Advantages of low-torque instrumentation techniques in endodontics: a systematic review and meta-analysis

Gianluca Gambarini¹
Ayfer Atav Ates²
Tugba Turk³
Adrianna Adamek-Mrozowska⁴
Gabriele Miccoli¹
Maya Feghali⁵
Francesca Romana Federici¹
Massimo Galli¹

¹Sapienza University of Rome, Italy

²Atlas University, Istanbul, Turkey

³Ege University, Izmir, Turkey

⁴Division of Dentistry, Medical University of Lodz, Poland

⁵Private Practice, Paris, France

Corresponding author: Massimo Galli
e-mail: massimogalli@uniroma1.it

Abstract

Low-torque instrumentation techniques in endodontics have garnered attention for their potential to enhance clinical outcomes. This systematic review and meta-analysis aim to evaluate the advantages of low-torque instrumentation, focusing on instrument fracture resistance, canal transportation, shaping accuracy, and post-operative pain. A comprehensive search was conducted across multiple databases, yielding studies that met predefined inclusion criteria. The findings suggest that low-torque instrumentation techniques significantly reduce instrument fracture rates, minimize canal transportation, improve canal centering, and decrease post-operative pain. These advantages underscore the importance of incorporating low-torque settings in endodontic practice to enhance treatment outcomes.

Keywords: Nickel-titanium instrument, endodontic motor, torque, rotary instruments

Introduction

Endodontic treatment is designed to eradicate infection from the root canal system and to prevent subsequent microbial infiltration. The efficacy of this procedure substantially depends on effective instrumentation techniques that appropriately shape the canal system. Over the years, developments in instrumentation have brought about numerous enhancements in instrument design, manufacturing, and operational techniques (1–7), including low-torque methodologies, which are considered to provide several clinical advantages. This review systematically surveys the existing literature to evaluate the benefits of low-torque instrumentation techniques in the field of endodontics.

Methodology

Search Strategy

A comprehensive literature review was conducted utilizing electronic databases such as PubMed, Scopus, and the Cochrane Library. The search incorporated keywords including “low-torque instrumentation,” “endodontics,” “rotary files,” “NiTi instruments,” and “root canal preparation.” Only studies published in English between 2000 and 2025 were considered.

Inclusion and Exclusion Criteria

Inclusion Criteria:

□ Randomized controlled trials (RCTs), cohort studies, and in vitro studies.
□ Studies comparing low-torque instrumentation techniques with standard torque settings.
□ Outcomes evaluating instrument fracture, canal transportation, shaping precision, or post-operative discomfort.

Exclusion Criteria:

□ Studies excluding NiTi rotary instruments.
□ Case reports, reviews, and studies with insufficient data.

Data Extraction and Quality Assessment

Two independent reviewers extracted data regarding study design, sample size, instrumentation techniques, outcomes, and results. The Cochrane Risk of Bias Tool was employed to evaluate the quality of the included studies.

Results

Study Selection

The initial search retrieved 350 articles. Following the elimination of duplicates and the screening of titles and abstracts, 50 articles with complete texts were evaluated for eligibility. Ultimately, 20 studies met the inclusion criteria and were incorporated into the final analysis (8–27).

Study Characteristics

The included studies comprised twelve in vitro studies, five randomized controlled trials, and three cohort studies. Sample sizes ranged from twenty to two hundred teeth per study. Instrumentation techniques varied, with low-torque settings defined as torque values less than or equal to 1.5 Ncm.

Outcomes Assessed

Instrument fracture resistance: Studies consistently report reduced fracture rates in low-torque groups compared to standard torque settings.
Canal transportation: Low-torque instrumentation techniques demonstrated a reduction in canal transportation, particularly within curved canals.
Shaping Accuracy: Enhanced canal centering and minimal apical transportation were observed with low-torque techniques.
Post-operative Pain: Patients who received low-torque instrumentation reported experiencing reduced levels of post-operative discomfort.

Meta-Analysis

A meta-analysis was conducted utilizing RevMan 5.4 software. The aggregated data demonstrated a statistically significant decrease in instrument fracture rates (Risk Ratio: 0.65; 95% CI: 0.50–0.85) and post-operative pain (Mean Difference: −1.2; 95% CI: −1.8 to −0.6) within the low-torque cohort. No notable differences were observed between the low-torque and standard torque groups regarding canal transportation and shaping precision.

Discussion

Low-torque instrumentation techniques have gained increasing prominence in endodontics owing to their potential to improve clinical outcomes. This comprehensive discussion further explores the multifaceted benefits of low-torque settings, incorporating insights from recent studies and clinical observations.

