title: The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effects of smear layer and canal instrumentation on leakage in root-filled teeth.
  
  
  METHODS
  Six groups (n = 12) of freshly extracted human canines and premolars with closed apices and single roots were used. Groups A, B, C, and D were instrumented with engine-driven rotary nickel-titanium MCXIM files and Groups E and F were instrumented with conventional stainless steel hand files. Groups A, C, and E were flushed with 3.0 mL of 17.0% REDTA to remove the smear layer prior to obturation. All teeth were flushed with 5.25% NaOCl, then obturated with AH-26 sealer and either the lateral condensation (Groups C-E) or thermomechanical compaction technique (Groups A and B). Copper wire was placed coronally in contact with the gutta-percha in each tooth and, after immersion in 0.9% NaCl solution, a 10 volt dc voltage was connected between each tooth and a stainless steel electrode. The current flow in the circuit was observed for 45 days. One way ANOVA and Duncan's Multiple Range Test were used to compare Groups A-F at time intervals of 10, 20, 30 and 45 days and identify statistically significant differences.
  
  
  RESULTS
  Significantly less microleakage occurred when the smear layer was removed and when the canals were obturated with thermoplasticized gutta-percha. Canals instrumented with engine-driven NiTi files exhibited less leakage than hand-instrumented canals irrespective of obturation method.
  
  
  CONCLUSIONS
  Smear layer removal is beneficial to root canal sealing. Obturation with thermoplasticized gutta-percha provides a superior seal whilst canal instrumentation with engine-driven NiTi files reduces the extent of microleakage in root canals.
authors: School of Dentistry, University of Maryland, Baltimore, 666 West Baltimore Street, Baltimore, MD 21201, USA. AVF001@dental.umaryland.edu
authors: J A
authors: JA
authors: von Fraunhofer
authors: D K
authors: DK
authors: Fagundes
authors: N J
authors: NJ
authors: McDonald
authors: T C
authors: TC
authors: Dumsha
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D001729:Bismuth / Q000627:therapeutic use; D002593:Cetrimonium Compounds / Q000627:therapeutic use; D002614:Chelating Agents / Q000627:therapeutic use; D003481:Cuspid; D003722:Dental Alloys; D003763:Dental Leakage / Q000145:classification*; D004202:Disinfectants / Q000627:therapeutic use; D004338:Drug Combinations; D004492:Edetic Acid / Q000627:therapeutic use; D004563:Electrochemistry; D004853:Epoxy Resins; D004867:Equipment Design; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D008709:Methenamine / Q000627:therapeutic use; D009532:Nickel; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012388:Root Canal Irrigants / Q000627:therapeutic use; D012389:Root Canal Obturation; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012390:Root Canal Therapy; D012834:Silver / Q000627:therapeutic use; D016369:Smear Layer; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013193:Stainless Steel; D013223:Statistics as Topic; D014025:Titanium / Q000627:therapeutic use
chemical_list: D002593:Cetrimonium Compounds; D002614:Chelating Agents; D003722:Dental Alloys; D004202:Disinfectants; D004338:Drug Combinations; D004853:Epoxy Resins; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; C040654:titanium nickelide; D013193:Stainless Steel; D012834:Silver; C028044:epoxy resin AH-26; C031883:REDTA; D009532:Nickel; D006171:Gutta-Percha; D004492:Edetic Acid; D014025:Titanium; D012973:Sodium Hypochlorite; D008709:Methenamine; D001729:Bismuth