Comparative Evaluation of Vertical Fracture Resistance and Retrieval Outcomes Using Ultrasonic, LeoPen Loop, and XP-Endo Shaper Systems: An In Vitro Study

Comparative Evaluation of Vertical Fracture Resistance and Retrieval Outcomes Using Ultrasonic, LeoPen Loop, and XP-Endo Shaper Systems: An In Vitro Study | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Comparative Evaluation of Vertical Fracture Resistance and Retrieval Outcomes Using Ultrasonic, LeoPen Loop, and XP-Endo Shaper Systems: An In Vitro Study Mariam Ahmed Mohamed, Nehal Nabil, Nermine Hassan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8090679/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 13 You are reading this latest preprint version Abstract Background Separated endodontic instruments are a frequent procedural challenge that can compromise treatment outcomes. Retrieval techniques vary in efficiency and may influence root integrity. This study compared the impact of three retrieval systems—ultrasonic tips, LeoPen loop, and XP-Endo Shaper—on vertical fracture resistance (VFR), retrieval time, and retrieval success. Methods Twenty-seven extracted human mandibular molars with moderately curved mesial roots (15–30°) were randomly allocated into three groups (n = 9): Ultrasonic Tip (Ed4), XP-Endo Shaper, and LeoPen Loop. A 4 mm NiTi fragment was fractured in the middle third of each canal. Retrieval was performed under magnification, and success (yes/no), retrieval time (min), and post-retrieval VFR (N) were measured using a universal testing machine. Data were analyzed using one-way ANOVA and Fisher’s exact test (α = 0.05). Results The LeoPen Loop system achieved the highest retrieval success (88.9%), followed by ultrasonics (66.7%), while the XP-Endo Shaper had the lowest (11.1%) (FEp = 0.001). Mean ± SD retrieval times were 25.4 ± 8.8 min, 24.0 ± 7.7 min, and 19.8 ± 5.6 min, respectively (p = 0.11). Mean ± SD VFR values were 711.8 ± 230.1 N (ultrasonic), 730.4 ± 241.0 N (XP-Endo Shaper file), and 710.0 ± 215.3 N (LeoPen), showing no significant differences (p = 0.95). A weak, non-significant correlation existed between retrieval time and VFR (r = − 0.13, p = 0.53). Conclusions All three systems preserved comparable vertical fracture resistance. The LeoPen Loop achieved the highest retrieval success with minimal complications, making it a reliable and conservative technique for removing separated instruments from moderately curved canals. Ultrasonic retrieval remains effective when applied carefully, whereas the XP-Endo Shaper demonstrated limited success in this context. instrument separation instrument retrieval ultrasonics wire and loop time Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Background Instrument separation is one of the most frustrating procedural accidents encountered during root canal therapy. The separated instrument can obstruct canal negotiation, limit cleaning and shaping, and compromise the quality of obturation. Ultimately, this may jeopardize the long-term success of root canal treatment, especially when the fragment is located beyond the canal curvature or apically( 1 ). The reported incidence of instrument separation ranges from 0.25% to 6%, depending on the type of alloy, design of the instrument, degree of canal curvature, and operator experience( 2 ). A variety of retrieval techniques have been proposed to manage this complication. Among these, ultrasonic systems remain widely used because they allow better visualization under the dental operating microscope (DOM) and loosen the fragment through controlled vibrations. However, excessive use of ultrasonic energy may result in undesirable dentin removal, ledge formation, or perforation( 3 ). Loop-based retrieval systems, such as the LeoPen and BTR-Pen, have been introduced as conservative alternatives that use a fine nitinol wire loop to engage and pull the fragment coronally with minimal canal enlargement( 4 ). Meanwhile, adaptive rotary systems, such as the XP-Endo Shaper, have been explored for instrument retrieval due to their ability to expand and unwind during rotation, theoretically facilitating engagement with the fractured segment. Yet, evidence regarding their retrieval effectiveness in complex root anatomies remains limited. Retrieval attempts inherently involve dentin removal to expose the separated fragment, potentially weakening the tooth and predisposing it to vertical root fracture (VRF). This catastrophic failure often leads to tooth extraction. Previous research has suggested that aggressive dentin removal significantly reduces fracture resistance ( 5 ). However, findings are inconsistent, and few studies have simultaneously compared retrieval success, procedural efficiency, and post-retrieval fracture resistance using multiple contemporary systems ( 6 , 7 ). The LeoPen loop system has been praised for its safety and minimal dentin sacrifice, yet quantitative data comparing its effect on VFR to other techniques are scarce. Similarly, although ultrasonics are well-established, the balance between retrieval efficiency and dentin preservation remains a concern. Conversely, the XP-Endo Shaper, primarily designed for canal shaping rather than retrieval, may impose additional torsional stress on dentin when adapted for fragment removal ( 8 ). Given the limited comparative evidence, this in vitro study aimed to evaluate and compare three retrieval techniques—ultrasonics, the LeoPen loop system, and the XP-Endo Shaper—in terms of vertical fracture resistance after retrieval, retrieval success, and retrieval time. The null hypothesis stated that there would be no significant differences among the three systems across the assessed parameters. Materials and Methods This study was carried out at the Faculty of Dentistry, Department of Endodontics, Cairo University, Egypt, with the approval of the Research Ethical Committee (REC) of the Faculty of Dentistry, Cairo University, which reviewed and approved the protocol for its scientific content and adherence to ethical standards. Approval number : 26-6-2023 Code : ENDO 3-3-3. Sample size calculation and selection A total of twenty-seven extracted adult human mandibular molars were used in this study. The extracted teeth were obtained from the dental hospital at the Faculty of Dentistry, Cairo University dental hospital, meeting the following criteria: fully developed apices and intact crowns and roots; no caries, cracks, or previous endodontic treatment; and root curvature between 15° and 30°, as determined using Schneider’s technique. The sample size was determined based on previous studies evaluating vertical fracture resistance following instrument retrieval ( 3 ), assuming an effect size of 0.35, α = 0.05, and power = 80%. Teeth with severe curvature (> 30°), root resorption, or open apices were excluded. Samples were cleaned and then stored in a 0.1% thymol solution. Canal preparation and creation of fractured instruments After access cavity preparation, samples were mechanically prepared using the Plex-V rotary NiTi files (Orodeka LTD, Jining City – Shandong Province, China) up to size 25, taper 4%, with 5.25% sodium hypochlorite (NaOCl) irrigation. A notch was made at 4 mm of the Mpro file (Innovative Material and Devices, Inc. (IMD), Jiangsu, P.R. China) with size #25 and a 6% taper, fracturing it in the middle third of the mesiobuccal canal. Teeth were then mounted in silicone molds with standardized vertical and horizontal positions. Grouping and retrieval procedures The samples were randomly divided into three equal groups (n = 9 each) according to the retrieval technique. Staging platform was created in all groups using using a modified Gates Glidden size two (MANI, INC. Industrial Park, Utsunomiya, Tochigi, Japan) then under the DOM as shown in Fig. 1, Troughing was performed by