title: Changes in centring and shaping ability using three  nickel–titanium instrumentation techniques  analysed by micro-computed tomography (μCT).
abstract: To compare the centring ability and the shaping ability of ProTaper (PT) files used in reciprocating motion and PT and Twisted Files (TF) used in continuous rotary motion, and to compare the volume changes obtained with the different instrumentation techniques using micro-computed tomography. Methodology Sixty mesial canals of thirty mandibular molars were randomly assigned to three instrumentation techniques: group 1, canals prepared with the PT series (up to F2) (n = 20); group 2, canals prepared with the F2 PT in reciprocating motion (n = 20); group 3 canals prepared with the TF series (size 25) (n = 20). Teeth were scanned pre- and postoperatively using micro-computed tomography to measure volume and shaping changes, and the obtained results were statistically analysed using parametric tests. Results The increase in canal volume obtained with the three instrumentation techniques was not significantly different. Canals were transported mostly towards the mesial aspect in the apical- and mid-third of the roots, and towards the furcal aspect coronally. No difference in the transportation and centring ratio was found between the techniques. There was no significant difference between the times of instrumentation (TF: 62.5 ± 5.4 s; PT: 60.6 ± 3.9 s; and F2 PT file in reciprocating motion: 51.0 ± 3.3 s). Conclusions ProTaper files used in reciprocating motion and PT and TF used in continuous rotary motion were capable of producing centred preparations with no substantial procedural errors.
authors.affiliation: Department of Conservative Dentistry, King’s College London Dental Institute at Guy’s King’s College and St Thomas’ Hospitals, KCL, London, UK.
authors.forename: S
authors.initials: S
authors.lastname: Stern
authors.forename: S
authors.initials: S
authors.lastname: Patel
authors.forename: F
authors.initials: F
authors.lastname: Foschi
authors.forename: M
authors.initials: M
authors.lastname: Sherriff
authors.forename: F
authors.initials: F
authors.lastname: Mannocci
mesh_terms: D003722:Dental Alloys / Q000737:chemistry*; D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000648:ultrastructure*; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008422:Materials Testing; D008963:Molar / Q000000981:diagnostic imaging / Q000648:ultrastructure; D009068:Movement; D009532:Nickel / Q000737:chemistry*; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D012399:Rotation; D014025:Titanium / Q000737:chemistry*; D019227:Tooth Apex / Q000000981:diagnostic imaging / Q000648:ultrastructure; D014092:Tooth Root / Q000000981:diagnostic imaging / Q000648:ultrastructure; D055114:X-Ray Microtomography / Q000379:methods
chemical_list: D003722:Dental Alloys; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium