title: Comparative evaluation of rotary ProTaper, Profile, and conventional stepback technique on reduction in Enterococcus faecalis colony-forming units and vertical root fracture resistance of root canals.
abstract: OBJECTIVE
  The purpose of this in vitro study was to evaluate the effect of various root canal instrumentation techniques with different instrument tapers on cleaning efficacy and resultant vertical root fracture (VRF) strength of the roots.
  
  
  METHODS
  Fifty human mandibular first premolar roots were enlarged to ISO size 20, inoculated with Enterococcus faecalis [ATCC2912] for 72 hours and divided into 5 groups: group I: prepared with .02 taper hand instruments ISO size 40; group II: Profile .04 taper size 40; group III: Profile .06 taper size 40; group IV: ProTaper size F4; and group V (control group) further divided into: Va: with bacterial inoculation and no mechanical instrumentation; and Group Vb: neither bacterial inoculation nor mechanical instrumentation. Cleaning efficacy was evaluated in terms of reduction of colony forming units (CFUs). The VRF strength was evaluated using D11 spreader as wedge in an Instron testing machine.
  
  
  RESULTS
  Root canals instrumented with ProTaper and 6% Profile instruments showed maximum reduction in CFUs, with statistically insignificant difference between them. The VRF resistance decreased in all instrumented groups. The difference of VRF between 2% and 4% taper Profile groups was statistically insignificant (P = .195). One-way analysis of variance showed that canals instrumented with ProTaper F4 showed maximum reduction in VRF resistance compared with control uninstrumented group.
  
  
  CONCLUSIONS
  Profile 6% taper instruments offer the advantage of maximum debridement without significant reduction in root fracture resistance.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Centre for Dental Education and Research, All India Institute of Medical Sciences, New Delhi, India.
authors.forename: Mamta
authors.initials: M
authors.lastname: Singla
authors.forename: Vivek
authors.initials: V
authors.lastname: Aggarwal
authors.forename: Ajay
authors.initials: A
authors.lastname: Logani
authors.forename: Naseem
authors.initials: N
authors.lastname: Shah
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D015169:Colony Count, Microbial; D003646:Debridement / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D003762:Dental Instruments / Q000009:adverse effects*; D003786:Dental Pulp Cavity / Q000382:microbiology* / Q000601:surgery; D013293:Enterococcus faecalis / Q000302:isolation & purification; D004867:Equipment Design; D006801:Humans; D008334:Mandible; D018915:Root Canal Preparation / Q000009:adverse effects / Q000295:instrumentation*; D014082:Tooth Fractures / Q000209:etiology / Q000517:prevention & control*; D014092:Tooth Root / Q000293:injuries / Q000382:microbiology / Q000601:surgery