Ed4 ultrasonic tip (GuilinWoodpecker Medical Instrument Co., Ltd., China) using the VARIOS 370 scaler (NSK, Tochigi, Japan) with low power settings in pecking motions, exposing the coronal 2mm of the separated tip in 180 degrees. Figure (1) should be placed here Group I – Ultrasonic retrieval (control) Troughing was continued using the Ed4 ultrasonic tip, displayed in Fig. 2. The canal was kept wet with 17% EDTA to enhance cavitation and acoustic streaming, facilitating apical exposure of the fragment. Light intermittent strokes were applied until the fragment was dislodged. The retrieval attempt was considered successful if removal occurred within 45 minutes( 2 ). Failure was recorded if perforation occurred or retrieval was not achieved. Figure (2) should be placed here Group II – XP-Endo Shaper retrieval The XP-Endo Shaper (FKG Dentaire Sàrl, Le Crêt-du-Locle, Switzerland) was operated at 1000 rpm and 0.6 Ncm torque using an X-Smart Endo motor (Dentsply Maillefer, Ballaigues, Switzerland). As shown in Fig. 3, the file was inserted with light up-and-down strokes in the inner canal curvature, using 17% Ethylenediaminetetraacetic acid (EDTA) lubricant to reduce torsional stress and cyclic fatigue. Each attempt was limited to 45 minutes; failure was recorded if retrieval was not achieved, or if the XP-Endo Shaper fractured or displaced the segment apically( 1 ). Figure (3) should be placed here Group III – LeoPen loop retrieval Additional ultrasonic troughing was carried out in a counterclockwise motion, circumferentially allowing 360° exposure (~ 3 mm) as shown in Fig. 4 (A) until the fragment entered the “dancing stage” ( 9 ). A #40 plugger (Fanta Dental, Shanghai, China) was used to measure the created space, enabling selection of a 0.4 mm working tip with a 0.1 mm nitinol loop (LeoPen, LeoDent, China). The loop was tightened over the fragment displayed in Fig. 4 (B), then gentle lateral swaying and coronal traction were performed. Failure was recorded if engagement was not possible after several attempts, if more than 45 minutes elapsed, or if perforation occurred. Figure (4) picture (A) and (B) should be placed here Preparation for fracture resistance testing Following retrieval, all samples were coded and blinded for testing. Samples were decoronated and sectioned using an IsoMet 4000 precision saw (Buehler, Leinfelden-Echterdingen, Germany), retaining only the mesial root for testing. A 0.2 mm layer of polyether impression material was applied to each specimen and embedded in self-curing acrylic resin blocks, leaving 2 mm of the specimen exposed above the resin. After complete setting of the material, each specimen was mounted on an Instron Universal Testing Machine (Model 3345, Instron, Norwood, Massachusetts, USA). A stainless-steel ball (2.5 mm radius) applied an axial compressive load at a speed of 1 mm/min until fracture occurred (Fig. 5). The maximum load (N) required to fracture each root was recorded, and all data were tabulated for statistical analysis. Fractured specimens were then examined under a stereomicroscope (XCAM 1080P8MPB) at 30× magnification to analyze the fracture patterns. Figure (5) should be placed here Statistical analysis All data were analyzed using SPSS version 25.0 (IBM Corp., USA). Data normality was tested using the Shapiro–Wilk test. VFR and retrieval time were expressed as mean ± standard deviation (SD) and compared using one-way ANOVA with Tukey’s post hoc test. Retrieval success was analyzed using Fisher’s Exact Test. Correlation between retrieval time and VFR was determined using Pearson’s correlation coefficient. The level of significance was set at p ≤ 0.05. Results Table 1 presents the mean retrieval time and fracture resistance among the three tested retrieval techniques. The XP-Endo Shaper group recorded the shortest mean retrieval time (19.78 ± 5.60 min), while the LeoPen loop required the longest (25.44 ± 8.84 min). The ultrasonic group demonstrated an intermediate duration (24.04 ± 7.70 min). Although the XP-Endo Shaper appeared faster, the difference did not reach statistical significance (F = 2.37, p = 0.11, η² = 0.165). Regarding vertical fracture resistance (VFR), all three techniques yielded comparable mean values—711.76 ± 230.13 N for Ultrasonic, 730.35 ± 241.04 N for XP-Endo Shaper, and 710.00 ± 215.26 N for LeoPen loop—with no significant difference detected (F = 0.051, p = 0.95, η² = 0.004). These results indicate that none of the retrieval methods compromised root strength, and procedural differences in timing did not translate into measurable structural changes. Table (1) should be placed here Figure 6 summarizes the failure mode distribution between the studied groups. The vertical fracture pattern was the most frequent overall (66.7% of samples), particularly prevalent in the LeoPen group (88.9%), followed by ultrasonic (66.7%) and XP-Endo Shaper (44.4%). Combined fractures (vertical + horizontal) occurred in 29.6% of specimens, while combined vertical + oblique fractures were rare (3.7%). No horizontal or oblique fractures alone were observed. Statistical comparison revealed no significant difference among groups for any fracture type (p > 0.05), suggesting that the retrieval technique did not influence the failure mode. Figure (6) should be placed here Table 2 shows the distribution of successful versus failed retrievals and the reasons for failure. The LeoPen loop group achieved the highest retrieval success (88.9%), followed by the ultrasonic group (66.7%). In contrast, the XP-Endo Shaper demonstrated a markedly lower success rate (11.1%) with significant intergroup variation (FE p = 0.001*). Most failures in the XP-Endo group were due to fracture of the XP file itself (62.5%) or apical displacement of the separated segment. In contrast, failures in the ultrasonic group were primarily perforations (66.7%), whereas the LeoPen group had only one minor failure. The comparison of failure reasons showed a statistically significant difference (p = 0.034*), indicating that retrieval system design influences both the success rate and the mode of procedural failure. Clinically, these results suggest that the LeoPen loop system offers a safer, more predictable approach to managing separated instruments. Table (2) should be placed here Correlation analysis demonstrated a weak, non-significant negative correlation between retrieval tie and VFR (r = − 0.13, p = 0.53) as shown in Fig. 7. This indicates that longer retrieval duration did not reduce fracture resistance, implying that extended but careful instrumentation—such as with the LeoPen loop—does not weaken root structure. Figure (7) should be placed here Discussion Instrument separation is a frequent procedural complication in endodontics, particularly with NiTi instruments( 10 ). This event jeopardizes treatment prognosis, necessitating effective orthograde management techniques such as retrieval or bypass( 11 ). However, retrieval attempts inevitably remove dentin, increasing the risk of vertical root fracture( 12 ). Therefore, any retrieval strategy must balance efficiency with dentin preservation, as excessive dentin removal remains a principal cause of structural failure( 3 , 13 ). The present randomized in-vitro study compared three retrieval systems—ultrasonics, XP-Endo Shaper, and the LeoPen loop device—regarding vertical fracture resistance (VFR), retrieval success, and time. The model used standardized curvature (15°–30°) in mandibular mesiobuccal roots, controlled instrument length of 4 mm, and consistent canal preparation and irrigation protocols. The Universal Testing Machine was employed to measure fracture resistance, ensuring reproducibility and comparability with prior work( 14 , 15 ). The present results revealed no significant differences in fracture resistance among the three retrieval