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BMC Oral Health
BMC Oral Health
BMC Oral Health
1472-6831
BioMed Central London

39261778
4833
10.1186/s12903-024-04833-2
Research
Evaluation of apically extruded debris during root canal filling material removal in teeth with external apical root resorption: a comparison of different obturation techniques
http://orcid.org/0000-0003-4092-7241
Çağlar Büşra Melike 1
http://orcid.org/0000-0003-3353-3260
Uzun İsmail ismail.uzun@omu.edu.tr

2
1 Endodontist, Samsun Central Dental Hospital, Samsun, Türkiye Turkey
2 https://ror.org/028k5qw24 grid.411049.9 0000 0004 0574 2310 Faculty of Dentistry, Department of Endodontics, Ondokuz Mayıs University, Samsun, Turkey
11 9 2024
11 9 2024
2024
24 106726 5 2024
29 8 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Background

Root canal retreatment is necessary when initial treatment fails. Nickel-titanium systems help remove filling materials; however, some methods can cause canal content extrusion, resulting in inflammation and delayed healing. This study aimed to examine the impact of different preparation techniques and endodontic file systems on apical debris volume to limit material dispersion to periradicular tissues.

Methods

Ninety extracted maxillary incisors were evaluated. Simulated apical root resorption was created by removing the apical 2 mm of the root. The teeth were divided into two groups: one filled with a single cone and the other with cold lateral compaction (CLC). Each group was further divided into three subgroups (n = 15 each): Subgroup 1 used Reciproc R25 for removal and R50 for final preparation; Subgroup 2 used ProTaper Universal Retreatment (PTUR) files D1, D2, and D3 for removal and ProTaper Next X5 for finalization; and Subgroup 3 used VDW.Rotate Retreatment (VDW.RotateR) for removal and VDW.Rotate 50.04 for completion. Debris from retreatment was collected in pre-weighed tubes to determine the amount. The apical extrusion data underwent a two-way analysis of variance.

Results

The Reciproc group had a mean extruded debris weight of 0.54 ± 0.24 mg, higher than the PTUR (0.28 ± 0.15 mg) and VDW.RotateR (0.39 ± 0.29 mg) groups (p < 0.05). The single-cone technique (SCT) resulted in a mean debris weight of 0.34 ± 0.23 mg, lower than the CLC technique, which had a mean of 0.46 ± 0.27 mg (p < 0.05). SCT had a shorter retreatment duration (111.12 ± 33.46 s) compared to CLC (176.26 ± 52.26 s) (p < 0.05).

Conclusion

The Reciproc file system and the CLC obturation technique resulted in greater apical debris extrusion than the other methods. SCT was quicker than CLC. The Reciproc groups are more susceptible to apex extrusion during retreatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-024-04833-2.

Keywords

Apical debris extrusion
Simulated apical root resorption
Endodontic
Retreatment
Reciproc
PTUR
VDW.rotateR
Ondokuz Mayis University Research FundPYO.DIS.1904.20.007 issue-copyright-statement© BioMed Central Ltd., part of Springer Nature 2024
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pmcBackground

Endodontic treatment is a cornerstone of dental practice, aiming to eliminate bacterial components and toxins by mechanically shaping the root canal system and filling it with materials to establish a three-dimensional seal from the coronal to the apical aspects. This comprehensive seal is essential to prevent reinfection and ensure the long-term success of the treatment [1]. However, despite significant advancements in endodontic techniques, achieving an effective seal remains particularly challenging in certain clinical scenarios. One such scenario is the absence of apical constriction, which can occur due to incomplete root development or external apical root resorption (EARR) [2]. EARR, which often goes unnoticed in radiographs, results from conditions such as periradicular inflammation, orthodontic treatment, or trauma. These conditions compromise the cementum layer, allowing infections in the dentinal tubules or bacterial mediators to induce inflammation in the periodontal ligament, potentially leading to root resorption [3]. Studies have shown that a significant proportion of teeth with apical periodontitis exhibit some level of root resorption, complicating the treatment process [4]. Hence, understanding the mechanisms and impact of EARR is crucial for developing effective treatment strategies in endodontics [5].

When initial root canal treatment (RCT) fails, retreatment becomes necessary. This is particularly common in cases involving complex root canal anatomy or EARR [4]. Effective removal of root canal filling material is crucial to achieving successful retreatment outcomes. Several tools and techniques, including nickel-titanium (NiTi) instruments, ultrasonic systems, laser systems, and chemical solvents, have been developed for this purpose [6]. Among the NiTi systems, the ProTaper Universal Retreatment (PTUR), VDW.Rotate Retreatment (VDW.RotateR), and Reciproc single-file systems are the most notable for their effectiveness in gutta-percha removal [7].

However, during the root canal preparation and removal of the root canal filling material, elements such as dentine chips, pulp tissue, microorganisms, or irrigants can be extruded into the periradicular tissues [8]. This extrusion can lead to adverse consequences, including inflammation, postoperative pain, flare-ups, and delayed periapical healing [9]. Research has indicated that all methods used for root canal preparation might cause the extrusion of varying amounts of canal contents beyond the apical foramen [10], with the design and kinematics of the endodontic files playing a role in this extrusion [11]. Therefore, evaluating the effectiveness of different NiTi systems in minimizing apically extruded debris, especially in teeth with EARR, is critical for improving retreatment success and patient outcomes [12, 13].

The primary objective of this study was to evaluate the quantity of apically extruded debris during the retreatment of teeth with simulated apical root resorption using different NiTi systems. In addition, it aimed to determine the time required for the removal of gutta-percha and sealer. These are pivotal to understanding the efficacy and relative cleanliness of the tested techniques. This research addresses a significant gap in the literature by comparing the performance of various NiTi systems in challenging clinical scenarios involving EARR. We hypothesized that there would be no significant differences in the amount of apically extruded debris among the various NiTi systems and obturation techniques. We believe that the findings of this study will provide valuable insights to clinicians in selecting appropriate retreatment strategies to minimize apical extrusion and improve patient outcomes [13, 14].

Materials and methods

This study was supported by the Samsun Ondokuz Mayis University Research Fund (PYO.DIS.1904.20.007). The research protocol was approved by the Clinical Research Ethics Committee of Ondokuz Mayıs University (2020/341). The study strictly adhered to the ethical guidelines outlined in the Declaration of Helsinki. Prior to initiating the study, the participants were informed about its purpose, procedures, and potential risks, and written informed consent was obtained from all of them.

Following the approval, 90 straight, single-rooted human maxillary incisor teeth (central and lateral), extracted due to periodontal reasons, were selected and evaluated. Each specimen’s external resorption, calcifications, cracks, fractures, caries, or previous RCT was examined using an x2.5 loupe (Eyemag Pro S, Zeiss, Oberkochen, Germany). Teeth exhibiting these features were excluded. Only teeth with a single canal in each root and a curvature less than 50 were included, as determined by Schneider’s method [15]. Before experimentation, teeth were stored in distilled water.

To simulate apical root resorption, the apical 2 mm of the root was removed using a fissure bur [16]. Endodontic access cavities were prepared using a high-speed carbide bur (Dentsply Sirona, Ballaigues, Switzerland) with cooling water. Canals with a diameter larger than ISO size 25 were excluded. All crowns were trimmed using a high-speed bur with water cooling to achieve a consistent 13-mm tooth length. The working length (WL) was defined by reducing 1 mm from the actual root length, determined by introducing a #10 K-file (Dentsply Maillefer) until visible at the apical foramen (Figs. 1 and 2).

Fig. 1 Teeth samples used in the study for evaluating apically extruded debris during root canal filling material removal

Fig. 2 Example of a tooth sample with 2 mm of the apical portion removed to simulate external apical root resorption

Chemomechanical preparation of the root canals was executed using the ProTaper Next (PTN) system (Dentsply Maillefer, Ballaigues, Switzerland) with an X4 file at the established WL, following the manufacturer’s guidelines. During preparation, the root canals were irrigated with 2 mL of 2.5% sodium hypochlorite (NaOCl) after using each file. Final irrigation consisted of 5 mL each of 17% ethylenediamine tetra acetic acid (EDTA), 2.5% NaOCl, and distilled water.

The prepared samples were then randomly divided into two equal groups: one utilized a single-cone filling method, while the other employed the cold lateral compaction (CLC) technique. Although the exact width of the apical resorption area was not measured in this study, the single-cone technique (SCT) was chosen based on clinical judgment and its frequent use in similar scenarios. If the resorption had been more extensive, other techniques would have been necessary. This technique allows for the evaluation of its effectiveness in cases where resorption is manageable with a single cone. AH Plus (Dentsply Sirona) was used as the sealer in both techniques due to its favorable sealing properties and widespread use in endodontics. AH Plus is an epoxy resin-based sealer known for its excellent flowability, adhesion, and biocompatibility, which can significantly influence the amount of extruded debris and the overall retreatment time [17]. Post-filling, specimens were stored at 37 °C in 100% humidity for 2 weeks to ensure a complete sealer setting. In addition, during canal preparation, a tug-back sensation was felt with the master gutta-percha cone, providing an estimate of the apical width and confirming the suitability of the SCT for the given cases.

For the collection of apically extruded debris, an opening was made in an Eppendorf tube lid to accommodate a tooth up to its cement enamel junction. A 27-gauge needle was positioned alongside the tube’s stopper to equilibrate internal and external pressures. Each tube, fitted with a tooth and needle, was then secured within a plastic cap, obscuring the operator’s view during debris extrusion (Fig. 3). Before the root canal filling material removal, the weight of each Eppendorf tube was determined with an analytical balance (AUW-220D, Shimadzu, Tokyo, Japan) to a precision of 10^-5 g, averaging three consecutive measurements (Fig. 4). Finally, the specimens were assorted into three random subgroups (n = 15 per subgroup) based on the root canal filling material removal method.

Fig. 3 Process of collecting apically extruded debris using Eppendorf tubes and a 27-gauge needle to equilibrate internal and external pressures

Fig. 4 Analytical balance used for weighing the Eppendorf tubes with precision up to 10^-5 g, showing the weighing process

Sample size calculation

The sample size was determined based on a power analysis to ensure the statistical validity of the results. Considering the variability observed in previous studies regarding the amount of apically extruded debris during endodontic retreatment, a power analysis was conducted using G*Power software. An effect size of 0.5, which is considered a medium effect size, was assumed for the analysis. To achieve a statistical power of 0.80 with an alpha level of 0.05, the analysis indicated that a minimum of 30 teeth per group would be required. Therefore, a total of 90 teeth were included in the study, divided equally among the three NiTi system groups. This sample size is expected to provide sufficient power to detect significant differences in the amount of apically extruded debris among the different retreatment techniques.

Reciproc group

Using the Reciproc R25 file (size 25,08 taper ) in the RECIPROC mode of the VDW Gold Reciproc endomotor (VDW, Münich, Germany) eliminated the root canal filling material. The Reciproc R25 file, employed in a slow in-and-out pecking movement with a 3-mm amplitude, was combined with a gentle apical pressure and brushing motion against the canal’s lateral walls. After every third pecking movement, the file was extracted for flute cleaning. The procedure continued until the WL was achieved. Subsequently, an apical preparation was executed using the R50 file (size 50,05 taper ).

PTUR group

Removal of the root canal filling material was accomplished using PTUR files D1 (size 30,09 taper ), D2 (size 25,08 taper ), and D3 (size 20,07 taper ), operating at 2-Ncm torque and 500-rpm speed. To reach the WL, the files were maneuvered with a brushing action in a crown-down orientation. Specifically, the D1 file addressed the cervical third, D2 was utilized in the middle third, and D3 covered the entire WL. The final apical preparation incorporated the ProTaper X5 file (size 50,06 taper ), operating at 2-Ncm torque and 300-rpm speed.

VDW.RotateR group

Using the VDW.RotateR file (size R25.05 taper) set at 3.5-Ncm torque and 400-rpm speed, the root canal filling material was effectively removed up to the WL. The concluding apical preparation employed the VDW.Rotate 50.04 file, working at 2-Ncm torque and 350-rpm speed.

A single operator executed all the procedures to ensure consistency and eliminate interoperator variability. While root canal filling material was removed, each canal was irrigated with 15 mL of distilled water and delivered through a 30-gauge double-sided port needle (Medical Brokers, Zgierz, Poland). After each use, the file flutes were meticulously cleaned. The removal process was determined to be complete once the following criteria were met: the final file had attained the new WL, no root canal filling material remained on the file, and the canal walls appeared clean and devoid of any visible debris.

Upon completion of the retreatment procedures, the tooth’s apical region was rinsed with 1 mL of distilled water to gather the debris that had extruded and adhered to the root apex, which was then collected in Eppendorf tubes. These tubes were subsequently placed in a 70 °C incubator for 5 days, allowing for the evaporation of any remaining distilled water. Following this, the dry weight of the extruded debris was measured. Utilizing the same analytical balance from earlier stages, each tube containing the debris was weighed thrice, from which an average value was derived. The net dry weight of the debris was then ascertained by subtracting the weight of an empty tube from that of a tube containing debris.

The time to remove the root canal filling material was diligently recorded using a chronometer. This duration encapsulated the period from the initial insertion of the instruments into the canal to reach the original WL. Pauses, such as when the instrument was removed from the canal, were accounted for by stopping and restarting the chronometer.

Measurement of extruded debris

Apically extruded debris was collected and weighed for each group. The amount of debris was measured using a high-precision microbalance. In addition, the time required for complete removal of gutta-percha and sealer was recorded using a stopwatch. Each NiTi system shaped/retreated a total of 30 canals, with 10 canals assigned to each of the three NiTi systems: PTUR, VDW.Rotate, and Reciproc. Each group utilized three files per canal according to the manufacturer’s instructions for each system.

Statistical analysis

The collected data were analyzed using appropriate statistical methods to determine significant differences between the groups in terms of the amount of extruded debris and retreatment time. Statistical analysis was performed using SPSS version 25.0 (IBM Corp., Armonk, NY, USA). Normality of data distribution was assessed using the Shapiro-Wilk test. For normally distributed data, a one-way analysis of variance, followed by Tukey’s post-hoc test, was used to compare the groups. For non-normally distributed data, the Kruskal-Wallis test, followed by Dunn’s post-hoc test, was employed. A p-value of less than 0.05 was considered statistically significant.

Results

Extrusion of debris by different file systems

Table 1 presents the data on the weight of apically extruded debris produced during retreatment across three file systems. The Reciproc file system recorded a mean value of 0.54 ± 0.24 mg (range, 0.11–1.21 mg). This was markedly higher, confirming that the Reciproc group significantly extruded more debris than its counterparts (p < 0.05). Precisely, the PTUR and VDW.RotateR systems demonstrated lower mean values of 0.28 ± 0.15 mg and 0.39 ± 0.29 mg, respectively. The extent of variability within each file system can be understood from the reported standard deviations with the VDW. The RotateR system has the highest variability. It is crucial to note that, based on the statistical annotations, the PTUR and VDW.RotateR groups were not significantly different regarding debris extrusion at the p = 0.05 level.

Table 1 Weight of apically extruded debris (mg)

File System	N	Min.	Max.	Mean ± S.D.	
Reciproc	30	0,11	1,21	0,54 ± 0,24a	
PTUR	30	0,03	0,63	0,28 ± 0,15b	
VDW.RotateR	30	0,05	1,02	0,39 ± 0,29b	
SD, standard deviation; Values with the same letters were not statistically different at p = 0 0.05

Extrusion of debris by different obturation techniques

Table 2 provides an overview of the amount of apically extruded debris during retreatment using two obturation techniques: SCT and CLC. The SCT exhibited a mean extrusion of 0.34 ± 0.23 mg, which was statistically lesser than the CLC technique, which had a mean of 0.46 ± 0.27 mg (p < 0.05). This indicates that the SCT is more conservative regarding debris extrusion than the CLC during retreatment.

Table 2 Weight of apically extruded debris (mg)

Obturation Technique	N	Min.	Max.	Mean ± S.D.	
SCT	45	0,03	0,96	0,34 ± 0,23A	
CLC	45	0,07	1,21	0,46 ± 0,27B	
CLC, cold lateral compaction; SD, standard deviation; SCT, single-cone technique;

Values with the same letters were not statistically different at p = 0.05

Retreatment Time for different obturation techniques

Table 3 shows a comparison of the duration required for retreatment across the obturation techniques. The findings suggest that SCT required a significantly shorter time, with a mean duration of 111.12 ± 33.46 s (range, 56.47–166.12 s). In contrast, the CLC technique took an average of 176.26 ± 52.26 s (range, 95.88–305.36 s) (p < 0.05). This highlights the efficiency of the SCT over the CLC in terms of time consumption during retreatment.

Table 3 Retreatment time (s)

Obturation Technique	N	Min.	Max.	Mean ± S.D.	
SCT	45	56,47	166,12	111,12 ± 33,46a	
CLC	45	95,88	305,36	176,26 ± 52,26b	
CLC, cold lateral compaction; SD, standard deviation; SCT, single-cone technique;

Values with the same letters were not statistically different at p = 0.05

Intragroup comparisons

Intragroup comparisons were performed to compare the results for SCT (n = 15) and CLC (n = 15) within each NiTi system:

Reciproc group

The SCT in the Reciproc group resulted in a mean debris extrusion of 0.50 ± 0.20 mg and required a mean retreatment time of 105.30 ± 30.20 s. In contrast, the CLC technique in the same group resulted in a mean debris extrusion of 0.58 ± 0.26 mg and required a mean retreatment time of 170.94 ± 55.20 s. The SCT resulted in significantly less debris and required significantly less time compared to the CLC technique (p < 0.05) (Table 4).

Table 4 Intragroup comparison for reciproc group

Measurement	Single Cone (SC) (n = 15)	Cold Lateral Compaction (CLC) (n = 15)	p-value	
Mean debris (mg)	0.50 ± 0.20	0.58 ± 0.26	< 0.05	
Mean retreatment time (s)	105.30 ± 30.20	170.94 ± 55.20	< 0.05	

PTUR group

The SCT in the PTUR group resulted in a mean debris extrusion of 0.26 ± 0.14 mg and required a mean retreatment time of 108.15 ± 32.40 s. In contrast, the CLC technique in the same group resulted in a mean debris extrusion of 0.30 ± 0.16 mg and required a mean retreatment time of 178.52 ± 50.30 s. There was no significant difference in debris extrusion between the SCT and CLC technique (p > 0.05). However, the SCT required significantly less time compared to the CLC technique (p < 0.05) (Table 5).

Table 5 Intragroup comparison for PTUR group

Measurement	Single Cone (SC) (n = 15)	Cold Lateral Compaction (CLC) (n = 15)	p-value	
Mean debris (mg)	0.26 ± 0.14	0.30 ± 0.16	> 0.05	
Mean retreatment time (s)	108.15 ± 32.40	178.52 ± 50.30	< 0.05	

VDW.rotate group

The SCT in the VDW.Rotate group resulted in a mean debris extrusion of 0.38 ± 0.28 mg and required a mean retreatment time of 120.40 ± 36.50 s. In contrast, the CLC technique in the same group resulted in a mean debris extrusion of 0.40 ± 0.30 mg and required a mean retreatment time of 179.32 ± 51.30 s. There was no significant difference in debris extrusion between the SCT and CLC technique (p > 0.05). However, the CLC technique required significantly less time compared to the SCT (p < 0.05) (Table 6).

