title: [Comparison of the shaping ability of reciprocating instruments in simulated S-shaped canals].
abstract: OBJECTIVE
  To evaluate the shaping ability of Reciproc, WaveOne,Mtwo and ProTaper instruments in simulated S-shaped root canals.
  
  
  METHODS
  A total of 40 simulated S-shaped resin blocks were divided randomly into four groups, each group was prepared with Reciproc (group A), WaveOne (group B), Mtwo (group C) and ProTaper (group D), respectively. The preparation time and reduction of working length after preparation were measured. Pre- and postoperative images were obtained by a scanner and superimposed using Photoshop. Changes of coronal curve and apical curve curvature, as well as material removal from the inner and outer canal wall at 10 points beginning 1 mm from the end point of the canal, were measured using ImageJ. Centering ability was determined, accordingly. The data were analyzed using the one-way ANOVA and Student-Newman-Keuls.
  
  
  RESULTS
  The preparation time of group A and group B were (42.1 ± 2.7) and (41.5 ± 3.2) s respectively, significantly less than that of group C and group D [(62.7 ± 2.8), (62.8 ± 5.2) s] (P < 0.05).Reductions of working length after preparation were not significantly different among the four groups (P > 0.05). Coronal curve curvature changes of group A, group B and group D were (4.69 ± 0.63)°, (4.15 ± 0.89)° and (4.13 ± 0.59)° respectively, significantly less than that of group C[(5.26 ± 0.70)°], P < 0.05. Apical curve curvature changes were not significantly different among the four groups (P > 0.05). At the 2 mm point, the centering ability of group A[ (-0.242 ± 0.042) mm], group B[(-0.191 ± 0.077) mm], and group D[(-0.272 ± 0.046) mm] was better than group C[(-0.343 ± 0.057 mm] significantly (P < 0.05). At the 3 mm and 4 mm point, the centering ability of group A and group B was better than group C and group D significantly (P < 0.05). Whilst at the 5 mm point, the centering ability of group D was better than group A and group B (P < 0.05).
  
  
  CONCLUSIONS
  Reciproc and WaveOne could complete preparation faster and could maintain the original S-shaped canal curvature better than Mtwo and ProTaper, especially in the apical part.
authors.affiliation: Department of Endodontics, Capital Medical University School of Stomatology, Beijing 100050, China.
authors.forename: Tongfei
authors.initials: T
authors.lastname: Shao
authors.affiliation: Department of Endodontics, Capital Medical University School of Stomatology, Beijing 100050, China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Hou
authors.affiliation: Department of Endodontics, Capital Medical University School of Stomatology, Beijing 100050, China. Email: houbenxiang@gmail.com.
authors.forename: Benxiang
authors.initials: B
authors.lastname: Hou
mesh_terms: D000704:Analysis of Variance; D003722:Dental Alloys; D003762:Dental Instruments; D003786:Dental Pulp Cavity; D004868:Equipment Failure; D006801:Humans; D009532:Nickel; D018915:Root Canal Preparation; D014025:Titanium
chemical_list: D003722:Dental Alloys; D009532:Nickel; D014025:Titanium