title: Cyclic fatigue resistance of rotary NiTi instruments after simulated clinical use in curved root canals.
abstract: The aim of this study was to assess cyclic fatigue resistance in rotary nickel-titanium instruments after simulated clinical use in curved root canals (40-degree, 5-mm radius curve). Thirty-six RaCe rotary NiTi files, size #5, taper 0.04, were divided into 3 groups: Groups A, B and C with one, three and five cycles of use, respectively. Time to failure was recorded with a stopwatch in seconds and subsequently converted to number of cycles to fracture. The data were analyzed statistically by ANOVA and Tukey's test (α=0.05). Five sets of clinically used files (group C) reached significantly lower cycle-numbers before fracture (mean=197.5 cycles) when compared with one set of clinically used files (mean=309.2) and three sets (mean=287.5). Results showed that the number of simulated clinical uses of RaCe instruments for shaping curved canals affects adversely the fatigue resistance of these instruments after five uses.
authors.affiliation: Discipline of Endodontics, Dental School, UFPA - Federal University of Pará, Belém, PA, Brazil. ofpessoa@ufpa.br
authors.forename: Oscar Faciola
authors.initials: OF
authors.lastname: Pessoa
authors.forename: Juliana Melo
authors.initials: JM
authors.lastname: da Silva
authors.forename: Giulio
authors.initials: G
authors.lastname: Gavini
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D004867:Equipment Design; D004868:Equipment Failure; D006801:Humans; D008953:Models, Anatomic; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation*; D012399:Rotation; D013314:Stress, Mechanical; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium