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J Oral Maxillofac Res. 2016 Dec 28;7(4):e5. doi: 10.5037/jomr.2016.7405. eCollection 2016 Oct-Dec.

Incidence of Deformation and Fracture of Twisted File Adaptive Instruments after Repeated Clinical Use.

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Department of Oral and Maxillo Facial Sciences, Sapienza University of Rome, Rome Italy.
Department of Periodontics and Endodontics, University at Buffalo School of Dental Medicine, Buffalo, New York USA.
Department of Endodontics, Pontifical Catholic University of ParanĂ , Curitiba, ParanĂ¡ Brazil.
Department of Restorative Dental Sciences, College of Dentistry, King Saud University, Riyadh Saudi Arabia.



The aim of the present study was to investigate the incidence of deformation and fracture of twisted file adaptive nickel-titanium instruments after repeated clinical use and to identify and check whether the three instruments within the small/medium sequence showed similar or different visible signs of metal fatigue.


One-hundred twenty twisted file adaptive (TFA) packs were collected after clinically used to prepare three molars and were inspected for deformations and fracture.


The overall incidence of deformation was 22.2%, which was not evenly distributed within the instruments: 15% for small/medium (SM)1 (n = 18), 38.33% for SM2 (n = 46) and 13.33% for the SM3 instruments (n = 16). The defect rate of SM2 instruments was statistically higher than the other two (P < 0.001). The fracture rate was 0.83% (n = 3), being two SM2 instruments and one SM3.


It was observed a very low defect rate after clinical use of twisted file adaptive rotary instruments. The untwisting of flutes was significantly more frequent than fracture, which might act as prevention for breakage. The results highlight the fact that clinicians should be aware that instruments within a sequence might be differently subjected to intracanal stress.


endodontics; nickel; root canal therapy; titanium

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