Table 6 Intragroup comparison for VDW rotate group

Measurement	Single Cone (SC) (n = 15)	Cold Lateral Compaction (CLC) (n = 15)	p-value	
Mean debris (mg)	0.38 ± 0.28	0.40 ± 0.30	> 0.05	
Mean retreatment time (s)	120.40 ± 36.50	179.32 ± 51.30	< 0.05	

Discussion

Endodontic retreatment is a critical procedure aimed at resolving persistent or recurrent infections in previously treated teeth. The success of retreatment largely depends on the complete removal of the existing root canal filling material, thorough cleaning, reshaping of the root canal system, and effective final obturation [18]. However, a significant challenge during this process is the apical extrusion of debris, which can lead to postoperative discomfort as previously mentioned [19]. Various studies have documented this phenomenon in primary RCTs, emphasizing the need for effective techniques to minimize debris extrusion [13].

External inflammatory resorption, often associated with orthodontic treatments or trauma, primarily affects the apical region of the tooth [20]. Research indicates that maxillary central and lateral incisors are particularly susceptible to this condition, with incidences of 42.3% and 38.5%, respectively, while mandibular incisors are affected at a lower rate of 17.4% [21]. Given the higher susceptibility of maxillary incisors to EARR, these teeth were selected for the present study to ensure a relevant and focused investigation and to provide a robust model to examine the effects of different NiTi file systems on debris extrusion in a clinically relevant scenario. In addition, by focusing on teeth with a higher likelihood of external resorption, the study’s findings can be more effectively translated into clinical practice.

Previous studies have employed various methodologies to simulate apical root resorption and measure debris extrusion. Da Silveira et al. [22] suggested acid demineralization to create irregular resorption cavities, while others, such as Topcuoglu, standardized lesion creation by removing the apical 2 mm of the root using burs [23]. Furthermore, the simulation of periapical tissue resistance has been attempted using materials such as floral foam and agar gel [24]. However, despite their experimental value, these materials have some limitations; floral foam can absorb irrigant solutions and debris, and agar gel does not fully replicate the variable density of periapical tissues [25]. In this study, a standardized approach of removing the apical 2 mm of the root was used to ensure consistency and comparability of results. This method, consistent with previous research by Topçuoğlu et al. [23] and Da Silveira et al. [22], not only aligns with previous research but also enhances the reliability of the findings by providing a controlled environment to assess debris extrusion accurately.

Recent studies have explored the impact of different NiTi file systems on the extent of apically extruded debris. Gkampesi et al. [26] found that NiTi rotary retreatment files were effective in reducing debris extrusion compared to hand files. Karova and Zongova-Adem [27] also reported similar findings, highlighting the efficiency of rotary systems in minimizing apical extrusion. Furthermore, Serefoglu et al. [28] emphasized that the type of file system and the curvature of the root canal significantly influence the amount of extruded debris during retreatment procedures. These studies underscore the importance of selecting appropriate file systems to optimize clinical outcomes and reduce postoperative complications.

This study’s findings provide valuable insights into the clinical relevance of different NiTi file systems and obturation techniques. By evaluating three different NiTi file systems, the study provides a comparative analysis of their effects on apical debris extrusion, which can guide clinicians in selecting the most appropriate file system for endodontic retreatment. Understanding how obturation techniques influence debris extrusion can help clinicians minimize postoperative complications.

The study revealed several key findings regarding the extent of apically extruded debris during endodontic retreatment using three different NiTi file systems:

Reciproc File System: The Reciproc file system caused significantly more extruded debris compared to the PTUR and VDW.RotateR systems (p < 0.05). This suggests that the choice of file system can significantly influence the amount of debris extrusion, potentially affecting postoperative outcomes.

Obturation Techniques: The SCT resulted in significantly less debris extrusion than the CLC technique (p < 0.05). This finding highlights the importance of selecting the most appropriate obturation technique to minimize debris extrusion.

Retreatment Time: The total retreatment time showed no significant difference between the file systems (p > 0.05). However, it was significantly shorter in the SCT group compared to the CLC technique group (p < 0.05), indicating that the obturation technique can impact the efficiency of the retreatment procedure.

In light of these findings, the null hypothesis was rejected, underscoring the significance of the choice of file system and obturation technique in influencing the amount of apically extruded debris during retreatment.

These findings also align with and contrast various studies in the existing literature. For instance, consistent with Gkampesi et al.’s [26] study, we found that the Reciproc file system, a rotary system, caused significant debris extrusion, highlighting the need for careful selection of file systems to minimize postoperative complications.However, some studies, such as those by Topcuoglu et al. [23], reported less debris extrusion with Reciproc compared to other systems. These contrasting findings might be attributed to operator-related variables or differences in study design, highlighting the need for standardized protocols in future research. Similarly, Dinçer et al. [29] found that the Reciproc system exhibited the lowest apical extrusion of debris, which contrasts with our results. This discrepancy may be due to variations in the number of files employed in the respective studies. Such inconsistencies highlight the complexity of apical extrusion and suggest that further research is needed to establish more uniform methodologies and better understand the factors contributing to these differences.

Çanakçı et al. [30] extended the comparative examination to include the PTUR, MTwoR, D-Race, R-Endo, and Reciproc file systems. Their findings indicated that the Reciproc system extruded significantly more debris than the other groups, consistent with our study. In a separate investigation, Topçuoğlu et al. [31] evaluated the amount of apically extruded debris during the retreatment of root canals filled by three different filling techniques (CLC, wave vertical compaction, and SCT) using two distinct sealers (AH Plus and MTA Fillapex). They determined that the SCT group exhibited significantly less debris extrusion than the CLC group, consistent with our study.

Rödig et al. [7] compared the total time required for retreatment using hand files, Reciproc, and PTUR and found no statistically significant difference between Reciproc and PTUR. Similarly, Akbulut et al. [32]. compared the total time required for retreatment using hand files, Twisted File (TF) Adaptive, Reciproc, and PTUR and yielded no statistically significant difference between Reciproc and PTUR. Our findings align with those of these studies, confirming that the choice of file system does not significantly impact retreatment time. However, Özyürek et al. [33] investigated the total time required for retreatment using TF Adaptive, PTN, Reciproc, and PTUR and found that PTUR was significantly faster than the other groups.

Strengths and limitations

This study has several strengths that contribute to its scientific value and potential clinical impact. First, the standardization in creating apical resorption lesions by removing the apical 2 mm of the root using burs ensured consistency in lesion formation, enhancing the reliability of the results. Second, by evaluating three different NiTi file systems, the study provides a comparative analysis of their effects on apical debris extrusion, which can guide clinicians in selecting the most appropriate file system for endodontic retreatment. Third, the study examined the impact of different obturation techniques on apical debris extrusion, offering valuable insights for clinical practice. Understanding how obturation techniques influence debris extrusion can help clinicians minimize postoperative complications.

However, the study also has certain limitations that should be acknowledged. The involvement of different operators in the study may introduce variability in the results. Operator skills and experience can influence the effectiveness of the file systems used. Previous studies have highlighted the importance of operator consistency in endodontic procedures [34]. The study was conducted under laboratory conditions, which may not fully replicate clinical settings. The use of materials such as floral foam and agar gel to simulate periapical tissue resistance has limitations in accurately representing the variable density of actual periapical tissues [35]. Distilled water was used as the irrigation solution to prevent NaOCl crystallization. While this choice is methodologically sound, it limits the assessment of effects commonly observed with clinical irrigants such as NaOCl or EDTA, which are frequently used in endodontic treatments [36].

In clinical practice, retreatment procedures typically involve using files with apical diameters larger than the apical diameter of the master apical file used in the initial canal preparation, ensuring comprehensive removal of root canal filling material [37]. A previous study has highlighted the influence of the number of files on the amount of apically extruded debris [38]. In the present study, additional instrumentation was introduced using size 50 files and one file to replicate clinical conditions, especially since the apical diameter of the master apical file in the initial canal preparation was size 40. However, a potential limitation in the study is the variability in the taper of the final instruments among the groups due to standardized produced files in the systems used, which may introduce inconsistency in the experimental design. The standardized nature of the file systems used in the study might not fully account for differences in taper and size among the systems. This could impact the generalizability of the findings to clinical practice where such variations are common [25].

Despite these limitations, the study’s findings underscore important considerations for file system and obturation technique selection in clinical practice. Minimizing apical extrusion of debris is crucial for reducing postoperative discomfort and improving patient outcomes. Future research can build on these findings by developing standardized protocols and using simulations that more closely mimic clinical conditions to further validate these results.

Clinical implications and recommendations for future research

The findings of this study have several important implications for clinical practice. Minimizing apical extrusion of debris is crucial for reducing postoperative discomfort and improving patient outcomes. Clinicians should consider the choice of file system and obturation technique carefully during endodontic retreatment procedures. The study highlights that the Reciproc file system caused significantly more debris extrusion compared to the PTUR and VDW.RotateR systems. Therefore, clinicians might prefer PTUR or VDW.RotateR systems to minimize debris extrusion. In addition, the SCT resulted in less debris extrusion than the CLC technique, suggesting that the SCT might be a better option in clinical scenarios to reduce postoperative complications.

Furthermore, the study emphasizes the need for standardized protocols in clinical practice. Variability in operator skills and experience can influence the outcomes of endodontic retreatment, as highlighted in previous studies [34]. Standardized training and guidelines can help reduce this variability and improve the consistency and quality of endodontic treatments.

For future research, several areas can be explored to build on the findings of this study. First, further investigations could focus on evaluating the impact of different irrigants and irrigation techniques on apical debris extrusion. While this study used distilled water to prevent NaOCl crystallization, future studies could explore the effects of commonly used clinical irrigants such as NaOCl or EDTA to provide more clinically relevant insights [36].

Second, there is a need for more clinical studies that replicate real-world conditions more closely. Laboratory studies, while valuable, may not fully capture the complexities of clinical scenarios [35]. Future research should aim to include clinical trials that consider the full spectrum of clinical variables to validate and extend the findings of laboratory studies.

Finally, exploring the development of new file systems and obturation techniques that are specifically designed to minimize apical debris extrusion could be a valuable direction for future research. Innovations in endodontic technology could lead to improved patient outcomes and more efficient clinical procedures [25].

Conclusion

This study provides valuable insights into the factors influencing apical debris extrusion during endodontic retreatment. The findings indicate that the choice of NiTi file system and obturation technique significantly impacts the amount of apically extruded debris. Specifically, the Reciproc file system was associated with greater debris extrusion compared to the PTUR and VDW.RotateR systems, while the SCT resulted in less debris extrusion than the CLC technique.

Clinicians should carefully select file systems and obturation techniques to minimize postoperative complications. Standardized protocols and training are essential to reduce variability in clinical outcomes. Future research should explore the effects of different irrigants, root canal geometries, and clinical conditions to validate these findings and improve endodontic retreatment practices.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary Material 1

Author contributions

U. I: Project development, Data Collection, Manuscript writing Ç. B.M: Data analysis, Data Collection.

Funding

This study was supported by the Samsun Ondokuz Mayis University Research Fund (Project No: PYO.DIS.1904.20.007).

Data availability

Data is provided within the manuscript or supplementary information files. The datasets used and analyzed during the current study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

The Clinical Research Ethics Committee of Ondokuz Mayıs University approved the study protocol (2020/341).

Consent for publication

Not Applicable.

Informed consent

was obtained in written form from all study participant.

Competing interests

The authors declare no competing interests.

Abbreviations

CLC Cold lateral compaction

PTUR ProTaper Universal Retreatment

VDW.RotateR VDW.Rotate Retreatment

SCT Single-cone technique

EARR External apical root resorption

RCT Root canal treatment

NiTi Nickel-titanium

WL Working length

PTN ProTaper Next

NaOCl Sodium hypochlorite

EDTA Ethylenediamine tetra acetic acid

TF Twisted File

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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