title: [Experimental study of preparing curved root canals with different instrument].
abstract: OBJECTIVE
  To compare the shaping ability and the influence on apical foramen among hand ProTaper, stainless steel K-files and rotary ProTaper in preparing different curved root canal.
  
  
  METHODS
  Forty simulated resin root canal blocks were randomly divided into four groups and prepared by hand ProTaper, stainless steel K-file and rotary ProTaper, respectively. Of them, 12 blocks in group A, B, C consist of six 200 curved root canals and six 30 degrees curved root canals each group. The curvature of the other 4 blocks in group D was less than 5 degrees. Taking photos of the models to the root canal orthotopically and apical foramen using digital camera before and after instrumentation. Finally, the transportation of root canal and the size of apical foramen were analyzed using special image software Auto-CAD.
  
  
  RESULTS
  The transportation of center in group B was the highest than that in group A and group C (P<0.05). In some portions of root canal, the transportation of center in group C was higher than that in group A. The size of the apical foramen in group B was significantly bigger than the other groups and the size of the apical foramen in 30 degrees root canal was significantly bigger than that in 20 degrees root canal after instrumentation (P<0.05). There was no significantly different between group A and group C, though the size of apical foramen in group C was bigger than that in group A at the same curvature, and that in 30 degrees root canal was bigger than in 20 degrees root canal (P>0.05).
  
  
  CONCLUSIONS
  Both of the two instruments engender root canal transportation, and curvature is the main reason of transportation. Comparing with stainless steel K-files, NiTi files can maintain the shape of the root canal and apical foramen well.
authors.affiliation: Dept. of Stomatology, Xiangya Hospital, Central South University, Changsha 410008, China.
authors.forename: Ling-yun
authors.initials: LY
authors.lastname: Yin
authors.forename: Xiao-li
authors.initials: XL
authors.lastname: Xie
authors.forename: Min-min
authors.initials: MM
authors.lastname: Chen
authors.forename: Liu-hui
authors.initials: LH
authors.lastname: Liu
authors.forename: Tian-you
authors.initials: TY
authors.lastname: Ling
mesh_terms: D003786:Dental Pulp Cavity; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation; D012390:Root Canal Therapy; D013193:Stainless Steel; D014025:Titanium; D019227:Tooth Apex
chemical_list: D013193:Stainless Steel; D009532:Nickel; D014025:Titanium