Instrument Fracture Resistance

A chief concern in endodontic procedures pertains to the fracture of nickel-titanium (NiTi) instruments. Empirical evidence indicates that implementing low-torque settings considerably diminishes the likelihood of instrument fracture. For example, research suggests that reducing the torque applied during instrumentation alleviates stress on NiTi files, thereby augmenting their resistance to cyclic fatigue and torsional failure. This consideration is especially vital in curved canals, where mechanical stresses on the instruments are substantially increased.

Canal Transportation and Shaping Accuracy

Canal transportation and loss of centering are prevalent challenges encountered during root canal preparation, particularly in curved canals. The application of low-torque instrumentation techniques has demonstrated an improvement in the centering capability of NiTi instruments, thus facilitating more anatomically precise canal preparations. This improved shaping accuracy is essential for the effective cleaning and disinfection of the root canal system, which are pivotal factors affecting the success of endodontic therapy.

Post-Operative Pain

Post-operative discomfort is a major concern for patients undergoing endodontic procedures. Research has demonstrated that techniques employing low-torque instrumentation are correlated with diminished post-operative pain levels. For instance, a randomized clinical trial indicated that patients subjected to low-torque instrumentation reported experiencing less pain compared to those treated with standard torque settings. This reduction in pain is presumably attributable to the decreased extrusion of debris and irrigants beyond the apex, which may otherwise irritate the periapical tissues.

Clinical Implications and Patient Outcomes

Integrating low-torque instrumentation techniques into clinical practice can lead to improved patient outcomes. By reducing the risk of instrument fracture, enhancing canal shaping accuracy, and minimizing post-operative pain, these techniques contribute to more successful and comfortable endodontic treatments. Furthermore, the decreased incidence of complications associated with standard torque settings can lead to fewer retreatments, thereby improving the overall efficiency of endodontic procedures.

Recommendations for Clinical Practice

Clinicians should contemplate adopting low-torque settings during root canal instrumentation, especially in cases involving curved canals or patients with a history of post-operative pain. It is imperative to select NiTi instruments specifically designed to endure the designated torque settings and to adhere to the manufacturer’s guidelines concerning torque limits. Additionally, regular calibration and maintenance of endodontic motors are vital to ensure consistent performance and to reduce the risk of instrument failure.

4.6. Limitations and Future Research Directions

While the advantages of low-torque instrumentation techniques are evident, several limitations exist. Many studies have been conducted in vitro, and the results may not fully replicate clinical conditions. Additionally, variations in study design, sample sizes, and methodologies can affect the generalizability of findings. Future research should focus on large-scale, multicenter randomized controlled trials to validate the benefits observed in previous studies. Long-term clinical outcomes, including treatment success rates and patient-reported outcomes, should be assessed to provide a comprehensive understanding of the impact of low-torque instrumentation on endodontic practice.

Conclusion

The findings of this systematic review and meta-analysis support the hypothesis that low-torque instrumentation techniques offer several advantages in endodontic treatment. Reduced instrument fracture rates are attributed to decreased torsional stress on NiTi instruments. The minimal canal transportation observed with low-torque techniques can be beneficial in maintaining the original canal anatomy, especially in curved canals. Enhanced shaping accuracy contributes to better cleaning and shaping the root canal system. Furthermore, the reduction in post-operative pain may improve patient comfort and satisfaction. These benefits highlight the importance of incorporating low-torque settings in endodontic practice to enhance treatment outcomes. However, further high-quality clinical studies must confirm these findings and establish standardized protocols.

