The effect of various kinematics on postoperative pain after instrumentation: a prospective, randomized clinical study

ABSTRACT Objective: To evaluate various kinematic movements on postoperative pain using a Reciproc system. Material and Methods: Fifty-six molar teeth were divided into four groups according to kinematics as follows: continuous rotation, 360° CCW – 30° CW, 270° CCW – 30° CW, and 150° CCW – 30° CW. Preoperative and postoperative pain levels using visual analogue scale (VAS), percussion pain, and analgesic intake were recorded for each subject. Postoperative pain levels at 1, 3, 5, and 7 d were evaluated. Data were analyzed statistically using the Kruskal-Walis, Mann-Whitney-U, one-way analysis of variance, and chi-square tests (p=0.05). Results: Continuous rotation resulted in more pain at Day 1 when compared with the reciprocating groups (360° CCW – 30° CW and 270° CCW – 30° C) (p<0.05). Conclusions: Continuous rotation resulted in more postoperative pain at Day 1 than in reciprocating groups, and thereafter no significant pain was found among the groups.


INTRODUCTION
One of the most important matters in endodontic treatment is the prevention of pain. Postoperative pain after endodontic treatment is a frequent complication. According to a systematic review, the frequency of endodontic postoperative pain in patients is between 3% and 58% 11 . Postoperative pain can be affected by almost all of the procedures in root canal treatment, including anaesthesia administration 6 , introduction of glide path 8 , use of instrumentation systems 4,5 , and retreatment 13 .
Reciproc system (VDW, Munich, Germany) is characterized by an S-shaped cross section. It has sharp cutting edges and a non-cutting tip. It shapes the canals with a reciprocal back-and-forward motion (150 degrees counterclockwise and then 30 R50 (50/0.05) 2 . These instruments are produced with a special NiTi alloy (M wire) subjected to a special thermal treatment process, performed to 9 .
Previous studies have reported conflicting results on postoperative pain regarding the effect of instrumentation using reciprocating and rotation 4,5 . Neelakantan and Sharma 4 (2015) evaluated postoperative pain after instrumentation of root canals with a single-file reciprocating (Reciproc) and rotary (One Shape, MicroMega, of postoperative pain than One Shape. However, Nekoofar, et al. 5  designs and/or the number of instruments used. We believe that there is nothing about the effect of different kinematics using the same instruments on postoperative pain in the literature. Therefore, the purpose of this study was to evaluate four (combinations of) kinematic movements [counter clockwise (CCW) continuous rotation, 360° CCW -30° clockwise (CW), 270° CCW -30° CW, and 150° CCW -30° CW] regarding postoperative pain using just one type of instrument, a Reciproc system. The null hypothesis was that there is no difference among the groups in postoperative pain. 4-Patients with a preoperative pain level from 0 to 25 on the visual analogue scale (VAS) of 100 mm length.

Exclusion criteria
1-Palpation pain; 2-Bruxism or clenching; 3-Antibiotics or analgesics taken in the past 24 h; 4-Previous root canal treatment; 5-Swelling or sinus tract; 6-Severe periodontal disease; 7-Pocket depth greater than 5 mm; 8-Mobility greater than grade 1; 9-Periapical radiolucency; 10-Severely damaged teeth; 11-Absence of occlusal contact; 13-Teeth with problems, such as overdetermining working length. The patients were randomly distributed into the groups using a web program (available at www. randomizer.org). Patient and group numbers were recorded on paper. After each patient signed the informed consent form, the tooth was anesthetized with a local anaesthetic solution containing 1.7 mL of 4% articaine with 1:100 000 epinephrine (UltracaineDS ® forte; Aventis, Istanbul, Turkey). A were performed. The procedure was initiated 15 min later.
After a straight-line access cavity was prepared, the procedure was completed under rubber-dam isolation. The working length was determined by an electronic apex locator (Root ZX mini; J. Morita Mfg Corp., Kyoto, Japan), and the Reciproc instruments were used according to the manufacturer's instructions. A new Reciproc instrument was used for each patient. Palatine canals of maxillary molars The patients were divided into four groups (n=14) according to the kinematic movements, as follows: counterclockwise continuous rotation, 360° CCW -30° CW, 270° CCW -30° CW, and 150° CCW -30° CW.
For all groups, the speed of the motor was adjusted to 300 rpm. For the continuous rotation was used to maintain apical patency. For the irrigation, 2 mL of 1.25% NaOCl was used between in-and-out pecking motions with safety tip needle (Canal Clean; Biodent, Paju, Korea) approximately was performed using 1.25% NaOCl and 17% EDTA for 1 min to remove the smear layer.
After root canal preparation, the root canals matched single cones and AH Plus sealer (Dentsply De Trey GmbH, Konstanz, Germany). The pulp and a nanohybrid composite resin was inserted into the cavity using an incremental technique and cured for 20 s using a LED light-curing unit (Valo Cordless, Ultradent, South Jordan, UT, USA) with an output of 1000 mW/cm 2 . The patients were instructed to use 400 mg the pain was bearable and informed to record the analgesic intake on a customized form, which was also used by them to record any pain experience.
The following variables were recorded: Age; Gender; Tooth number; Preoperative pain on the VAS; Preoperative and postoperative percussion pain levels on the VAS; Pain level on the 1 st , 3 rd , 5 th , and 7 th days; Analgesic intake after the procedure. Change in pain was calculated at the related day based on the preoperative pain.

Statistical analysis
The Kolmogorov-Smirnov test for distribution of data for reduction in pain levels, according to the day, revealed non-normal distribution. Thus, data were analyzed using the Kruskal-Walis and Mann-Whitney-U tests for inter group analysis (p=0.05). The differences in age and preoperative and postoperative percussion pain levels were statistically analyzed using one-way ANOVA test (p=0.05). The differences in gender and analgesic intake were statistically analyzed using a chi-square test (p=0.05). Table 1 shows the demographic data related to age, gender, preoperative and postoperative percussion, palpation, swelling, and sinus tract. Figure 2 shows the reduction in pain levels at different time intervals. The Kruskal-Walis test at Day 1 (p<0.05), but not at the other time periods (p>0.05). Mann-Whitney U test revealed that continuous rotation resulted in more pain at Day 1 than in reciprocating groups (360° CCW -30° CW and 270° CCW -30° C) (p<0.05). The preoperative and postoperative percussion pain levels among the groups seven days after treatment were not statistically different (p>0.05).

RESULTS
None of the patients were referred to the clinic with swelling or sinus track after the treatment. Also, none of the patients needed an unscheduled appointment. Three patients in the continuous rotation group, two patients in the 360° CCW -30° CW group, one patient in the 270° CCW -30° CW, and two patients in the 150° CCW -30° CW group

DISCUSSION
Recently, Neelakantan and Sharma 4 (2015) and Nekoofar, et al. 5 (2015) evaluated postoperative pain after instrumentation of root canals with a However, one may argue that the different crosssections, speed, kinematics, and systems may have had an impact on the postoperative pain. It is necessary, therefore, to evaluate the effect of pure reciprocating or continuous rotary motions using instruments with the same cross-sections on postoperative pain. Thus, the purpose of this study was to evaluate various kinematic movements on postoperative pain using just one type of instrument, a Reciproc system. differences were found among the groups at Day 1 (p<0.05), but not at the other time periods (p>0.05) Thus, the null hypothesis was partially rejected.
An interesting finding was that continuous rotation resulted in more pain at Day 1 than in the reciprocating groups. Because there is no similar study in the literature, this finding cannot be compared with those of previous studies. Nekoofar, et al. 5 2015), the 150° CCW -30° CW and 270° CCW -30° CW reciprocating motions extruded (p<0.05). In this study, the continuous rotation resulted in more pain at Day 1 than in reciprocating groups (360° CCW -30° CW and 270° CCW -30° C). Although the 150° CCW -30° CW reciprocating continuous rotation in the laboratory study, in this the 150° CCW -30° CW reciprocating motions and continuous rotation. There are several explanations for the differences in the results of the studies, the most likely being the different methodologies (in vivo and in vitro) employed.