title: [Evaluation of the fracture of nickel-titanium rotary Protaper during root canal preparation].
abstract: OBJECTIVE
  To assess clinical application of Nickel-titanium(NiTi) rotary instruments Protaper in preparation of curved root canals.
  
  
  METHODS
  281 curved canals from 169 extracted molars were instrumented by Protaper rotary instruments using crown-down technique. An analysis was carried out regarding the relationship between the broken files and canal distribution,degree of curvature of canals, and the relationship between amount of the broken files and the duration was also included. SPSS18.0 software package was used for statistical analysis.
  
  
  RESULTS
  A total of 43 kits files were used in the preparation of 281 curved root canals, and broken files often happened in canals with curvature of >30° and very complex canals.
  
  
  CONCLUSIONS
  The fracture of NiTi instruments is closely related to the anatomy of the root cana1. With the use of NiTi rotary instruments Protaper, curved root canals can be prepared effectively. Meanwhile, the problem of instrument separation should be prevented.
authors.affiliation: Department of Stomatology, Changzheng Hospital, Second Military Medical University, Shanghai 200003, China. gxmjg@yahoo.com.cn
authors.forename: Ming-jin
authors.initials: MJ
authors.lastname: Gao
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Xiao-zhong
authors.initials: XZ
authors.lastname: Jiang
authors.forename: Li
authors.initials: L
authors.lastname: Liang
mesh_terms: D003722:Dental Alloys; D003786:Dental Pulp Cavity; D006801:Humans; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation; D014025:Titanium
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium