Comparison of Postoperative Pain After Canal Instrumentation with Self-Adjustable File, Standard Technique and New Technique of ProtTaper Gold System: A Randomized Clinical Trial Study

Introduction: Postoperative pain is a common complication in endodontic procedures, influenced by various factors, including the instruments used for canal preparation and their kinematics. This study aims to compare the incidence of postoperative pain following the use of a new technique, the standard technique of the ProTaper system, and self-adjustable files in root canal preparation.
Methods: This randomized, controlled, parallel clinical trial aimed to evaluate post-endodontic pain associated with three distinct root canal cleaning and shaping techniques: the standard technique, a new technique using the ProTaper system, and the self-adjusting file system. A total of 123 mature permanent teeth requiring root canal treatment (RCT) from participants aged 10 to 65 years were selected through systematic randomization. All procedures were performed by a single operator in one center, utilizing loop magnification and isolation during a single visit for cleaning and shaping the canal. The samples were categorized into three groups: Group A (Standard technique using ProTaper gold rotary files), Group B (New sequence of ProTaper gold rotary files), and Group C (Self-adjusting files). The data collected from the participants were analyzed statistically using SPSS 25. The chi-square test was applied for comparison between groups, with the level of significance set at p < 0.05.
Results: The incidence of postoperative pain in the SAF group was notably lower compared to the pain levels observed with both the new technique and the standard technique of the ProTaper systems. However, there was no significant difference in pain levels between the standard and new technique methods for cleaning and shaping the canals. Additionally, patients treated with the SAF method experienced pain that was not severe enough to require painkillers, and no analgesics were utilized.
Conclusion: In summary, while all instrumentation techniques may lead to some degree of postoperative pain, the results of this study favor the SAF system. It can be concluded that the SAF technique, using continuous irrigation, resulted in significantly lower pain levels compared to both the standard and new technique methods.

Introduction

Postoperative pain following endodontic treatment is an undesired condition that causes discomfort for both the patient and the clinician [1]. The occurrence of postoperative pain after endodontic treatment is quite common, with reports indicating that it affects between 25% and 40% of patients, regardless of the condition of the pulp or periradicular status [1], [2]. Postoperative pain has a complex origin and is a significant factor contributing to the rejection of dental treatments. One of the primary issues linked to postoperative pain is the extrusion of debris [3].

Root canal preparation is a crucial step in endodontic therapy, as it is essential to eliminate vital and necrotic tissue, microorganisms, and dentinal debris from the root canal system for successful treatment [4]. However, during this process, instrumentation and irrigation solutions can lead to the expulsion of debris (comprising necrotic tissue, microorganisms, pulpal fragments, and dentin particles) into the periapical area. This can trigger postoperative inflammation and potentially result in treatment failure [5]. The process of cleaning and shaping the root canal system involves removing both organic and inorganic waste. Organic debris consists of pulpal tissues, microbes and their toxins, as well as any foreign materials that may have entered the root canal. In contrast, inorganic debris includes minerals and other substances that accumulate during the instrumentation process [6].

Additionally, various factors can contribute to postoperative pain, such as the use of different motion kinematics, the sizes of apical preparations, the number of treatment visits, obturation techniques, trauma to the periapical tissue, inflammation of the tissue, and pre-existing conditions prior to the procedure [1]. Although all instrumentation methods and tools can produce debris extrusion, the design of the files can impact the extent of this extrusion [7]. Most nickel-titanium (NiTi) instrument systems operate using a crown-down technique with push-pull rotational movements. Recent advancements in instrument design and varying operational principles can effectively reduce the amount of debris that is extruded [8].

ProTaper Universal (PTU; Dentsply Tulsa Dental, Tulsa, OK) is a well-established nickel-titanium rotary instrument system characterized by a gradual taper along the length of the cutting blades, a convex triangular cross-section, and non-cutting tips [9]. ProTaper Universal files are constructed from standard superelastic nickel-titanium wire. Previous research has indicated that the ProTaper Universal system was linked to a higher incidence of cracks compared to other nickel-titanium rotary instruments. The manufacturer of the ProTaper® Universal file system attempted to improve on the mechanical properties and performance of this popular system [10]. Recently, ProTaper Next was developed. ProTaper Next (Dentsply Maillefer, Ballaigues, Switzerland) is crafted from M-wire Nickel Titanium (Ni-Ti) alloy, enhancing its flexibility and resistance to cyclic fatigue. This system features both progressive and regressive percentage tapers, along with an off-centered rectangular cross-section, which contributes to its strength and effectiveness in shaping canals [8].

