% NaOCl associated with ethylenediaminetetraacetic acid (EDTA) gel-form as lubricant for glidepath. Pasqualini et al., 2015, used an association of 5% NaOCl and 10% EDTA. Nekoofar et al., 2015 used 2% Chlorhexidine as an irrigating solution and Zand et al., 2016 used 17% EDTA gel-form associated with saline solution.

As a final rinse, 8 researches used EDTA followed by its irrigating solution, distilled water, saline solution or even chlorhexidine.[56789102123] Zand et al., 2016 used EDTA as an irrigating solution, so they used NaOCl associated with saline solution as a final irrigant. Three studies reported the use of ultrasonic during the irrigation steps.[51023]

For obturation, the most used cement was AH 26 Sealer and AH Plus Sealer.[68910182123] Additionally, Mineral Trioxide Aggregate Plus Sealer[5] and Pulp Canal Sealer[22] were used. The most common method for obturation was lateral condensation.[569182123] Two clinical trials used continuous wave technique[1022] and one used single cone with thermomechanical compaction through McSpadden.[8]

After completion of the endodontic treatment, Nekoofar et al. 2015 and Shokraneh et al. 2017 prescribed a single dose of 400 mg ibuprofen tablet to their patients and six clinical trials indicated the use of analgesics as needed.[5710212223]

The follow-up was completed mostly using VAS for 1st h until 7 days after endodontic treatment. The main objective was to analyze postoperative pain. As conclusion, four studies have reported more pain using reciprocating system,[7182122] and four studies have reported no difference between the kinematics.[681023]

The main goal and its respective primary outcome is synthetized in Table 3.

Table 3

Summary of each study according to aim of the study and outcome

Author	Year	Aim	Outcome
Neelakantan et al.	2015	Establish the influence of instrumentation technique, using single-file reciprocation or single-file rotary, on posttreatment pain regarding to the incidence, degree, and duration in a prospective multicenter clinical trial	The use of Reciproc instrumentation system showed significantly less intensity and longer duration of moderate and severe posttreatment pain compared to the single-file rotary system (one shape) in patients with symptomatic irreversible pulpitis with apical periodontitis. Although the exact reason for this was not assessed in this study, it may be attributed to the instrumentation kinematics
Nekoofar et al.	2015	Compare the incidence and intensity of postoperative pain after use of the WaveOne reciprocating system and the ProTaper Universal rotary system to prepare root canals in permanent human teeth	Postoperative pain lasted longer and was more intense in patients treated with the WaveOne system compared with the ProTaper Universal system. However, the differences seen in the intensity of pain may not be clinically significant and did not affect the analgesic regime chosen by patients
Pasqualini et al.	2015	Evaluate the impact of ProTaper rotary and WaveOne reciprocating file shaping techniques on immediate patient’s quality of life	Reciprocating motion by WaveOne had an impact on immediate postoperative discomfort, when performed in a single visit and when pre-existing periradicular inflammation was present, thereby negatively influencing patients’ quality of life
Çiçek et al.	2016	Compare the incidence and intensity of postoperative pain related to different root canal instrumentation techniques during single visit root canal treatment using ProTaper Next, WaveOne and Modified Step Back technique	All instrumentation techniques caused postoperative pain. The mean pain scores demonstrated that all techniques produced slight pain that caused mild discomfort and no need for additional treatment. It can be concluded that the modified step back technique can produce less pain compared to the ProTaper Next rotational and WaveOne reciprocal techniques especially in the 48 h period. The effect of instrumentation techniques on the incidence and intensity of postoperative pain should be well-evaluated