methods. This agrees with Abdeen et al. (2023)( 5 ) and contradicts Fu et al. (2019) ( 3 ), who observed reduced strength following ultrasonic retrieval in thinner roots. The difference reflects the use of molars in the current study, which possess thicker dentinal walls and greater tolerance to ultrasonic manipulation. Similarly, while Dulundu & Helvacioglu-Yigit (2022) reported reduced fracture resistance with loop devices, the current findings showed that LeoPen maintained root integrity comparable to ultrasonics—possibly due to its smaller loop diameter and more conservative troughing ( 4 ). The XP-Endo Shaper demonstrated VFR values equivalent to those of the other techniques, supporting reports that its adaptive MaxWire alloy minimizes outward dentinal stress( 16 ). Collectively, these findings confirm that all three systems can safely retrieve fractured instruments without compromising root strength. A marked difference emerged in retrieval success: LeoPen (88.9%) > Ultrasonic (66.7%) > XP-Endo Shaper (11.1%). LeoPen’s flexible nitinol loop achieved secure engagement with minimal dentin loss, consistent with prior results for similar loop systems( 5 , 17 ). Ultrasonics performed moderately well but carried a risk of perforation, corroborating Portela et al. (2022)( 18 ). The XP-Endo Shaper’s poor success was mainly due to instrument re-fracture, a problem previously noted in curved canals( 19 ). Although the XP-Endo Shaper achieved the shortest mean retrieval time, this was clinically meaningless given its high failure rate. Conversely, LeoPen required slightly more time but produced the most predictable and safe results( 18 ). The absence of correlation between retrieval time and VFR (r = − 0.13, p > 0.05) further confirms that longer procedures do not inherently weaken roots when performed carefully. In our study, most samples exhibited vertical fractures, consistent across groups, with no significant intergroup differences. This pattern mirrors the typical stress distribution observed in endodontically treated molars under axial loading( 13 ). The lack of difference among systems implies that the retrieval technique affects the success rate more than the fracture mode. Conclusion Within the limitations of this in-vitro study, all three retrieval systems—Ultrasonic tip, XP-Endo Shaper, and LeoPen loop—demonstrated comparable vertical fracture resistance of mandibular molar roots, indicating that none of the techniques significantly weakened the tooth structure. However, apparent differences were observed in retrieval success rates, with the LeoPen loop achieving the highest, followed by Ultrasonic, and XP-Endo Shaper showing the lowest. Although the XP-Endo Shaper provided shorter retrieval times, this efficiency was offset by frequent re-fracture and procedural failure. Accordingly, the null hypothesis was accepted for fracture resistance but rejected for retrieval success, confirming that the choice of technique strongly affects clinical outcome while maintaining root integrity. Clinical Significance Successful removal of separated instruments must balance efficiency, safety, and dentin preservation. This study demonstrates that loop-based retrieval systems, such as LeoPen, offer a predictable, conservative, and structurally safe approach for managing fractured instruments in curved molar canals. Ultrasonic retrieval remains effective for accessible fragments but carries a moderate risk of perforation. In contrast, XP-Endo Shaper is not recommended as a standalone retrieval method due to its high failure tendency. Clinicians should therefore prioritize controlled, magnified retrieval over speed to ensure long-term tooth survival. Abbreviations DOM: dental operating microscope EDTA: Ethylenediaminetetraacetic acid Min: minute N: newton NaOCl: sodium hypochlorite REC: Research Ethical Committee SD: standard deviation VFR: vertical fracture resistance VRF: vertical root fracture Declarations Ethics Approval and Consent to Participate This study was conducted in full alignment with the principles of the Declaration of Helsinki. Ethical approval was obtained from the Research Ethics Committee, Faculty of Dentistry, Cairo University, under approval number 26-6-2023. As this was an in vitro study that did not involve human participants, the Committee deemed informed consent unnecessary. Consent for Publication Not applicable. Availability of Data and Materials The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request. All experimental data, measurement tables, and statistical analysis files supporting the conclusions of this article are stored at the Faculty of Dentistry, Cairo University, and can be provided in anonymized form upon request. Competing Interests The author declares that there are no competing interests. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Author’s Contributions M.A. conceived and designed the study, performed the experiments, analyzed the data, and wrote the manuscript. N.N. research planning, designing, research execution, and data monitoring. Contributed statistical analysis of the results, wrote the research report, and the article to be published. N.H. Sequence generation, allocation concealment, randomization, data management, and proofreading the manuscript. References Terauchi Y, O'Leary L, Suda H. Removal of separated files from root canals with a new file-removal system: Case reports. Journal of endodontics. 2006;32(8):789-97. Shahabinejad H, Ghassemi A, Pishbin L, Shahravan A. Success of ultrasonic technique in removing fractured rotary nickel-titanium endodontic instruments from root canals and its effect on the required force for root fracture. Journal of endodontics. 2013;39(6):824-8. Fu M, Huang X, Zhang K, Hou B. Effects of Ultrasonic Removal of Fractured Files from the Middle Third of Root Canals on the Resistance to Vertical Root Fracture. Journal of endodontics. 2019;45(11):1365-70. Dulundu M, Helvacioglu-Yigit D. The Efficiency of the BTR-Pen System in Removing Different Types of Broken Instruments from Root Canals and Its Effect on the Fracture Resistance of Roots. Materials (Basel, Switzerland). 2022;15(17). Abdeen MA, Plotino G, Hassanien EE, Turky M. Evaluation of Dentine Structure Loss after Separated File Retrieval by Three Different Techniques: An Ex-vivo Study. European endodontic journal. 2023;8(3):225-30. Pruthi PJ, Nawal RR, Talwar S, Verma M. Comparative evaluation of the effectiveness of ultrasonic tips versus the Terauchi file retrieval kit for the removal of separated endodontic instruments. Restorative dentistry & endodontics. 2020;45(2):e14. Lobo WMV, Sayed A, Sapkale K, Ramugade M, Benavides ACM. A comparative evaluation of the resistance to vertical root fracture after removal of separated instruments using three instrument retrieval systems: An in vitro study. Journal of conservative dentistry and endodontics. 2025;28(2):182-6. Mahale VD, Saxena T, Sharma S, Mohan EA. Quantitative analysis of troughing depth for successful instrument retrieval using the loop technique: A cross-sectional in vivo study. Journal of conservative dentistry and endodontics. 2025;28(4):360-5. Shajahan S, Dhanavel C, Raja SV, Sornamalar M, Balavaishnavi G. Comparative Evaluation of the Efficiency in Retrieving Separated Reciprocating Instruments Using Three Different File Retrieval Systems in Maxillary First Molars: An In Vitro Study. Journal of pharmacy & bioallied sciences. 2024;16(Suppl 5):S4544-s7. Eskibağlar M, Özata MY, Ocak MS, Öztekin F. Investigation of fracture prevalence of instruments used in root canal treatments at a faculty of dentistry: a prospective study. Restorative dentistry & endodontics. 2023;48(4):e38. Garrocho A, Sánchez-Reynoso A, Berber MA, Ruiz-Rodríguez M, Pozos-Guillén A. Clinical Management of Intra-Pulp Canal Broken Endodontic Files in Primary Teeth: Literature Review. Odovtos - International Journal of Dental Sciences. 2020;23:16-20. Barakat F, Attia M. Effect of Two Techniques of Separated File Removal Systems on Dentin Loss and Fracture Resistance of Teeth (In Vitro Study). Egyptian Dental Journal. 2024;70:2877-84. Silva E, Lima CO, Barbosa AFA, Augusto CM, Souza EM, Lopes RT, et al. Preserving dentine in minimally invasive access cavities does not strength fracture resistance of restored mandibular molars. International endodontic journal. 2021;54(6):966-74. Madarati AA, Qualtrough AJ, Watts DC. Vertical fracture resistance of roots after ultrasonic removal of fractured instruments. International endodontic journal. 2010;43(5):424-9. Yassa S, Nabeel M, Ghobashy A, Alkhawas M. Fracture resistance and volumetric dentin change after management of broken instrument using static navigation – An in vitro study. Journal of conservative dentistry and endodontics. 2025;28:319-24. Uslu G, Özyürek T, Yılmaz K, Gündoğar M, Plotino G. Apically Extruded Debris during Root Canal Instrumentation with Reciproc Blue, HyFlex EDM, and XP-endo Shaper Nickel-titanium Files. Journal of endodontics. 2018;44(5):856-9. Jitesh S, Surendran S, Natanasabapathy V. Efficacy of two instrument retrieval techniques in removing separated rotary and reciprocating nickel-titanium files in mandibular molars - An in vitro study. Journal of conservative dentistry and endodontics. 2024;27(12):1240-5. Portela NN, Rech JP, Marchionatti AME, Barasuol JC. Techniques to address fractured instruments in the middle or apical third of the root canal in human permanent teeth: a systematic review of the in vitro studies. Clinical oral investigations. 2022;26(1):131-9. Jamleh A, Albanyan H, Alaqla A, Alissa H, Alshetan N, Alraffa S, et al. Impact of cooling on shaping ability of thermally treated files in canal models with double curvature. PeerJ. 2023;11:e15830. Tables Tables 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8090679","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":566376166,"identity":"7cf11c07-029d-40a8-a6de-d90d8c041233","order_by":0,"name":"Mariam Ahmed 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18:57:49","extension":"html","order_by":21,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78867,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/bfb260451341d00a7a47647b.html"},{"id":99318356,"identity":"281f30b5-ed4f-4d40-9327-d1202735571c","added_by":"auto","created_at":"2025-12-31 16:32:53","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":135621,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eBefore and after staging platform\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/2aa5df90961d5814037e5dcc.png"},{"id":99179798,"identity":"71571e5e-b3bd-464a-81a7-4dac0fdb17f3","added_by":"auto","created_at":"2025-12-29 18:57:48","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":84020,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eUltrasonic troughing\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/1263b20a57a697d05542dbe9.png"},{"id":99179797,"identity":"4f040d18-3dd1-4c24-b44d-599aed5c447f","added_by":"auto","created_at":"2025-12-29 18:57:48","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":81806,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eXP-Endo shaper file in the space between the broken file and the inner dentinal wall\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/9123cfad764a979fa417c397.png"},{"id":99317178,"identity":"705c9b3d-d1b7-49e7-9df9-9c645921d05c","added_by":"auto","created_at":"2025-12-31 16:29:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":199389,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(A) 360 degrees troughing around the head of the separated file \u003cbr\u003e\n(B) LeoPen Loop around the head of the separated file\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/fd54e2af40505be1e283f3b1.png"},{"id":99316227,"identity":"8b27ac76-26e1-429b-b3b5-c90fda1eb6c9","added_by":"auto","created_at":"2025-12-31 16:27:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":436621,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFracture of the specimen after applying the force\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/48e72f8d9dc661a658638023.png"},{"id":99179805,"identity":"e0f0574b-06a7-4a3e-92ff-7a2b649f5b15","added_by":"auto","created_at":"2025-12-29 18:57:48","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":21423,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eBar chart shows the mode of failure according to fracture direction\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/a457124c58772d214d509055.png"},{"id":99179808,"identity":"0ba40998-2548-4430-922e-69a1bd3d807a","added_by":"auto","created_at":"2025-12-29 18:57:48","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":40457,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScatter plot represents the correlation between vertical fracture resistance and retrieval time\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/fa0142ad30506f23610ec031.png"},{"id":99323705,"identity":"228fdde3-589a-499d-8744-878b7c2510ef","added_by":"auto","created_at":"2025-12-31 16:46:03","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2413672,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/0e0f7679-04ef-495b-9ec3-571b357ab160.pdf"},{"id":99179801,"identity":"a65a75fc-bc57-4cd2-9b40-67de5f628d81","added_by":"auto","created_at":"2025-12-29 18:57:48","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":16836,"visible":true,"origin":"","legend":"","description":"","filename":"Tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-8090679/v1/9e16430864a63db9e7200532.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparative Evaluation of Vertical Fracture Resistance and Retrieval Outcomes Using Ultrasonic, LeoPen Loop, and XP-Endo Shaper Systems: An In Vitro Study","fulltext":[{"header":"Background","content":"\u003cp\u003eInstrument separation is one of the most frustrating procedural accidents encountered during root canal therapy. The separated instrument can obstruct canal negotiation, limit cleaning and shaping, and compromise the quality of obturation. Ultimately, this may jeopardize the long-term success of root canal treatment, especially when the fragment is located beyond the canal curvature or apically(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The reported incidence of instrument separation ranges from 0.25% to 6%, depending on the type of alloy, design of the instrument, degree of canal curvature, and operator experience(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). A variety of retrieval techniques have been proposed to manage this complication. Among these, ultrasonic systems remain widely used because they allow better visualization under the dental operating microscope (DOM) and loosen the fragment through controlled vibrations. However, excessive use of ultrasonic energy may result in undesirable dentin removal, ledge formation, or perforation(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e). Loop-based retrieval systems, such as the LeoPen and BTR-Pen, have been introduced as conservative alternatives that use a fine nitinol wire loop to engage and pull the fragment coronally with minimal canal enlargement(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Meanwhile, adaptive rotary systems, such as the XP-Endo Shaper, have been explored for instrument retrieval due to their ability to expand and unwind during rotation, theoretically facilitating engagement with the fractured segment. Yet, evidence regarding their retrieval effectiveness in complex root anatomies remains limited.