Description

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.