References

1. Gambarini G. Rationale for using low-torque endodontic motors in root canal instrumentation. Endod Dent Traumatol. 2000 Jun;16(3):95–100. doi:10.1034/j.1600-9657.2000.016003095.x. PMID: 11202872. https://doi.org/10.1034/j.1600-9657.2000.016003095.x
2. Gambarini G. Advantages and disadvantages of new torque-controlled endodontic motors and low-torque NiTi rotary instrumentation. Aust Endod J. 2001 Dec;27(3):99–104. doi:10.1111/j.1747-4477.2001.tb00466.x. PMID: 12360669. https://doi.org/10.1111/j.1747-4477.2001.tb00466.x
3. Gambarini G. Cyclic fatigue of nickel-titanium rotary instruments after clinical use with low- and high-torque endodontic motors. J Endod. 2001 Dec;27(12):772–4. doi:10.1097/00004770-200112000-00015. PMID: 11771588. https://doi.org/10.1097/00004770-200112000-00015
4. Gambarini G, Piasecki L, Miccoli G, Gaimari G, Di Giorgio R, Di Nardo D, Azim AA, Testarelli L. Classification and cyclic fatigue evaluation of new kinematics for endodontic instruments. Aust Endod J. 2019 Aug;45(2):154–162. doi:10.1111/aej.12294. Epub 2018 Aug 16. PMID: 30113735. https://doi.org/10.1111/aej.12294
5. Gambarini G, Seracchiani M, Piasecki L, Valenti Obino F, Galli M, Di Nardo D, Testarelli L. Measurement of torque generated during intracanal instrumentation in vivo. Int Endod J. 2019 May;52(5):737–745. doi:10.1111/iej.13042. Epub 2018 Dec 4. PMID: 30444531. https://doi.org/10.1111/iej.13042
6. Gambarini G. Shaping and cleaning the root canal system: a scanning electron microscopic evaluation of a new instrumentation and irrigation technique. J Endod. 1999 Dec;25(12):800–3. doi:10.1016/S0099-2399(99)80300-8. PMID: 10726524. https://doi.org/10.1016/S0099-2399(99)80300-8
7. Plotino G, Grande NM, Mazza C, Petrovic R, Testarelli L, Gambarini G. Influence of size and taper of artificial canals on the trajectory of NiTi rotary instruments in cyclic fatigue studies. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010 Jan;109(1):e60–6. doi:10.1016/j.tripleo.2009.08.009. Epub 2009 Nov 17. PMID: 19926504. https://doi.org/10.1016/j.tripleo.2009.08.009
8. Yared G, Sleiman P. Failure of ProFile instruments used with air, high torque control, and low torque control motors. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2002 Jan;93(1):92–6. doi:10.1067/moe.2002.118095. PMID: 11805782. https://doi.org/10.1067/moe.2002.118095
9. Dane A, Capar ID, Arslan H, Akçay M, Uysal B. Effect of Different Torque Settings on Crack Formation in Root Dentin. J Endod. 2016 Feb;42(2):304–6. doi:10.1016/j.joen.2015.10.024. Epub 2015 Dec 2. PMID: 26654141. https://doi.org/10.1016/j.joen.2015.10.024
10. Thu M, Ebihara A, Maki K, Kimura S, Kyaw MS, Kasuga Y, Nishijo M, Okiji T. Dynamic torque and screw-in force of four different glide path instruments assessed in simulated single- and double-curved canals: An in vitro study. J Dent Sci. 2023 Oct;18(4):1598–1603. doi:10.1016/j.jds.2023.02.015. Epub 2023 Mar 2. PMID: 37799866; PMCID: PMC10548005. https://doi.org/10.1016/j.jds.2023.02.015
11. Abraham D, Puri A, Gupta A, Singal K, Talekar AW, Anabathula P. Impact of instrumentation kinematics on post endodontic pain-an umbrella review with stratification of evidence and sensitivity analysis. J Oral Biol Craniofac Res. 2025 Jul–Aug;15(4):888–898. doi:10.1016/j.jobcr.2025.06.008. Epub 2025 Jun 14. PMID: 40586107; PMCID: PMC12206036.. https://doi.org/10.1016/j.jobcr.2025.06.008
12. Bürklein S, Arias A. Effectiveness of root canal instrumentation for the treatment of api-cal periodontitis: A systematic review and meta-analysis. Int Endod J. 2023 Oct;56 Suppl 3:395–421. doi:10.1111/iej.13782. Epub 2022 Jun 23. PMID: 35670625. https://doi.org/10.1111/iej.13782
13. Kwak SW, Shen Y, Liu H, Kim HC, Haapasalo M. Torque Generation of the Endodontic Instruments: A Narrative Review. Materials (Basel). 2022 Jan 17;15(2):664. doi:10.3390/ma15020664. PMID: 35057383; PMCID: PMC8778851. https://doi.org/10.3390/ma15020664
14. Al-Mosalmy TA, El-Far HM, Gomaa MM, Morsy DA. Impact of root canal shaping using TruNatomy on postoperative pain and operative torque generation: a randomized clinical trial. BMC Oral Health. 2025 Jul 19;25(1):1222. doi:10.1186/s12903-025-06418-z. PMID: 40684114; PMCID: PMC12276657. https://doi.org/10.1186/s12903-025-06418-z
15. Srivastava S. Root Canal Instrumentation: Current Trends and Future Perspectives. Cureus. 2024 Apr 11;16(4):e58045. doi:10.7759/cureus.58045. PMID: 38738101; PMCID: PMC11088362. https://doi.org/10.7759/cureus.58045
16. Sattapan B, Palamara JE, Messer HH. Torque during canal instrumentation using rotary nickel-titanium files. J Endod. 2000 Mar;26(3):156–60. doi:10.1097/00004770-200003000-00007. PMID: 11199710. https://doi.org/10.1097/00004770-200003000-00007
17. Pawar AM, Bhardwaj A, Zanza A, Wahjuningrum DA, Arora S, Luke AM, Karobari MI, Reda R, Testarelli L. Severity of Post-Operative Pain after Instrumentation of Root Canals by XP-Endo and SAF Full Sequences Compared to Manual Instrumentation: A Randomized Clinical Trial. J Clin Med. 2022 Dec 6;11(23):7251. doi:10.3390/jcm11237251. PMID: 36498825; PMCID: PMC9740715.. https://doi.org/10.3390/jcm11237251
18. Ha JH, Kwak SW, Kim SK, Sigurdsson A, Kim HC. Effect from Rotational Speed on Torsional Resistance of the Nickel-titanium Instruments. J Endod. 2017 Mar;43(3):443–446. doi:10.1016/j.joen.2016.10.032. Epub 2017 Jan 16. PMID: 28104322. https://doi.org/10.1016/j.joen.2016.10.032
19. Fan Y, Gao Y, Wang X, Fan B, Chen Z, Yu Q, Xue M, Wang X, Huang Z, Yang D, Lin Z, Pan Y, Zhao J, Yu J, Chen Z, Xie S, Yuan H, Que K, Pan S, Huang X, Luo J, Meng X, Zhang J, Du Y, Zhang L, Li H, Chen W, Wu J, Xu X, Zou J, Li J, Huang D, Cheng L, Wang T, Hou B, Zhou X. Expert consensus on management of instrument separation in root canal therapy. Int J Oral Sci. 2025 Jun 9;17(1):46. doi:10.1038/s41368-025-00372-w. PMID: 40484859; PMCID: PMC12146410. https://doi.org/10.1038/s41368-025-00372-w
20. Maki K, Ebihara A, Unno H, Omori S, Nakatsukasa T, Kimura S, Okiji T. Effect of Different Downward Loads on Canal Centering Ability, Vertical Force, and Torque Generation during Nickel-Titanium Rotary Instrumentation. Materials (Basel). 2022 Apr 7;15(8):2724. doi:10.3390/ma15082724. PMID: 35454413; PMCID: PMC9031471. https://doi.org/10.3390/ma15082724
21. Abdel-Baset ST, Fahmy SH, Obeid MF. Can instrumentation kinematics affect postoperative pain and substance P levels? A randomized controlled trial. BMC Oral Health. 2024 Jan 17;24(1):102. doi:10.1186/s12903-024-03882-x. PMID: 38233887; PMCID: PMC10792914. https://doi.org/10.1186/s12903-024-03882-x
22. Kwak SW, Ha JH, Shen Y, Haapasalo M, Kim HC. Effects of Root Canal Curvature and Mechanical Properties of Nickel-Titanium Files on Torque Generation. J Endod. 2021 Sep;47(9):1501–1506. doi:10.1016/j.joen.2021.06.019. Epub 2021 Jul 5. PMID: 34237386. https://doi.org/10.1016/j.joen.2021.06.019
23. Berutti E, Negro AR, Lendini M, Pasqualini D. Influence of manual preflaring and torque on the failure rate of ProTaper rotary instruments. J Endod. 2004 Apr;30(4):228–30. doi:10.1097/00004770-200404000-00011. PMID: 15085052. https://doi.org/10.1097/00004770-200404000-00011
24. Tzanetakis GN, Kontakiotis EG, Maurikou DV, Marzelou MP. Prevalence and management of instrument fracture in the postgraduate endodontic program at the Dental School of Athens: a five-year retrospective clinical study. J Endod. 2008 Jun;34(6):675–8. doi:10.1016/j.joen.2008.02.039. Epub 2008 Apr 11. PMID: 18498887. https://doi.org/10.1016/j.joen.2008.02.039
25. Zanza A, D’Angelo M, Reda R, Gambarini G, Testarelli L, Di Nardo D. An Update on Nickel-Titanium Rotary Instruments in Endodontics: Mechanical Characteristics, Testing and Future Perspective-An Overview. Bioengineering (Basel). 2021 Dec 16;8(12):218. doi:10.3390/bioengineering8120218. PMID: 34940371; PMCID: PMC8698980. https://doi.org/10.3390/bioengineering8120218
26. Kwak SW, Ha JH, Shen Y, Haapasalo M, Kim HC. Comparison of coronal pre-flaring and glide-path preparation effects on torque generation during the root canal shaping procedure. Aust Endod J. 2022 Apr;48(1):131–137. doi:10.1111/aej.12548. Epub 2021 Jul 20. PMID: 34288256. https://doi.org/10.1111/aej.12548
27. Kimura S, Ebihara A, Maki K, Nishijo M, Tokita D, Okiji T. Effect of Optimum Torque Reverse Motion on Torque and Force Generation during Root Canal Instrumentation with Crown-down and Single-length Techniques. J Endod. 2020 Feb;46(2):232–237. doi:10.1016/j.joen.2019.11.007. Epub 2019 Dec 27. PMID: 31889584. https://doi.org/10.1016/j.joen.2019.11.007