\u003c/p\u003e \u003cp\u003eRetrieval attempts inherently involve dentin removal to expose the separated fragment, potentially weakening the tooth and predisposing it to vertical root fracture (VRF). This catastrophic failure often leads to tooth extraction. Previous research has suggested that aggressive dentin removal significantly reduces fracture resistance (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e). However, findings are inconsistent, and few studies have simultaneously compared retrieval success, procedural efficiency, and post-retrieval fracture resistance using multiple contemporary systems (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe LeoPen loop system has been praised for its safety and minimal dentin sacrifice, yet quantitative data comparing its effect on VFR to other techniques are scarce. Similarly, although ultrasonics are well-established, the balance between retrieval efficiency and dentin preservation remains a concern. Conversely, the XP-Endo Shaper, primarily designed for canal shaping rather than retrieval, may impose additional torsional stress on dentin when adapted for fragment removal (\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e). Given the limited comparative evidence, this in vitro study aimed to evaluate and compare three retrieval techniques\u0026mdash;ultrasonics, the LeoPen loop system, and the XP-Endo Shaper\u0026mdash;in terms of vertical fracture resistance after retrieval, retrieval success, and retrieval time. The null hypothesis stated that there would be no significant differences among the three systems across the assessed parameters.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThis study was carried out at the Faculty of Dentistry, Department of Endodontics, Cairo University, Egypt, with the approval of the Research Ethical Committee (REC) of the Faculty of Dentistry, Cairo University, which reviewed and approved the protocol for its scientific content and adherence to ethical standards. \u003cb\u003eApproval number\u003c/b\u003e: 26-6-2023\u0026emsp;\u0026emsp;\u003cb\u003eCode\u003c/b\u003e: ENDO 3-3-3.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSample size calculation and selection\u003c/h2\u003e \u003cp\u003eA total of twenty-seven extracted adult human mandibular molars were used in this study.\u003c/p\u003e \u003cp\u003eThe extracted teeth were obtained from the dental hospital at the Faculty of Dentistry, Cairo University dental hospital, meeting the following criteria: fully developed apices and intact crowns and roots; no caries, cracks, or previous endodontic treatment; and root curvature between 15\u0026deg; and 30\u0026deg;, as determined using Schneider\u0026rsquo;s technique. The sample size was determined based on previous studies evaluating vertical fracture resistance following instrument retrieval (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), assuming an effect size of 0.35, α\u0026thinsp;=\u0026thinsp;0.05, and power\u0026thinsp;=\u0026thinsp;80%. Teeth with severe curvature (\u0026gt;\u0026thinsp;30\u0026deg;), root resorption, or open apices were excluded. Samples were cleaned and then stored in a 0.1% thymol solution.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCanal preparation and creation of fractured instruments\u003c/h3\u003e\n\u003cp\u003eAfter access cavity preparation, samples were mechanically prepared using the Plex-V rotary NiTi files (Orodeka LTD, Jining City \u0026ndash; Shandong Province, China) up to size 25, taper 4%, with 5.25% sodium hypochlorite (NaOCl) irrigation. A notch was made at 4 mm of the Mpro file (Innovative Material and Devices, Inc. (IMD), Jiangsu, P.R. China) with size #25 and a 6% taper, fracturing it in the middle third of the mesiobuccal canal. Teeth were then mounted in silicone molds with standardized vertical and horizontal positions.\u003c/p\u003e\n\u003ch3\u003eGrouping and retrieval procedures\u003c/h3\u003e\n\u003cp\u003eThe samples were randomly divided into three equal groups (n\u0026thinsp;=\u0026thinsp;9 each) according to the retrieval technique. Staging platform was created in all groups using using a modified Gates Glidden size two (MANI, INC. Industrial Park, Utsunomiya, Tochigi, Japan) then under the DOM as shown in Fig.\u0026nbsp;1, Troughing was performed by Ed4 ultrasonic tip (GuilinWoodpecker Medical Instrument Co., Ltd., China) using the VARIOS 370 scaler (NSK, Tochigi, Japan) with low power settings in pecking motions, exposing the coronal 2mm of the separated tip in 180 degrees.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (1) should be placed here\u003c/b\u003e \u003c/p\u003e\n\u003ch3\u003eGroup I – Ultrasonic retrieval (control)\u003c/h3\u003e\n\u003cp\u003eTroughing was continued using the Ed4 ultrasonic tip, displayed in Fig.\u0026nbsp;2. The canal was kept wet with 17% EDTA to enhance cavitation and acoustic streaming, facilitating apical exposure of the fragment. Light intermittent strokes were applied until the fragment was dislodged.\u003c/p\u003e \u003cp\u003eThe retrieval attempt was considered successful if removal occurred within 45 minutes(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Failure was recorded if perforation occurred or retrieval was not achieved.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (2) should be placed here\u003c/b\u003e \u003c/p\u003e\n\u003ch3\u003eGroup II – XP-Endo Shaper retrieval\u003c/h3\u003e\n\u003cp\u003eThe XP-Endo Shaper (FKG Dentaire S\u0026agrave;rl, Le Cr\u0026ecirc;t-du-Locle, Switzerland) was operated at 1000 rpm and 0.6 Ncm torque using an X-Smart Endo motor (Dentsply Maillefer, Ballaigues, Switzerland). As shown in Fig.\u0026nbsp;3, the file was inserted with light up-and-down strokes in the inner canal curvature, using 17% Ethylenediaminetetraacetic acid (EDTA) lubricant to reduce torsional stress and cyclic fatigue. Each attempt was limited to 45 minutes; failure was recorded if retrieval was not achieved, or if the XP-Endo Shaper fractured or displaced the segment apically(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (3) should be placed here\u003c/b\u003e \u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eGroup III \u0026ndash; LeoPen loop retrieval\u003c/h2\u003e \u003cp\u003eAdditional ultrasonic troughing was carried out in a counterclockwise motion, circumferentially allowing 360\u0026deg; exposure (~\u0026thinsp;3 mm) as shown in Fig.\u0026nbsp;4 (A) until the fragment entered the \u0026ldquo;dancing stage\u0026rdquo; (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). A #40 plugger (Fanta Dental, Shanghai, China) was used to measure the created space, enabling selection of a 0.4 mm working tip with a 0.1 mm nitinol loop (LeoPen, LeoDent, China). The loop was tightened over the fragment displayed in Fig.\u0026nbsp;4 (B), then gentle lateral swaying and coronal traction were performed. Failure was recorded if engagement was not possible after several attempts, if more than 45 minutes elapsed, or if perforation occurred.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (4) picture (A) and (B) should be placed here\u003c/b\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003ePreparation for fracture resistance testing\u003c/h3\u003e\n\u003cp\u003eFollowing retrieval, all samples were coded and blinded for testing. Samples were decoronated and sectioned using an IsoMet 4000 precision saw (Buehler, Leinfelden-Echterdingen, Germany), retaining only the mesial root for testing. A 0.2 mm layer of polyether impression material was applied to each specimen and embedded in self-curing acrylic resin blocks, leaving 2 mm of the specimen exposed above the resin. After complete setting of the material, each specimen was mounted on an Instron Universal Testing Machine (Model 3345, Instron, Norwood, Massachusetts, USA). A stainless-steel ball (2.5 mm radius) applied an axial compressive load at a speed of 1 mm/min until fracture occurred (Fig.