ProTaper Gold (PG) was created using advanced proprietary metallurgy and boasts a progressively tapered design that is said to enhance both cutting efficiency and safety. The geometries of PG rotary files are identical to those of ProTaper Universal (PU; Dentsply Maillefer, Ballaigues, Switzerland), although they may appear slightly curved when taken out of the packaging due to their unique metallurgy. This curvature is not considered a defect but rather an advantage according to the manufacturer. Additionally, the PG system has undergone metallurgical enhancement through heat treatment technology [11].

The SAF is notable for being the first file without a solid metal shaft [12]. Instead, it is designed as a hollow tube with walls made of a thin nickel-titanium lattice (Fig. 1), featuring a rough outer surface (Fig. 2). The tip of the file is asymmetrically positioned at the wall of the tube (Fig. 2), unlike traditional nickel-titanium rotary files that have symmetrically centered tips. The SAF system is highly flexible and compressible [13]. When used with continuous irrigation of any chosen solution, it operates in a vibrating motion [2].

Fig. 1. The self-adjusting file: (a) the file, (b) magnification of the lattice structure [13].

Fig. 2. The self-adjusting file: (a) The rough surface of the file, all components of the file have this rough surface, (b) the asymmetrical tip of the file, (c) flexibility of the file [13].

The purpose of this study was to clinically compare the incidence of postoperative pain after root canal instrumentation using three systems: a new technique, a standard technique, and self-adjustable files.

Materials and Methods

This randomized, controlled, parallel clinical trial was designed to compare post-endodontic pain associated with three different root canal cleaning and shaping techniques: the standard technique, the new technique, and the self-adjusting file system. This study was conducted in full compliance with the ethical principles outlined in the Declaration of Helsinki, ensuring the protection of the rights, dignity, and welfare of all participants. Ethical approval for the research was obtained from the Ethics Committee of Herat University (Approval Number: 14, Date: 11.1.2024). All participants provided written informed consent prior to their inclusion in the study.

In this study, a total of 123 mature permanent teeth requiring root canal treatment (RCT), whether with vital or non-vital pulp, were selected from participants aged 10 to 65 years. Patients were selected through systematic randomization at the Erfan Specialized Dental Clinic. The sample size was determined based on the number of patients who received endodontic treatment in the four months prior to the beginning of the trials. This helped estimate the number of patients who could be treated during the four-month trial period at the clinic. One specialist was responsible for the random allocation sequence, participant enrollment, consent taking, follow-ups, and record-keeping.

Trial Duration

The trials lasted four months, from March 2024 to June 2024. The study design followed a parallel model, with strict protocols for sampling, procedures, and record-keeping to minimize error. Participants were chosen using allocation concealment, with closed envelopes being used for this process.

Inclusion and Exclusion Criteria

The inclusion criteria consisted of patients of both genders, above the age of 10, otherwise healthy, and requiring endodontic treatment of permanent teeth with clinical signs of pulpitis or necrotic pulp, without any periapical pathology or infection. The treatment was to be done in a single session without complications or systemic problems.

Exclusion criteria included patients with systemic diseases, compromised immunity, or those requiring complicated endodontic treatment. Also excluded were patients with periapical pathology, retreatment needs, pregnant women, previously treated teeth, teeth with periodontal problems, patients who had taken analgesics 24 hours before treatment, and those with calcified or complicated canal configurations. Patients who did not comply with the criteria or failed to follow instructions after treatment were removed from the trial.

The criteria for endodontic treatment were established and recorded for each patient, along with the reason for treatment and clinical findings at the time of the procedure, in their files. All collected data from participants were analyzed using SPSS 25, and the chi-square test was applied for comparisons between groups.

Preoperative Evaluation

Before treatment, each tooth was examined clinically and with periapical digital radiography. The clinical evaluation included percussion, palpation, tooth mobility, pulp sensitivity tests (cold and electronic pulp tester), and cavity preparation tests.

