title: Cyclic fatigue resistance of new and used Mtwo rotary nickel-titanium instruments in two different radii of curvature.
abstract: The fracture of nickel-titanium rotary instruments is a serious problem that can jeopardise the outcome of root canal treatment. The aim of this study was to compare the cyclic fatigue resistance of new and used Mtwo rotary nickel-titanium instruments in artificial canals with two different radii of curvature. Four hundred and twenty Mtwo instruments were used in the present study. Thirty new and 30 used instruments of each size were tested for cyclic fatigue in artificial canals with radii of curvature of 5 or 10 mm. Each instrument was rotated until fracture occurred and the number of cycles to fracture was calculated by multiplying time to fracture and rotational speed. Data were analysed using a t-test. According to the results of the study, radius of curvature was an important factor on cyclic fatigue resistance and clinical use significantly reduced the instrument lifespan.
authors: Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Ondokuz Mayis University, Samsun, Turkey. ugurinan29@hotmail.com
authors: Ugur
authors: U
authors: Inan
authors: Cumhur
authors: C
authors: Aydin
authors: Kadriye
authors: K
authors: Demirkaya
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000473:pathology; D055119:Elastic Modulus; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing; D009532:Nickel / Q000737:chemistry*; D018583:Pliability; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation*; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013242:Sterilization / Q000379:methods; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite