title: Deformations and cyclic fatigue resistance of nickel-titanium instruments inside a sequence.
abstract: OBJECTIVE
  To compare the effect of brushing motion on torsional and cyclic fatigue resistance of TF Adaptive instruments after clinical use.
  
  
  METHODS
  20 packs of TFA small sequence (SybronEndo, Orange, CA, USA) were used for this study and divided into two groups. Each instrument prepared one resin tooth, consisting in 4 canals with a complex anatomy. In group A, no brushing motion was performed. In group B, after the green instrument reached the working length, brushing motion with circumferential filing was performed for 15 seconds in each canal (overall 1 minute). All the instruments were then subjected to cyclic fatigue test and mean values and standard deviation for time to fracture were evaluated. Data were subjected to one-way analysis of variance and Bonferroni t-test procedure with a significance set at P < 0.05.
  
  
  RESULTS
  No instruments were broken during preparation of root canals. Two TF Adaptive green and 5 yellow showed unwinding after intracanal clinical use. No statistically significant differences were found between green instruments of both groups (P > 0.05), while a statistically significant difference was found between the yellow instruments (P < 0.05), with group B showing an higher resistance to cyclic fatigue.
  
  
  CONCLUSIONS
  A prolonged passive brushing motion did not adversely affected mechanical resistance of the instrument used for this purpose. Resistance to both deformations and cyclic fatigue of the second instrument within the TFA small sequence was enhanced by the coronal flaring provided by the brushing action of the first instrument used.
authors.affiliation: Endodontics Unit, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Gambarini
authors.affiliation: Endodontics Unit, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Plotino
authors.affiliation: PUC University, Curitiba, Brasil.
authors.forename: Lucila
authors.initials: L
authors.lastname: Piasecki
authors.affiliation: Department of Restorative Dental Science, College of Dentistry, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Dina
authors.initials: D
authors.lastname: Al-Sudani
authors.affiliation: Endodontics Unit, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Testarelli
authors.affiliation: University of Rome II, Tor Vergata, Italy.
authors.forename: Gianpaolo
authors.initials: G
authors.lastname: Sannino
keywords: brushing action; cyclic fatigue; deformations; nickel-titanium