Treatment Protocol

All treatments were performed by one operator at the Erfan Dental Clinic. Each treatment was carried out under loop magnification and isolation, with a single visit for cleaning and shaping of the canal. Sodium hypochlorite (NaOCl) at a concentration of 2.5% was used for irrigation of the root canal system. The samples were divided into three different groups: Group A (Standard technique with ProTaper Gold rotary files), Group B (New sequence of ProTaper Gold rotary files), and Group C (Self-adjusting files). The detailed treatment protocol for each group is described below:

• (Group A) Standard Protocol:

1. Preoperative periapical radiograph.

2. Use of ProTaper Gold system (Dentsply Sirona, Maillefer Instruments Holding Sàrl, Switzerland) files.

3. Follow the standard filing protocol according to the company’s instructions (Fig. 3).

4. Rinse with 0.2% Chlorhexidine solution for 20 seconds before administering the anesthetic injection (Protect Mouthwash with Fluoride 110 ml, Pakistan).

5. Local anesthesia using 2% Lidocaine with Epinephrine 1/100,000 (Medicine Inj, HSC Co. Ltd, Korea).

6. Isolation of the tooth.

7. Access cavity preparation using high-speed burs.

8. Primary working length determination with a #10 SS file and apex locator (DentalPort Root ZX II, Morita, Japan).

9. Use of shaping files from the ProTaper Gold system (Dentsply Sirona, Maillefer Instruments Holding Sàrl, Switzerland).

10. Final working length determination with apex locator (DentalPort Root ZX II, Morita, Japan).

11. Confirm working length with a periapical radiograph.

12. Use finishing files according to the canal gauge.

13. Use copious irrigation with NaOCl 2.5% during each filing step and employ a patency file.

14. Dry the canal with paper points and use a steel cotton plug and temporary filling for the next visit.

15. No intra-canal medication was used.

• (Group B) New Sequence, according to Machado et al. [15]:

1. Preoperative periapical radiograph.

2. Use of ProTaper Gold system (Dentsply Sirona, Maillefer Instruments Holding Sàrl, Switzerland) files.

3. Follow different filing protocols according to Machado et al. [15] (Fig. 4).

4. Rinse with 0.2% Chlorhexidine solution for 20 seconds before administering the anesthetic injection (Protect Mouthwash with Fluoride 110ml, Pakistan).

5. Local anesthesia using 2% Lidocaine with Epinephrine 1/100,000 (Medicine Inj, HSC Co. Ltd, Korea).

6. Isolation of the tooth.

7. Access cavity preparation using high-speed burs.

8. Primary working length determination with a #10 SS file and apex locator (DentalPort Root ZX II, Morita, Japan).

9. Use shaping files (Sx, S2, S1) from ProTaper Gold system (Dentsply Sirona, Maillefer Instruments Holding Sàrl, Switzerland) up to the provisional working length.

10. Final working length determination with apex locator (DentalPort Root ZX II, Morita, Japan).

11. Confirm working length with a periapical radiograph.

12. Use finishing files with a crown-down approach.

13. Use ProTaper S2 (until resistance) and S1 (until working length).

14. Use ProTaper F3 (until resistance), F2 (until resistance), and F1 (until working length).

15. Use ProTaper F3 (until resistance), F2 (until working length).

16. Use F3 until working length.

17. Use copious irrigation with NaOCl 2.5% during each filing step and employ a patency file.

18. Dry the canal with paper points and use a steel cotton plug and temporary filling for the next visit.

19. No intra-canal medication was used.

•(Group C) Self-Adjusting Files (SAF) System:

1. Preoperative periapical radiograph.

2. Use of Self-Adjusting Files (SAF system, ReDent NOVA, Israel) files.

3. Follow SAF protocol for filing according to company instructions (Fig. 5).

4. Rinse with 0.2% Chlorhexidine solution for 20 seconds before administering the anesthetic injection (Protect Mouthwash with Fluoride 110ml, Pakistan).

5. Local anesthesia using 2% Lidocaine with Epinephrine 1/100,000 (Medicine Inj, HSC Co. Ltd, Korea).

6. Isolation of the tooth.

7. Access cavity preparation using high-speed burs.

8. Primary working length determination with a #10 SS file (DentalPort Root ZX II, Morita, Japan).

9. Use pre-SAF OS file.

10. Use pre-SAF1 (#15/.02).

11. Use pre-SAF2 (#20/.04).

12. Final working length determination with apex locator (DentalPort Root ZX II, Morita, Japan).

13. Confirm working length with a periapical radiograph.

14. Use the SAF file with a 1.5 or 2 mm diameter with endostatin up to the working length.

15. Use copious irrigation with NaOCl 2.5% during each filing step with an Endostation irrigation system.

16. Dry the canal with paper points and use a steel cotton plug and temporary filling for the next visit.

17. No intra-canal medication was used.

•Post-Operative Follow-up:

1. After 24 hours, the patient was recalled to assess the presence or absence of pain. The patient's file was updated accordingly.

2. This study evaluated only the presence or absence of pain after endodontic treatment. The severity or degree of pain was not discussed.

3. All collected data were entered and analyzed using SPSS 0.25.

Fig. 3. Standard sequence of ProTaper file usage [14].

Fig. 4. New sequence of ProTaper files usage [15].

Fig. 5. Protocol for SAF usage according to manufacturer [13].

Result

A total of 123 patients were enrolled in this study. Two patients from the standard sequence group and one patient from the new sequence group were excluded because they could not be contacted for follow-up. The demographic data of the patients are summarized in Table I. The mean age of the participants was 32.7 years. According to the recorded data and the results of the chi-square test, there was a significant difference between the three methods of cleaning and shaping. The occurrence rate of postoperative pain in the SAF group was significantly lower when compared to the pain values in both the new sequence and standard sequence groups of the ProTaper Gold system (Table II). However, no significant difference was found between the standard and new sequence methods of cleaning and shaping the canals (Table III). Additionally, the highest amount of painkiller consumption after treatment was observed in patients whose canals were cleaned and shaped using the standard sequence method. This was followed by patients in the new sequence group, and finally, as shown in the data from Table IV, patients treated with the SAF method reported pain that was not severe enough to require painkillers, and no analgesics were used. Table V summarizes the baseline demographic and clinical properties of all study groups.

Table I. The Demographic Data of the Patients

Gender	Male	42	Age
	Female	81	10–20	15
Education	Illiterate	15	21–30	41
	Primary	10	31–40	47
	Elementary	13	41–50	11
	High school	33	51–65	9
	University	52	Total number of patients	123

Table II. Comparison of SAF, Standard Technique and New Technique of ProTaper

		Pain and discomfort		Total
		No	Yes
Techni ques of RCT	Standard technique	31	9	40
	New technique	37	4	41
	SAF	41	1	42
Total		109	14	123
Pearson Chi-Square		p = 0.01

Table III. Comparison of Standard Technique and New Technique of ProTaper System

		Pain and discomfort		Total
		No	Yes
Techniques of RCT	Standard technique	31	9	40
	New technique	37	4	41
Total		68	13	81
Pearson Chi-Square		p = 0.11

Table IV. Use of Analgesic Drug

		Use of analgesic drug		Total
		No	yes
Techniques of RCT	Standard technique	34	6	40
	New technique	39	2	41
	SAF	42	0	42
Total		115	8	123

Table V. Baseline Demographic and Clinical Features of the Patients in the Study Groups

Demographic and clinical features	Standard technique	New technique	SAF	Total
Male	15	16	11	42
Female	25	25	31	81
Vital	32	30	23	85
Non vital	8	11	19	38
Incisors	9	15	21	40
Premolars	19	17	10	41
Molars	17	9	11	42
Frequency of postoperative pain	9	4	1	14

Discussion

Research on postoperative pain in endodontics is crucial, as it provides valuable insights into managing and preventing pain following endodontic procedures. Such studies help clinicians develop effective strategies to minimize postoperative discomfort. By examining the factors that contribute to pain after treatment, clinicians can create treatment plans that alleviate patient suffering and improve overall outcomes.

In this study, a two-visit root canal treatment procedure was chosen. According to various studies, postoperative pain is significantly lower in single-visit treatments compared to multiple-visit treatments [16], [17]. This could be due to the treatment being less time-consuming and more cost-effective, while avoiding complications associated with intra-canal medications, excessive instrumentation, and irrigation, all of which may irritate the periradicular area and cause inter-appointment or postoperative pain [18]–[20]. However, a two-visit treatment plan was selected in this study because it allowed for examining pain immediately after root canal cleaning and shaping with the various systems, without the influence of pain related to canal obturation. Additionally, some studies report no significant difference in the frequency of pain after single- or multiple-visit treatments [21].

Although multiple factors contribute to postoperative pain, one of the main causes is the potential extrusion of debris and irrigants beyond the apex into the periapical region (2). Standard root canal preparation has been performed using various instruments and kinematic techniques. Recent technological advancements in endodontic instrumentation have introduced innovative designs that promise more efficient and quicker preparations while preserving the original shape of the canal and reducing debris extrusion and other iatrogenic errors. Manufacturers assert that these new systems result in improved treatment outcomes and a lower incidence of postoperative pain [22].

The techniques used for root canal preparation vary in the quantity of extruded debris, with some methods resulting in less extruded material than others. In this study, the reduced pain levels in the SAF group may be attributed to the lower amount of bacteria, irrigants, dentin debris, and inflamed pulp tissue being extruded apically, which can contribute to postoperative discomfort. The SAF system is a single-file instrument that lacks a central metal core, cutting edges, or flutes. Instead, it features an abrasive surface and is used with continuous irrigation. This constant flow of irrigant prevents the buildup of pressure within the root canal, as the metal mesh structure allows the irrigant to escape unobstructed. Some studies report that SAF extrudes less debris [6]. The SAF system's metal structure adapts to the contours of the canal walls and effectively removes dentin through a back-and-forth motion. This action provides a cleaning effect on the root canal walls, while the vibrating motion helps agitate the irrigant within the canal, promoting continuous irrigation. The solution can flow out through the perforations in the file's lattice [12].

In a study comparing the extrusion of debris, although there was no statistically significant difference between SAF and ProTaper systems, the ProTaper group had the highest mean extrusion value [5]. ProTaper files generate a mechanical wave along their active length, which reduces the contact between the file and dentin, potentially aiding in debris evacuation from the canal and enhancing the flexibility of the files [23]. Another study indicated that the ProTaper system expelled more debris from the apex compared to the SAF system [4]. This difference in debris extrusion may be attributed to the distinct designs and movements of the files in each system. The SAF system facilitates continuous irrigation during root canal cleaning and shaping, helping to push debris coronally out of the canal and minimizing the amount of material pushed apically.

Different instrumentation systems are linked to varying levels of postoperative pain [24], [25]. Based on the current study, the level of pain after root canal treatment in the group where canal preparation and shaping were performed using self-adjusting files (SAF) was significantly lower than in the other two methods. However, no significant difference was found between the standard and new sequence methods. In this study, patients were advised to take Ibuprofen if they experienced pain after treatment. Ibuprofen is the preferred nonsteroidal anti-inflammatory drug for managing postoperative pain following root canal treatments. Notably, none of the patients in the SAF group reported taking analgesics, indicating a low intensity of pain. In contrast, analgesic use was reported after treatment in the other two groups.

One study comparing postoperative pain in different file systems found that the SAF group had lower pain intensity and minimal analgesic intake compared to the ProTaper group. The potential reasons for this could include: 1) the continuous flow of fresh, activated irrigants, 2) the lack of positive pressure, which allows the irrigant to escape easily through gaps in the file's lattice, and 3) the anatomical shaping of the root canals in the SAF group, such as a smaller core size that creates space for debris to migrate coronally [26]. Therefore, we can conclude that the innovative self-adjustable file technique effectively reduces the risk of pushing debris apically, which can lead to increased postoperative pain.

Conclusion

In conclusion, all instrumentation techniques may lead to some level of postoperative pain. The results indicated that while each technique caused minor pain, it was generally mild and did not require further treatment. It can be concluded that the SAF technique, which utilizes vibratory motion with continuous irrigation, resulted in significantly less pain compared to both the standard and new sequence methods. The findings of this study support the SAF system, but further clinical research on post-instrumentation pain associated with these systems is needed to enhance our understanding of the SAF technique and its potential benefits.