title: Shaping ability of nickel-titanium rotary instruments in simulated S-shaped root canals.
abstract: OBJECTIVE
  The aim of this study was to compare the shaping ability of 4 nickel-titanium rotary techniques and 1 hand technique in simulated S-shaped curved root canals.
  
  
  METHODS
  Seventy-five simulated double-curved resin root canals were divided into 5 groups (n = 15). The canals were compared at 12 different levels and at 3 different times: before preparation and after preparation to master apical 25 and 35. Data were statistically analyzed by performing 2-by-2 comparisons with the Tukey parametric test of variance analysis using a confidence interval of 95%.
  
  
  RESULTS
  All of the 75 resin blocks presented transportation of the root canals by transforming the apical curvature into a straight zone and straightening the first curvature. When increasing the diameter from 25 to 35, both curvatures were straightened.
  
  
  CONCLUSIONS
  Based on the conditions of this study, we can say that the flexibility of the instruments is inversely related with the transportation of the root canals, and that in the double-curved root canals, the apical curvature is always straightened.
authors.affiliation: Centro de Investigação em Ciências da Saúde, Instituto Superior de Ciências da Saúde-Norte, CESPU, Gandra, Portugal. ruimad@sapo.pt
authors.forename: Rui Gonçalves
authors.initials: RG
authors.lastname: Madureira
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Forner Navarro
authors.forename: Mari Carmen
authors.initials: MC
authors.lastname: Llena
authors.forename: Marcia
authors.initials: M
authors.lastname: Costa
mesh_terms: D000704:Analysis of Variance; D003722:Dental Alloys; D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D003799:Dental Stress Analysis; D004868:Equipment Failure; D006801:Humans; D003765:Models, Dental; D009532:Nickel; D016011:Normal Distribution; D018583:Pliability; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods*; D013193:Stainless Steel; D014025:Titanium; D014092:Tooth Root / Q000033:anatomy & histology*
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium