title: Effects of two nickel-titanium instrument systems, Mtwo versus ProTaper universal, on root canal geometry assessed by micro-computed tomography.
abstract: BACKGROUND
  The aim of this study was to compare the effects of Mtwo and ProTaper Universal (PTU) on root canal geometry three-dimensionally by using micro-computed tomography.
  
  
  METHODS
  A total of 20 canals were prepared with Mtwo or PTU system. Micro-computed tomography scanner was used to scan the specimens before and after instrumentation. Three-dimensional images were reconstructed. The parameters evaluated included canal surface area, volume, structure model index, thickness, straightening, canal transportation, and uninstrumented surface area.
  
  
  RESULTS
  Preparation significantly changed canal surface area, volume, structure model index, thickness, and canal curvature. There were no significant differences between instrument types concerning these parameters and uninstrumented surface area. The canals prepared with PTU showed larger values of transportation compared with those in Mtwo group at the apical third.
  
  
  CONCLUSIONS
  Both of the instrumentation systems produced canal preparations with adequate geometry. PTU produced larger transportation at apical third.
authors.affiliation: Key Laboratory for Oral Biomedical Engineering of Ministry of Education, School and Hospital of Stomatology, Wuhan University, Wuhan, China. Guobin.yang@163.com
authors.forename: Guobin
authors.initials: G
authors.lastname: Yang
authors.forename: Guohua
authors.initials: G
authors.lastname: Yuan
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Yun
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.forename: Bojin
authors.initials: B
authors.lastname: Liu
authors.forename: Hongkun
authors.initials: H
authors.lastname: Wu
mesh_terms: D003722:Dental Alloys; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional; D008963:Molar; D009532:Nickel; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium