Title

Evaluation of the Effect of Reciprocal and Rotational NiTi File Systems and XP-Endo Finisher Combination on Postoperative Pain

Clinical Research Protocol Summary Objective

The aim of this study is to compare the effects of different NiTi file systems (FKG Race Evo and One Reci) and their combination with XP-Endo Finisher on postoperative pain. The study intends to evaluate how these two different file systems and XP-Endo Finisher influence patients' pain levels after endodontic treatment. It is also hypothesized that XP-Endo Finisher may play an important role in reducing postoperative pain by enhancing irrigation efficacy. This study is expected to contribute clinically significant findings to the limited literature on this topic.

Background

Endodontic treatment is a procedure performed to mechanically shape, disinfect, and hermetically seal teeth with pulpal damage or periapical lesions caused by caries or trauma. The success of treatment depends on proper shaping within biological limits, effective disinfection, preservation of apical constriction, and removal of bacteria from canal walls.

NiTi alloys have improved canal shaping efficiency due to their flexibility and shape memory properties. Rotary and reciprocating NiTi systems each offer different clinical advantages. Rotary systems provide efficient shaping through continuous rotation, while reciprocating systems offer a minimally invasive approach using a single file.

Postoperative pain is a common complication after endodontic treatment and may vary depending on instrumentation technique, irrigation protocol, and clinical conditions.

Irrigation is essential for removing microorganisms and debris from the canal system. Conventional irrigation techniques may be insufficient to reach apical areas effectively. Therefore, advanced systems such as XP-Endo Finisher have been developed to improve irrigant penetration and enhance cleaning efficiency.

FKG Race Evo is a rotary NiTi system with high cyclic fatigue resistance, while One Reci is a reciprocating single-file system that offers safe shaping with reduced procedural errors. This study will evaluate the postoperative pain outcomes of these systems in combination with XP-Endo Finisher.

Materials and Methods

The materials used in this study include FKG Race Evo and One Reci NiTi file systems, XP-Endo Finisher, 2.5% sodium hypochlorite (NaOCl), 17% EDTA, and saline solution.

The study will be conducted on 80 patients attending the Department of Endodontics, Faculty of Dentistry, Eskisehir Osmangazi University. Healthy individuals aged 18-65 years with chronic apical periodontitis or periapical radiolucent lesions will be included. Written informed consent will be obtained from all participants.

Patients will be randomly divided into four groups:

Group 1: Instrumentation with FKG Race Evo 25/06 Group 2: FKG Race Evo 25/06 followed by XP-Endo Finisher irrigation Group 3: Instrumentation with One Reci 25/06 Group 4: One Reci 25/06 followed by XP-Endo Finisher irrigation

All procedures will be performed under rubber dam isolation and local anesthesia. Canal shaping will be performed according to the assigned system, with irrigation performed after each file change. Obturation will be completed in the second session.

Sample Size Calculation

The sample size was calculated using G*Power software (3.1.9.4; Heinrich Heine University, Düsseldorf, Germany). The calculation was based on a 5% type I error (alpha), 95% power (1-β), and an effect size of 0.587 (f), derived from a previous study. A total of 80 participants was determined to be sufficient to detect statistically significant differences between groups. Each group will include 20 patients.

Statistical Analysis

All data will be recorded electronically with strict confidentiality. Only authorized researchers will have access to the dataset.

Statistical analysis will be performed using appropriate software. The choice of statistical tests will depend on data distribution.

Study results may be published in national or international peer-reviewed journals in accordance with ethical and legal requirements. All data will be anonymized to protect participant confidentiality, and secure electronic storage will be used to prevent unauthorized access.

The aim of root canal treatment is to prevent infection in teeth with pulp exposed to the oral environment due to caries or trauma, or in teeth with periapical lesions, by applying mechanical shaping, irrigation, and disinfection. Successful endodontic treatment depends on shaping the root canal system within biological limits, effective disinfection, hermetic obturation, and completion of restoration with an appropriate coronal restoration. For this purpose, mechanical preparation and irrigation solutions are used together.

The criteria under the operator's control in root canal treatment include factors that determine treatment success. These include infection control, proper application of canal shaping techniques, and effective distribution of intracanal medicaments and cleaning solutions. In particular, the mechanical shaping stage plays a critical role in removing microorganisms and tissue debris within the canal system. The removal of infected pulp tissue, bacteria, and necrotic debris without causing damage to the periradicular area is an important part of treatment. In this way, the spread of infection is prevented and treatment success is increased. Maintaining apical constriction during preparation and preventing extrusion of debris, bacteria, and irrigants from the apical region is very important. Extruded materials may cause increased inflammation, postoperative pain, and delayed periapical healing. Therefore, controlling irritants originating from the apical region and preventing extrusion increases treatment success.

Root canal preparation instruments have undergone significant changes over time and have made important progress with technological developments in the last 25-30 years. During root canal preparation, various instruments are used. These include stainless steel hand files (K-type files, Hedström files, reamers), low-speed instruments (Peeso, Gates Glidden), motor-driven NiTi rotary files, reciprocating NiTi endodontic motors and files, and ultrasonic instruments. These instruments provide different advantages in shaping and cleaning the root canal.

Traditionally, root canal shaping is performed using stainless steel hand instruments manufactured according to ISO (International Organization for Standardization) standards with a 0.02 taper. The variability among stainless steel hand files is achieved through differences in cutting blade angle, depth, cross-sectional design, and tip modifications. Stainless steel hand files generally have 16 mm of cutting blades, and for each 1 mm, the diameter increases by 0.02 mm. In addition, tip designs differ in terms of cutting efficiency. K-type files are used with quarter-turn and pull motion, while Hedström files are used only with pull motion. The disadvantages of stainless steel hand instruments include lack of elasticity. Therefore, they may cause operator-related errors, especially in curved canals. In addition, low taper angles may make it difficult to properly shape the canal from apical to coronal direction. This may lead to apical extrusion of debris during canal shaping and reduced effectiveness of irrigating agents.

Since the beginning of the 20th century, various motor-driven systems have been developed after hand instruments to facilitate shaping and cleaning procedures. In the early 1960s in the United States, metallurgist Buehler investigated non-magnetic and waterproof alloys and developed NiTi alloys. NiTi alloys differ from other alloys with four properties:

Low elastic modulus (35 KN/mm²) Very high flexibility (4-8%) Shape memory effect Pseudoelasticity (superelasticity)

NiTi rotary files demonstrate better performance compared to stainless steel hand instruments in terms of penetration into canals. In addition, they provide advantages in mechanical properties and interaction with irrigating solutions. According to studies, the advantages of NiTi files include ease of use for the clinician, effective debris removal, creation of ideal taper, better preservation of tooth structure, reduced canal transportation, and shorter preparation time compared to hand files. The introduction of NiTi rotary instruments has made root canal preparation more predictable in clinical settings, shortened procedure time, and reduced clinician stress. The rotational motion developed in the late 1980s is still widely used in many mechanical preparation systems today. This motion involves continuous 360° rotation of NiTi files within the root canal. Compared to traditional hand files, rotary systems provide more effective shaping and cleaning of root canals. These systems allow more homogeneous and tapered canal shaping, while also enabling irrigants to reach deeper areas, thereby increasing treatment success.

To reduce the risk of instrument fracture, new motion strategies have been proposed. Yared's 2008 study demonstrated that a single ProTaper F2 file used with reciprocating motion moves alternately clockwise and counterclockwise with different angles while advancing apically, applying minimal apical stress, and showing that full canal preparation can be performed with a single file.

With the introduction of single-file systems and reciprocating motion in endodontics, several advantages have been achieved such as shorter procedure time, increased patient comfort, reduced cross-contamination risk, reduced file fracture, and cost-effectiveness. In these systems, the counterclockwise and clockwise movements are asymmetric, and the larger reverse angle works similarly to a balanced force technique, providing effective shaping.

One Reci (Micro-Mega, France), developed in 2016, is a single-file system used in routine dental treatments and operates with reciprocating motion. The OR system is heat-treated (C-wire) to increase flexibility and improve centering within the canal. It has a variable cross-sectional design starting with a triple helix and transitioning into an S-shape toward the body, allowing efficient removal of debris from the coronal region. This feature provides high cutting efficiency. The system operates with 170° counterclockwise and 60° clockwise rotation. The file sizes are 20.04, 25.04, 25.06, 35.04, and 45.04. Due to this design, the One Reci system contributes to preservation of original canal anatomy by minimizing dentin removal, especially in narrow and curved canals. Comparative studies have reported that One Reci shows similar or superior performance to systems such as ProTaper Next and Reciproc Blue in reducing canal transportation and shortening shaping time.

The Race EVO system (FKG Dentaire SA, Switzerland), used with rotational motion, is a single-file system first introduced in 2010 and used in routine dental treatments. It is a new-generation rotary system characterized by optimized cutting efficiency, low torsional stress, and high cyclic fatigue resistance. Its triangular cross-section and alternating cutting edges reduce the screwing effect and allow safe progression within the canal. The files are available in 4% and 6% taper and are used at 800-1000 rpm with 1.5 Ncm torque. The rounded safety tip and electropolished surface reduce fracture risk and improve surface smoothness. Therefore, Race EVO is described in the literature as a fast, safe, and efficient rotary NiTi system. Comparative studies have shown that Race EVO significantly reduces canal transportation and unnecessary dentin removal compared to systems such as ProTaper Gold and Reciproc Blue.

After root canal treatment, patients often experience postoperative pain of varying intensity within the first few hours or days. This pain occurs in approximately 3% to 58% of patients, creating an important concern for both patients and clinicians. In Pak and White's 2011 study, postoperative pain was reported in approximately 40% of cases within 24 hours, decreasing to around 11% within 7 days. Possible sources of postoperative pain include chemical, mechanical, or microbiological injury to periapical tissues. Such irritation may lead to periapical inflammation and acute exacerbations in approximately 1.4-1.6% of cases. In teeth with necrotic pulp and asymptomatic periapical lesions, acute exacerbation may occur within 24-48 hours after initial treatment. Postoperative pain is generally highest within 2-7 days after treatment and is significantly higher compared to 8-30 days.

Compared to manual files, rotary NiTi systems have been reported to reduce postoperative pain by 68% in patients undergoing root canal treatment. However, there is no consensus in the literature regarding postoperative pain differences between rotary and reciprocating systems. Some studies report lower postoperative pain in rotary systems. This has been attributed to less apical extrusion of debris. Other studies report lower pain in reciprocating systems, suggesting that rotary systems may cause more canal straightening compared to reciprocating motion.

Irrigation is a fundamental step in endodontics that supports mechanical preparation and removes microorganisms, smear layer, and organic/inorganic debris from the root canal system. Although conventional needle irrigation is widely used, it has limitations in reaching the apical region. Therefore, ultrasonic, sonic, laser-assisted, and negative pressure irrigation techniques have been developed to improve irrigant activation and disinfection. In this context, XP-Endo Finisher is a modern instrument that contributes to removal of debris, smear layer, and microorganisms from difficult-to-reach areas of the root canal system. Due to its thermomechanical properties, it undergoes phase transformation at body temperature and expands to adapt to canal anatomy, allowing better contact with dentinal walls. This adaptive behavior facilitates more homogeneous distribution of irrigants and increases irrigation efficiency compared to conventional methods. With all these properties, XP-Endo Finisher is considered an innovative adjunct tool that enhances irrigation effectiveness in endodontic treatment.

Inclusion Criteria:

• Age 18-65 years. Healthy volunteers. Mandibular molar teeth with pulpal necrosis, asymptomatic status, chronic apical periodontitis, and periapical radiolucent lesion.

Written informed consent.

Exclusion Criteria:

• Patients who have taken analgesic or anti-inflammatory drugs within the last 12 hours.

Patients with allergy to non-steroidal anti-inflammatory drugs or local anesthetics.

Pregnant or lactating patients. Patients with a history of gastrointestinal diseases. Patients using opioid medications. Teeth with calcified canals, resorptive defects, or complex root canal anatomy. Patients with severe periodontal disease. Patients with acute or chronic apical abscess or signs of systemic infection. Immunosuppressed patients.