\u0026nbsp;5). The maximum load (N) required to fracture each root was recorded, and all data were tabulated for statistical analysis. Fractured specimens were then examined under a stereomicroscope (XCAM 1080P8MPB) at 30\u0026times; magnification to analyze the fracture patterns.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (5) should be placed here\u003c/b\u003e \u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eAll data were analyzed using SPSS version 25.0 (IBM Corp., USA).\u003c/p\u003e \u003cp\u003eData normality was tested using the Shapiro\u0026ndash;Wilk test. VFR and retrieval time were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD) and compared using one-way ANOVA with Tukey\u0026rsquo;s post hoc test. Retrieval success was analyzed using Fisher\u0026rsquo;s Exact Test. Correlation between retrieval time and VFR was determined using Pearson\u0026rsquo;s correlation coefficient. The level of significance was set at p\u0026thinsp;\u0026le;\u0026thinsp;0.05.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eTable\u0026nbsp;1 presents the mean retrieval time and fracture resistance among the three tested retrieval techniques. The XP-Endo Shaper group recorded the shortest mean retrieval time (19.78\u0026thinsp;\u0026plusmn;\u0026thinsp;5.60 min), while the LeoPen loop required the longest (25.44\u0026thinsp;\u0026plusmn;\u0026thinsp;8.84 min). The ultrasonic group demonstrated an intermediate duration (24.04\u0026thinsp;\u0026plusmn;\u0026thinsp;7.70 min). Although the XP-Endo Shaper appeared faster, the difference did not reach statistical significance (F\u0026thinsp;=\u0026thinsp;2.37, p\u0026thinsp;=\u0026thinsp;0.11, η\u0026sup2; = 0.165).\u003c/p\u003e \u003cp\u003eRegarding vertical fracture resistance (VFR), all three techniques yielded comparable mean values\u0026mdash;711.76\u0026thinsp;\u0026plusmn;\u0026thinsp;230.13 N for Ultrasonic, 730.35\u0026thinsp;\u0026plusmn;\u0026thinsp;241.04 N for XP-Endo Shaper, and 710.00\u0026thinsp;\u0026plusmn;\u0026thinsp;215.26 N for LeoPen loop\u0026mdash;with no significant difference detected (F\u0026thinsp;=\u0026thinsp;0.051, p\u0026thinsp;=\u0026thinsp;0.95, η\u0026sup2; = 0.004). These results indicate that none of the retrieval methods compromised root strength, and procedural differences in timing did not translate into measurable structural changes.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTable\u0026nbsp;(1) should be placed here\u003c/b\u003e \u003c/p\u003e \u003cp\u003eFigure 6 summarizes the failure mode distribution between the studied groups.\u003c/p\u003e \u003cp\u003eThe vertical fracture pattern was the most frequent overall (66.7% of samples), particularly prevalent in the LeoPen group (88.9%), followed by ultrasonic (66.7%) and XP-Endo Shaper (44.4%). Combined fractures (vertical\u0026thinsp;+\u0026thinsp;horizontal) occurred in 29.6% of specimens, while combined vertical\u0026thinsp;+\u0026thinsp;oblique fractures were rare (3.7%). No horizontal or oblique fractures alone were observed. Statistical comparison revealed no significant difference among groups for any fracture type (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05), suggesting that the retrieval technique did not influence the failure mode.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (6) should be placed here\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;2 shows the distribution of successful versus failed retrievals and the reasons for failure. The LeoPen loop group achieved the highest retrieval success (88.9%), followed by the ultrasonic group (66.7%). In contrast, the XP-Endo Shaper demonstrated a markedly lower success rate (11.1%) with significant intergroup variation (FE p\u0026thinsp;=\u0026thinsp;0.001*). Most failures in the XP-Endo group were due to fracture of the XP file itself (62.5%) or apical displacement of the separated segment.\u003c/p\u003e \u003cp\u003eIn contrast, failures in the ultrasonic group were primarily perforations (66.7%), whereas the LeoPen group had only one minor failure. The comparison of failure reasons showed a statistically significant difference (p\u0026thinsp;=\u0026thinsp;0.034*), indicating that retrieval system design influences both the success rate and the mode of procedural failure. Clinically, these results suggest that the LeoPen loop system offers a safer, more predictable approach to managing separated instruments.\u003c/p\u003e \u003cp\u003e \u003cb\u003eTable\u0026nbsp;(2) should be placed here\u003c/b\u003e \u003c/p\u003e \u003cp\u003eCorrelation analysis demonstrated a weak, non-significant negative correlation between retrieval tie and VFR (r = \u0026minus;\u0026thinsp;0.13, p\u0026thinsp;=\u0026thinsp;0.53) as shown in Fig.\u0026nbsp;7. This indicates that longer retrieval duration did not reduce fracture resistance, implying that extended but careful instrumentation\u0026mdash;such as with the LeoPen loop\u0026mdash;does not weaken root structure.\u003c/p\u003e \u003cp\u003e \u003cb\u003eFigure (7) should be placed here\u003c/b\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eInstrument separation is a frequent procedural complication in endodontics, particularly with NiTi instruments(\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e). This event jeopardizes treatment prognosis, necessitating effective orthograde management techniques such as retrieval or bypass(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). However, retrieval attempts inevitably remove dentin, increasing the risk of vertical root fracture(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e). Therefore, any retrieval strategy must balance efficiency with dentin preservation, as excessive dentin removal remains a principal cause of structural failure(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe present randomized in-vitro study compared three retrieval systems\u0026mdash;ultrasonics, XP-Endo Shaper, and the LeoPen loop device\u0026mdash;regarding vertical fracture resistance (VFR), retrieval success, and time. The model used standardized curvature (15\u0026deg;\u0026ndash;30\u0026deg;) in mandibular mesiobuccal roots, controlled instrument length of 4 mm, and consistent canal preparation and irrigation protocols. The Universal Testing Machine was employed to measure fracture resistance, ensuring reproducibility and comparability with prior work(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe present results revealed no significant differences in fracture resistance among the three retrieval methods. This agrees with Abdeen et al. (2023)(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) and contradicts Fu et al. (2019) (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e), who observed reduced strength following ultrasonic retrieval in thinner roots. The difference reflects the use of molars in the current study, which possess thicker dentinal walls and greater tolerance to ultrasonic manipulation. Similarly, while Dulundu \u0026amp; Helvacioglu-Yigit (2022) reported reduced fracture resistance with loop devices, the current findings showed that LeoPen maintained root integrity comparable to ultrasonics\u0026mdash;possibly due to its smaller loop diameter and more conservative troughing (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). The XP-Endo Shaper demonstrated VFR values equivalent to those of the other techniques, supporting reports that its adaptive MaxWire alloy minimizes outward dentinal stress(\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e). Collectively, these findings confirm that all three systems can safely retrieve fractured instruments without compromising root strength.