title: Reduction in intracanal bacteria during root canal preparation with and without apical enlargement.
abstract: OBJECTIVE
  To compare in vitro intracanal bacterial reduction using nickel-titanium rotary instruments with and without apical enlargement.
  
  
  METHODS
  Thirty-eight palatal roots of maxillary molar teeth, with mature apices were subdivided according to lengths and then randomly assigned to two experimental and one control groups. The roots were sterilized and then reinfected with Enterococcus faecalis, which served as a bacteriological marker. All roots in the experimental groups were prepared in a step-down sequence with engine-driven GT rotary files at 350 rpm. In experimental group A (n = 16) additional apical enlargement to ISO size 35 was performed. In group B (n = 16) a serial step-back technique was followed with no apical enlargement. This was combined in groups A and B with irrigation with NaOCl and EDTA. In the control group (group C, n = 6) irrigation only was carried out, with no mechanical preparation. Samples were then taken from the root canals to determine the numbers of remaining bacteria.
  
  
  RESULTS
  In groups A and B, 15 (94%) and 13 (81%) specimens were rendered bacteria-free, respectively. In the control group C none of the specimens were bacteria-free. There was a significant difference (P < 0.001) in the antibacterial effects of experimental and control regimens. There was, however, no significant difference (P = 0.276) between the preparation methods used in the experimental groups.
  
  
  CONCLUSIONS
  There was no significant difference in intracanal bacterial reduction when Ni-Ti GT rotary preparation with NaOCl and EDTA irrigation was used with or without apical enlargement preparation technique. It may therefore not be necessary to remove dentine in the apical part of the root canal when a suitable coronal taper is achieved to allow satisfactory irrigation of the root canal system with antimicrobial agents.
authors.affiliation: Dental School, University of Glasgow, UK.
authors.forename: L G
authors.initials: LG
authors.lastname: Coldero
authors.forename: S
authors.initials: S
authors.lastname: McHugh
authors.forename: D
authors.initials: D
authors.lastname: MacKenzie
authors.forename: W P
authors.initials: WP
authors.lastname: Saunders
mesh_terms: D000704:Analysis of Variance; D002614:Chelating Agents / Q000627:therapeutic use; D015169:Colony Count, Microbial; D016001:Confidence Intervals; D003722:Dental Alloys; D003786:Dental Pulp Cavity / Q000382:microbiology* / Q000648:ultrastructure; D003804:Dentin / Q000648:ultrastructure; D004202:Disinfectants / Q000627:therapeutic use; D004492:Edetic Acid / Q000627:therapeutic use; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification*; D004867:Equipment Design; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008855:Microscopy, Electron, Scanning; D008963:Molar; D009532:Nickel; D010865:Pilot Projects; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013223:Statistics as Topic; D013885:Thiosulfates / Q000627:therapeutic use; D014025:Titanium; D019227:Tooth Apex / Q000648:ultrastructure*
chemical_list: D002614:Chelating Agents; D003722:Dental Alloys; D004202:Disinfectants; D012388:Root Canal Irrigants; D013885:Thiosulfates; C040654:titanium nickelide; D009532:Nickel; D004492:Edetic Acid; D014025:Titanium; D012973:Sodium Hypochlorite; C017717:sodium thiosulfate