title: A Comparison of Apical Bacterial Extrusion in Manual, ProTaper Rotary, and One Shape Rotary Instrumentation Techniques.
abstract: BACKGROUND
  Apical extrusion of irrigants and debris is an inherent limitation associated with cleaning and shaping of root canals and has been studied extensively because of its clinical relevance as a cause of flare-ups. Many factors affect the amount of extruded intracanal materials. The purpose of this study was to assess the bacterial extrusion by using manual, multiple-file continuous rotary system (ProTaper) and single-file continuous rotary system (One Shape).
  
  
  METHODS
  Forty-two human mandibular premolars were inoculated with Enterococcus faecalis by using a bacterial extrusion model. The teeth were divided into 3 experimental groups (n = 12) and 1 control group (n = 6). The root canals of experimental groups were instrumented according to the manufacturers' instructions by using manual technique, ProTaper rotary system, or One Shape rotary system. Sterilized saline was used as an irrigant, and bacterial extrusion was quantified as colony-forming units/milliliter. The results obtained were statistically analyzed by using one-way analysis of variance for intergroup comparison and post hoc Tukey test for pair-wise comparison. The level for accepting statistical significance was set at P < .05.
  
  
  RESULTS
  All the instrumentation techniques resulted in bacterial extrusion, with manual step-back technique exhibiting significantly more bacterial extrusion than the engine-driven systems. Of the 2 engine-driven systems, ProTaper rotary extruded significantly more bacteria than One Shape rotary system (P < .05).
  
  
  CONCLUSIONS
  The engine-driven nickel-titanium systems were associated with less apical extrusion. The instrument design may play a role in amount of extrusion.
authors.affiliation: Department of Conservative Dentistry and Endodontics, Sudha Rustogi College of Dental Sciences and Research, Faridabad, Haryana, India.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Mittal
authors.affiliation: Department of Conservative Dentistry and Endodontics, Sudha Rustogi College of Dental Sciences and Research, Faridabad, Haryana, India.
authors.forename: Meenu G
authors.initials: MG
authors.lastname: Singla
authors.affiliation: Department of Conservative Dentistry and Endodontics, Sudha Rustogi College of Dental Sciences and Research, Faridabad, Haryana, India.
authors.forename: Ashima
authors.initials: A
authors.lastname: Garg
authors.affiliation: Department of Conservative Dentistry and Endodontics, Sudha Rustogi College of Dental Sciences and Research, Faridabad, Haryana, India. Electronic address: dr.anu53@gmail.com.
authors.forename: Anu
authors.initials: A
authors.lastname: Dhawan
mesh_terms: D001641:Bicuspid / Q000382:microbiology; D013293:Enterococcus faecalis; D006801:Humans; D008334:Mandible; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D019227:Tooth Apex / Q000382:microbiology*
keywords: Apical extrusion; One Shape; ProTaper; step-back