Kherlakian et al.	2016	Clinically compare the incidence of postoperative pain after the root canal preparation of posterior teeth using 2 reciprocating systems - Reciproc and WaveOne - and a continuous rotary system - ProTaper Next - through a prospective randomized trial. Analgesic medication intake by patients was also studied	The incidence of postoperative pain and the intake of analgesic medication prescribed for all the postoperative time points were similar across all types of instrumentation systems assessed in this study, the Reciproc, WaveOne and ProTaper Next
Krithikadatta et al.	2016	Compare the postinstrumentation pain following the use of WaveOne, Protaper and Mtwo Ni-Ti files	WaveOne reciprocating files cause more postintrumentation pain followed by Protapper and Mtwo. Caution should be exercised on instrument seletion for appropriate cases such as nonvital pulp with curved root canals
Relvas et al.	2016	Assess postoperative pain in a prospective randomized clinical trial comparing two groups, using the Reciproc system in one group and the ProTaper rotary system in the other. The primary outcome measure of the study was to assess if different instrumentation techniques influence the occurrence of postoperative pain	The different instrumentation techniques, Reciproc and ProTaper did not affect the occurrence of postoperative pain during the time intervals analyzed
Zand et al.	2016	Determine the severity of postoperative pain after using the single-file root canal preparation system with Reciproc system in comparison to preparation with RaCe system using the crown-down technique in necrotic teeth. The results of this study might help choose an appropriate technique for root canal treatment with less postoperative complications and discomfort	Based on the results of the present study; preparing and shaping the root canals in the necrotic mandibular molars with RaCe Rotary systems, resulted in less severe postoperative pain compared to the Reciproc files
Mollashahi et al.	2017	Compare intensity of postoperative pain after the root canal preparation of molars diagnosed with symptomatic irreversible pulpitis using three different instrumentation techniques: hand, single-file rotary (OneShape), and single-file reciprocating (Reciproc) systems	This study found significantly higher levels of postoperative pain in the control group using K-files compared to Reciproc and OneShape groups. No significant difference was found between Reciproc and OneShape groups in terms of pain after endodontic treatment. It seems that the instrumentation kinematics had no impact on intensity of postoperative pain
Shokraneh et al.	2017	Compare postoperative pain in patients with asymptomatic mandibular molar teeth with necrotic pulps and periapical lesions using three different instrumentation techniques: hand, multifile rotary (ProTaper Universal), and reciprocating single-file (Wave-One) instrumentation techniques	In patients with asymptomatic mandibular molar teeth with necrotic pulps and periapical lesions, preparation of the root canal system with the Wave-One reciprocating single-file instrumentation technique resulted in significantly less postoperative pain and needed for analgesic consumption than the multi-file rotary instrumentation technique with ProTaper Universal and hand instrumentation techniques

Meta-analysis

Primary outcome

To answer the PICO question, the primary outcome was performed on the five studies[56789] that reported the presence or absence of pain after endodontic treatment using reciprocating or rotary systems. A weighted average across the studies was provided according to a random-effects model, which indicated that reciprocating system causes absence of pain more often when compared with rotary system (RR: 0.75; 95% CI: 0.62–0.90; P = 0.003). The intrastudy heterogeneity measures were χ2= 2.13. The interstudy heterogeneity measures were I2= 0%. The funnel plot showed an evident symmetry among the differences of means for the studies evaluated, showing absence of bias [Figure 2a].

Figure 2

Forest plot and funnel plot; comparison of rotary and reciprocating system on postoperative pain: (a) Overall; (b-d) according to the nature of postoperative pain - mild, moderate, and severe - after 12 h; (e-g) according to the nature of postoperative pain - mild, moderate, and severe - after 24 h; (h-j) according to the nature of postoperative pain - mild, moderate, and severe - after 48 h

Secondary outcome

A specific analysis for the nature of pain (mild, moderate, and severe pain) after 12 h, 24 h, and 48 h was performed. There was no statistical difference for mild (RR: 0.69; 95% CI: 0.36–1.33; P = 0.27, χ2= 0.02, I2= 0%), moderate (RR: 1.08; 95% CI: 0.51–2.26; P = 0.84, χ2= 3.03, I2= 34%), and severe (RR: 0.69; 95% CI: 0.27–1.76; P = 0.44, χ2= 0.19, I2= 0%) pain after 12 h of endodontic treatment using reciprocating or rotary systems. Furthermore, there was no statistical difference for mild (RR: 1.21; 95% CI: 0.63–2.33; P = 0.57, χ2= 6.90, I2= 57%), moderate (RR: 0.82; 95% CI: 0.65–1.04; P = 0.10, χ2= 2.96, I2= 0%), and severe (RR: 1.03; 95% CI: 0.99–1.07; P = 0.14, χ2= 9.23, I2= 57%) pain after 24 h of endodontic treatment using reciprocating or rotary systems. Finally, there was no statistical difference for mild (RR: 1.64; 95% CI: 0.31–8.84; P = 0.56, χ2= 4.64, I2= 78%) and moderate (RR: 0.46; 95% CI: 0.07–3.14; P = 0.42, χ2= 9.15, I2= 78%) pain after 48 h of endodontic treatment using reciprocation or rotary systems; however, the reciprocating system showed less severe pain (RR: 1.02; 95% CI: 1.01–1.03; P = 0.003, χ2= 0.38, I2= 0%) after 48 h of endodontic treatment compared with rotary systems [Figures 2b–j].

DISCUSSION

Postoperative pain is one of the major unfavorable outcomes after endodontic treatment. This systematic review addressed the influence of two different kinematics, rotary and reciprocating systems, on postoperative pain. It is important to understand that systematic review and meta-analysis concerning randomized clinical trials has a strong relationship with clinical reality. The null hypothesis was that there would be no difference in postoperative pain between the tested kinematics studied. However, after performing the research, the null hypothesis was denied, as rotary motion seems to negatively impact the postoperative pain after root canal treatment.

Overall, rotary motion causes more cases of postoperative pain, regardless of pain intensity and time. Reciprocating motion has been demonstrated to bring about lesser bacterial extrusion compared to multifile rotary systems,[37] and consequently, there is a minor frequency of pain.[38]

Furthermore, most of cases analyzed on meta-analysis were on vital pulp teeth, which were considered to have less extrusion of microorganisms into the periapex since root canal was not massively infected. It is reported in the literature that an asymptomatic necrotic pulp with a periapical lesion is the most likely predisposing clinical condition for the occurrence of postoperative pain.[39] It is also observed that nonvital pulp teeth presented with more pain at 6 h and continued till 48 h irrespective of file system and motion used.[7]

Studies have reported that instrumentation using rotary instruments extruded significantly more debris than instrumentation with reciprocating files.[1416] Furthermore, the association of debris extrusion and increase of bacterial colonies in the conventional multi-file rotary system is greater when compared to the reciprocating single-file instrumentation.[37] On the other hand, studies demonstrated that full-sequence rotary instrumentation was associated with less debris extrusion when compared with the use of reciprocating single-file systems. Their explanation was that preenlargement of coronal third allows for the removal of debris.[132122] This inconsistency between studies might be attributed to the differences in the experimental setup and design.

This systematic review included studies that have used different rotary and reciprocating files. Reciprocating files used were WaveOne and Reciproc. Both systems are NiTi files treated with M-Wire technology and use a single instrument for cleaning and shaping of root canal system. The instruments are designed to work with a reverse cutting action. WaveOne system has three instruments that can be used according to the initial diameter of the main root canal. All instruments have a modified convex triangular cross-section at the tip end and a convex triangular cross-section at the coronal end. Reciproc file system is also composed of three instruments that have a noncutting tip and a S-shaped cross-section.

The rotary systems used were OneShape, ProTaper, Protaper Next, MTwo, and RaCe. OneShape is a one single NiTi instrument in continuous rotation with asymmetrical cross-section along the entire blade, variable cross-section and longer pitch. ProTaper is a NiTi system containing six regular files with triangular section, variable helical angle, noncutting guide tip, and multiple conicities. Differently, ProTaper Next is a unique asymmetric rotary motion for added efficiency, with an off-centered rectangular cross section for increase file strength. Mtwo system has several instruments that have an S-shaped cross-section and two efficient cutting edges It is designed with minimum radial contact as well as large deep flutes for continuous upward evacuation of dentinal chips. RaCe has a NiTi alloy with triangular section, alternate cutting edges, rounded safety tip and final treatment with electronic polishing.

Among the researches, different types of files were used and due to their peculiar characteristic distinct results were achieved. This can be the explanation for the heterogeneity of results. Although all the files are different, the main objective of this systematic review was to compare the two different motions (rotary and reciprocating) regarding the postoperative pain. Afterwards, reciprocating motion seems to have better results than rotary.

Both genders were analyzed in all the studies with exception of Relvas et al., 2016, that only analyzed the male gender because it is reported that women are more susceptible to postoperative pain.[40] Despite that, all studies using both genders did not report any difference between them regarding to the postoperative pain.[7]

NaOCl was the first choice of irrigating solution. Some studies have reported the toxicity and aggressiveness of the substance. Nevertheless, considering the use of the irrigant only into the root canal space without extravasation to the periapical region, and its capacity of eliminating organic substances, killing microorganisms, lubricating root canal, and helping on the elimination of dentinal chips it is proved to be safe for use.[41] Nekoofar et al., 2015, only used chlorhexidine and their explanation was to avoid any confounding effect of irrigating solution and/or intracanal medication.

Currently, it is known that the instruments do not reach each part of the complex root canal system during cleaning and shaping. With this knowledge in mind, the modern scientific community have encouraged the use of chelating substances such as EDTA and the final rinse with the aid of ultrasonic tips.[2342] Nevertheless, only three studies selected in our systematic review cited the use of ultrasound in their papers.[51023]

Krithikadatta et al., 2016 performed two visits endodontic treatment, using calcium hydroxide as an intracanal medication. Nekoofar et al., 2015 also prefer moded two visits treatment, although not using any dressing between appointments. All other studies reported single visit treatment. Single visit root canal treatment has been shown to produce lower levels of postoperative pain than multi visit treatments,[43] but the cited researches performed two visits to try to avoid confounding response related to the obturation process. All the sealers used and cited in the articles have excellent biocompatibility and great properties for tissue repair.[57922] Moreover, the obturation techniques are consolidated into the literature as being efficient.[57922]

Regarding to medication intake, some studies gave a single dose of analgesic after endodontic treatment in order to prevent acute and severe pain in the 1st h, as well as to avoid facial pain caused by lengthy appointments.[921] Also, most clinicians prescribed analgesic as needed.[57102223] They observed no statistically significant differences between instrument motions on analgesic intake.

In addition to postoperative pain Pasqualini et al., 2015 evaluated some indicators of postoperative quality of life such as difficulty eating, performing daily activities, sleeping, and social relations. Their results showed that the activities cited were more significantly affected by reciprocating instrumentation than rotary instrumentation. They concluded that reciprocating motion had an impact on immediate postoperative discomfort when preexisting periradicular inflammation was present and treatment was performed in a single visit, thereby negatively influencing patients' quality of life.

In addition to overall postoperative pain, the nature of pain (mild, moderate and severe) after 12, 24 and 48 h was analyzed as a secondary outcome. It is known that in the 1st h after endodontic treatment, there is a pain peak, which is uniquely related to the presence of inflammation. After day 1, pain begins to decrease significantly. In spite of this occurrence statistically difference in severe pain after 48 h was observed in this meta-analysis. Rotary instrumentation generated more events of pain confirming the hypothesis that rotary motion causes more postoperative pain after endodontic treatment.

To be qualified to participate on our meta-analysis, the research must have been evaluated by VAS, informed the number of patients with the presence or absence of pain and ranked the pain into mild, moderate and severe. For the sub analysis, it must have been presented the number of patients with pain after 12, 24, and 48 h and the same ranking.

Only five out of ten studies fulfilled the requirements to participate in this meta-analysis, showing the importance of continuous research in this matter from our scientific community in order to confirm the presented result.

CONCLUSION

This systematic review and meta-analysis indicates that rotary motion had a negative impact on postoperative pain after endodontic treatment. In addition, more patients presented with severe pain after 48 h under rotary motion compared to reciprocating motion. Additional randomized clinical studies are required on this subject.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.