title: Cyclic fatigue resistance of nickel-titanium instruments after immersion in irrigant solutions with or without surfactants.
abstract: BACKGROUND
  The aim of the study was to assess cyclic fatigue resistance of reciprocating (Reciproc and WaveOne) and continuous rotating (ProTaper) nickel-titanium files after immersion in different irrigation solutions with or without surfactants during several short time periods.
  
  
  METHODS
  A total of 270 new Reciproc R25, WaveOne Primary, and ProTaper F2 files were tested. Instruments of each brand were divided into 1 control group (n = 10) formed by new files and 4 test groups (n = 20) formed by instruments dynamically immersed at 37°C for 16 mm in 5.25% sodium hypochlorite (NaOCl), Hypoclean (5.25% NaOCl with surfactant), 17% EDTA, or EDTA Plus (17% EDTA with surfactant). Each test group was subdivided into 2 subgroups (n = 10) on the basis of the time of dynamic immersion in the endodontic irrigant solution (45 seconds or 3 minutes). Resistance to cyclic fatigue was determined by recording time to fracture in a stainless steel artificial canal with a 60° angle of curvature and 5-mm radius of curvature. The fracture surface was examined by using scanning electron microscopy.
  
  
  RESULTS
  Immersion in NaOCl did not reduce the cyclic fatigue of reciprocating or continuous nickel-titanium files. The 17% EDTA reduced the fatigue resistance of all instruments after 3 minutes. The immersion in irrigants with surfactants did not influence the cyclic fatigue of instruments except for Reciproc immersed in Hypoclean solution.
  
  
  CONCLUSIONS
  EDTA immersion reduced the cyclic fatigue resistance of all instruments after 3 minutes. Addition of surfactants did not influence the cyclic fatigue of files except when added to NaOCl when it contacts Reciproc instruments.
authors: Department of Surgery, University of Catania, Catania, Italy. Electronic address: eugeniopedulla@gmail.com.
authors: Eugenio
authors: E
authors: Pedullà
authors: Department of Dental Sciences, Tuscan School of Dental Medicine, University of Siena, Siena, Italy.
authors: Giovanni
authors: G
authors: Franciosi
authors: Department of Dental Sciences, Tuscan School of Dental Medicine, University of Siena, Siena, Italy.
authors: Hani F
authors: HF
authors: Ounsi
authors: Department of Dental Sciences, Tuscan School of Dental Medicine, University of Siena, Siena, Italy.
authors: Marella
authors: M
authors: Tricarico
authors: Department of Surgery, University of Catania, Catania, Italy.
authors: Ernesto
authors: E
authors: Rapisarda
authors: Department of Dental Sciences, Tuscan School of Dental Medicine, University of Siena, Siena, Italy.
authors: Simone
authors: S
authors: Grandini
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D004492:Edetic Acid / Q000737:chemistry; D004868:Equipment Failure; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D011897:Random Allocation; D012388:Root Canal Irrigants / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D012973:Sodium Hypochlorite / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D012388:Root Canal Irrigants; D013501:Surface-Active Agents; C040654:titanium nickelide; D009532:Nickel; D004492:Edetic Acid; D014025:Titanium; D012973:Sodium Hypochlorite
keywords: Cyclic fatigue; EDTA; nickel-titanium; reciprocating instruments; sodium hypochlorite; surfactant