\u003c/p\u003e \u003cp\u003eA marked difference emerged in retrieval success: LeoPen (88.9%)\u0026thinsp;\u0026gt;\u0026thinsp;Ultrasonic (66.7%)\u0026thinsp;\u0026gt;\u0026thinsp;XP-Endo Shaper (11.1%). LeoPen\u0026rsquo;s flexible nitinol loop achieved secure engagement with minimal dentin loss, consistent with prior results for similar loop systems(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e). Ultrasonics performed moderately well but carried a risk of perforation, corroborating Portela et al. (2022)(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). The XP-Endo Shaper\u0026rsquo;s poor success was mainly due to instrument re-fracture, a problem previously noted in curved canals(\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e). Although the XP-Endo Shaper achieved the shortest mean retrieval time, this was clinically meaningless given its high failure rate. Conversely, LeoPen required slightly more time but produced the most predictable and safe results(\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e). The absence of correlation between retrieval time and VFR (r = \u0026minus;\u0026thinsp;0.13, p\u0026thinsp;\u0026gt;\u0026thinsp;0.05) further confirms that longer procedures do not inherently weaken roots when performed carefully.\u003c/p\u003e \u003cp\u003eIn our study, most samples exhibited vertical fractures, consistent across groups, with no significant intergroup differences. This pattern mirrors the typical stress distribution observed in endodontically treated molars under axial loading(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e). The lack of difference among systems implies that the retrieval technique affects the success rate more than the fracture mode.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWithin the limitations of this in-vitro study, all three retrieval systems\u0026mdash;Ultrasonic tip, XP-Endo Shaper, and LeoPen loop\u0026mdash;demonstrated comparable vertical fracture resistance of mandibular molar roots, indicating that none of the techniques significantly weakened the tooth structure.\u003c/p\u003e \u003cp\u003eHowever, apparent differences were observed in retrieval success rates, with the LeoPen loop achieving the highest, followed by Ultrasonic, and XP-Endo Shaper showing the lowest.\u003c/p\u003e \u003cp\u003eAlthough the XP-Endo Shaper provided shorter retrieval times, this efficiency was offset by frequent re-fracture and procedural failure. Accordingly, the null hypothesis was accepted for fracture resistance but rejected for retrieval success, confirming that the choice of technique strongly affects clinical outcome while maintaining root integrity.\u003c/p\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eClinical Significance\u003c/h2\u003e \u003cp\u003eSuccessful removal of separated instruments must balance efficiency, safety, and dentin preservation. This study demonstrates that loop-based retrieval systems, such as LeoPen, offer a predictable, conservative, and structurally safe approach for managing fractured instruments in curved molar canals. Ultrasonic retrieval remains effective for accessible fragments but carries a moderate risk of perforation. In contrast, XP-Endo Shaper is not recommended as a standalone retrieval method due to its high failure tendency. Clinicians should therefore prioritize controlled, magnified retrieval over speed to ensure long-term tooth survival.\u003c/p\u003e \u003c/div\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eDOM: dental operating microscope\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEDTA: Ethylenediaminetetraacetic acid\u003c/p\u003e\n\u003cp\u003eMin: minute\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eN: newton\u003c/p\u003e\n\u003cp\u003eNaOCl: sodium hypochlorite\u003c/p\u003e\n\u003cp\u003eREC: Research Ethical Committee\u003c/p\u003e\n\u003cp\u003eSD: standard deviation\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eVFR: vertical fracture resistance\u003c/p\u003e\n\u003cp\u003eVRF: vertical root fracture\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eEthics Approval and Consent to Participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was conducted in full alignment with the principles of the Declaration of Helsinki. Ethical approval was obtained from the Research Ethics Committee, Faculty of Dentistry, Cairo University, under approval number 26-6-2023. As this was an in vitro study that did not involve human participants, the Committee deemed informed consent unnecessary.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for Publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during the current study are available from the corresponding author on reasonable request. All experimental data, measurement tables, and statistical analysis files supporting the conclusions of this article are stored at the Faculty of Dentistry, Cairo University, and can be provided in anonymized form upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author declares that there are no competing\u0026nbsp;interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit\u0026nbsp;sectors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor’s Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eM.A. conceived and designed the study, performed the experiments, analyzed the data, and wrote the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eN.N. research planning, designing, research execution, and data monitoring. Contributed statistical analysis of the results, wrote the research report, and the article to be published.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eN.H. Sequence generation, allocation concealment, randomization, data management, and proofreading the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eTerauchi Y, O\u0026apos;Leary L, Suda H. Removal of separated files from root canals with a new file-removal system: Case reports. Journal of endodontics. 2006;32(8):789-97.\u003c/li\u003e\n\u003cli\u003eShahabinejad H, Ghassemi A, Pishbin L, Shahravan A. Success of ultrasonic technique in removing fractured rotary nickel-titanium endodontic instruments from root canals and its effect on the required force for root fracture. Journal of endodontics. 2013;39(6):824-8.\u003c/li\u003e\n\u003cli\u003eFu M, Huang X, Zhang K, Hou B. Effects of Ultrasonic Removal of Fractured Files from the Middle Third of Root Canals on the Resistance to Vertical Root Fracture. Journal of endodontics. 2019;45(11):1365-70.\u003c/li\u003e\n\u003cli\u003eDulundu M, Helvacioglu-Yigit D. The Efficiency of the BTR-Pen System in Removing Different Types of Broken Instruments from Root Canals and Its Effect on the Fracture Resistance of Roots. Materials (Basel, Switzerland). 2022;15(17).\u003c/li\u003e\n\u003cli\u003eAbdeen MA, Plotino G, Hassanien EE, Turky M. Evaluation of Dentine Structure Loss after Separated File Retrieval by Three Different Techniques: An Ex-vivo Study. European endodontic journal. 2023;8(3):225-30.\u003c/li\u003e\n\u003cli\u003ePruthi PJ, Nawal RR, Talwar S, Verma M. Comparative evaluation of the effectiveness of ultrasonic tips versus the Terauchi file retrieval kit for the removal of separated endodontic instruments. Restorative dentistry \u0026amp; endodontics. 2020;45(2):e14.\u003c/li\u003e\n\u003cli\u003eLobo WMV, Sayed A, Sapkale K, Ramugade M, Benavides ACM. A comparative evaluation of the resistance to vertical root fracture after removal of separated instruments using three instrument retrieval systems: An in vitro study. Journal of conservative dentistry and endodontics. 2025;28(2):182-6.\u003c/li\u003e\n\u003cli\u003eMahale VD, Saxena T, Sharma S, Mohan EA. Quantitative analysis of troughing depth for successful instrument retrieval using the loop technique: A cross-sectional in vivo study. Journal of conservative dentistry and endodontics. 2025;28(4):360-5.\u003c/li\u003e\n\u003cli\u003eShajahan S, Dhanavel C, Raja SV, Sornamalar M, Balavaishnavi G. Comparative Evaluation of the Efficiency in Retrieving Separated Reciprocating Instruments Using Three Different File Retrieval Systems in Maxillary First Molars: An In Vitro Study. Journal of pharmacy \u0026amp; bioallied sciences. 2024;16(Suppl 5):S4544-s7.\u003c/li\u003e\n\u003cli\u003eEskibağlar M, \u0026Ouml;zata MY, Ocak MS, \u0026Ouml;ztekin F. Investigation of fracture prevalence of instruments used in root canal treatments at a faculty of dentistry: a prospective study. Restorative dentistry \u0026amp; endodontics. 2023;48(4):e38.\u003c/li\u003e\n\u003cli\u003eGarrocho A, S\u0026aacute;nchez-Reynoso A, Berber MA, Ruiz-Rodr\u0026iacute;guez M, Pozos-Guill\u0026eacute;n A. Clinical Management of Intra-Pulp Canal Broken Endodontic Files in Primary Teeth: Literature Review. Odovtos - International Journal of Dental Sciences. 2020;23:16-20.\u003c/li\u003e\n\u003cli\u003eBarakat F, Attia M. Effect of Two Techniques of Separated File Removal Systems on Dentin Loss and Fracture Resistance of Teeth (In Vitro Study). Egyptian Dental Journal. 2024;70:2877-84.\u003c/li\u003e\n\u003cli\u003eSilva E, Lima CO, Barbosa AFA, Augusto CM, Souza EM, Lopes RT, et al. Preserving dentine in minimally invasive access cavities does not strength fracture resistance of restored mandibular molars. International endodontic journal. 2021;54(6):966-74.\u003c/li\u003e\n\u003cli\u003eMadarati AA, Qualtrough AJ, Watts DC. Vertical fracture resistance of roots after ultrasonic removal of fractured instruments. International endodontic journal. 2010;43(5):424-9.\u003c/li\u003e\n\u003cli\u003eYassa S, Nabeel M, Ghobashy A, Alkhawas M. Fracture resistance and volumetric dentin change after management of broken instrument using static navigation \u0026ndash; An in vitro study. Journal of conservative dentistry and endodontics. 2025;28:319-24.\u003c/li\u003e\n\u003cli\u003eUslu G, \u0026Ouml;zy\u0026uuml;rek T, Yılmaz K, G\u0026uuml;ndoğar M, Plotino G. Apically Extruded Debris during Root Canal Instrumentation with Reciproc Blue, HyFlex EDM, and XP-endo Shaper Nickel-titanium Files. Journal of endodontics. 2018;44(5):856-9.\u003c/li\u003e\n\u003cli\u003eJitesh S, Surendran S, Natanasabapathy V. Efficacy of two instrument retrieval techniques in removing separated rotary and reciprocating nickel-titanium files in mandibular molars - An in vitro study. Journal of conservative dentistry and endodontics. 2024;27(12):1240-5.\u003c/li\u003e\n\u003cli\u003ePortela NN, Rech JP, Marchionatti AME, Barasuol JC. Techniques to address fractured instruments in the middle or apical third of the root canal in human permanent teeth: a systematic review of the in vitro studies. Clinical oral investigations. 2022;26(1):131-9.\u003c/li\u003e\n\u003cli\u003eJamleh A, Albanyan H, Alaqla A, Alissa H, Alshetan N, Alraffa S, et al. Impact of cooling on shaping ability of thermally treated files in canal models with double curvature. PeerJ. 2023;11:e15830.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"instrument separation, instrument retrieval, ultrasonics, wire and loop, time","lastPublishedDoi":"10.21203/rs.3.rs-8090679/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8090679/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eSeparated endodontic instruments are a frequent procedural challenge that can compromise treatment outcomes. Retrieval techniques vary in efficiency and may influence root integrity. This study compared the impact of three retrieval systems\u0026mdash;ultrasonic tips, LeoPen loop, and XP-Endo Shaper\u0026mdash;on vertical fracture resistance (VFR), retrieval time, and retrieval success.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTwenty-seven extracted human mandibular molars with moderately curved mesial roots (15\u0026ndash;30\u0026deg;) were randomly allocated into three groups (n\u0026thinsp;=\u0026thinsp;9): Ultrasonic Tip (Ed4), XP-Endo Shaper, and LeoPen Loop. A 4 mm NiTi fragment was fractured in the middle third of each canal. Retrieval was performed under magnification, and success (yes/no), retrieval time (min), and post-retrieval VFR (N) were measured using a universal testing machine. Data were analyzed using one-way ANOVA and Fisher\u0026rsquo;s exact test (α\u0026thinsp;=\u0026thinsp;0.05).\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe LeoPen Loop system achieved the highest retrieval success (88.9%), followed by ultrasonics (66.7%), while the XP-Endo Shaper had the lowest (11.1%) (FEp\u0026thinsp;=\u0026thinsp;0.001). Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD retrieval times were 25.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.8 min, 24.0\u0026thinsp;\u0026plusmn;\u0026thinsp;7.7 min, and 19.8\u0026thinsp;\u0026plusmn;\u0026thinsp;5.6 min, respectively (p\u0026thinsp;=\u0026thinsp;0.11). Mean\u0026thinsp;\u0026plusmn;\u0026thinsp;SD VFR values were 711.8\u0026thinsp;\u0026plusmn;\u0026thinsp;230.1 N (ultrasonic), 730.4\u0026thinsp;\u0026plusmn;\u0026thinsp;241.0 N (XP-Endo Shaper file), and 710.0\u0026thinsp;\u0026plusmn;\u0026thinsp;215.3 N (LeoPen), showing no significant differences (p\u0026thinsp;=\u0026thinsp;0.95). A weak, non-significant correlation existed between retrieval time and VFR (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.13, p\u0026thinsp;=\u0026thinsp;0.53).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eAll three systems preserved comparable vertical fracture resistance. The LeoPen Loop achieved the highest retrieval success with minimal complications, making it a reliable and conservative technique for removing separated instruments from moderately curved canals. Ultrasonic retrieval remains effective when applied carefully, whereas the XP-Endo Shaper demonstrated limited success in this context.\u003c/p\u003e","manuscriptTitle":"Comparative Evaluation of Vertical Fracture Resistance and Retrieval Outcomes Using Ultrasonic, LeoPen Loop, and XP-Endo Shaper Systems: An In Vitro Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-29 18:57:43","doi":"10.21203/rs.3.rs-8090679/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-27T11:37:42+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-06T05:27:31+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-01T07:11:37+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-12-30T19:50:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"66412669890216584653650158805816476627","date":"2025-12-28T11:03:55+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"1257062065440841611372337435321815033","date":"2025-12-28T06:31:03+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"150908068592436771739492570959764455627","date":"2025-12-27T12:59:52+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"136196688452892157375894851895548118739","date":"2025-12-26T14:30:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-12-26T06:29:32+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-03T06:58:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-03T04:45:46+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-01T13:13:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Oral Health","date":"2025-12-01T11:49:02+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-oral-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"ohea","sideBox":"Learn more about [BMC Oral Health](http://bmcoralhealth.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/ohea/default.aspx","title":"BMC Oral Health","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"5fcc170f-bdf1-47d4-b1dc-be9ff3dd556a","owner":[],"postedDate":"December 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-03-25T09:24:28+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-29 18:57:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8090679","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8090679","identity":"rs-8090679","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}