title: The influence of preparation technique and sodium hypochlorite on removal of pulp and predentine from root canals of posterior teeth.
abstract: OBJECTIVE
  To test the null hypothesis that removal of pulp tissue and predentine from root canals of multirooted teeth is not significantly different when performed by one of two mechanical preparation techniques in conjunction with either water or 3% sodium hypochlorite (NaOCl) irrigation.
  
  
  METHODS
  Forty-six freshly extracted premolar or molar teeth, with pulps vital at the time of extraction, were assigned to four groups balanced by anatomy (group 1, step-back filing/NaOCl; group 2, step-back filing/water; group 3, automated rotary/NaOCl; group 4, automated rotary/water). Preparation was undertaken by a single operator and the volumes of irrigant recorded for each tooth. One root from each tooth was prepared for transverse histological assessment at eight levels, including one at and two apical to the working length. A validated index was used to measure the presence and location of residual pulp tissue and predentine.
  
  
  RESULTS
  No statistically significant differences were found in the frequency with which residual pulp tissue or predentine were observed amongst the groups. Coronal parts were more frequently devoid of pulp tissue and predentine than the apical. Canals were frequently occluded with residual pulp tissue apical to the working length. There was a trend for better pulp and predentine removal in accessible parts of the canal as a function of rotary preparation and NaOCl irrigation. The isthmus had residual pulp tissue less frequently in the NaOCl groups. Accessory anatomy was unaffected regardless of technique or irrigant.
  
  
  CONCLUSIONS
  Pulp tissue and predentine removal were not significantly different between a step-back filing and an automated rotary preparation technique in conjunction with water or NaOCl.
authors.affiliation: Department of Conservative Dentistry, Eastman Dental Institute for Oral Health Care Sciences, University College, London, London, UK.
authors.forename: G E
authors.initials: GE
authors.lastname: Evans
authors.forename: P M
authors.initials: PM
authors.lastname: Speight
authors.forename: K
authors.initials: K
authors.lastname: Gulabivala
mesh_terms: D001641:Bicuspid; D016009:Chi-Square Distribution; D003782:Dental Pulp / Q000187:drug effects / Q000648:ultrastructure*; D003786:Dental Pulp Cavity / Q000187:drug effects / Q000648:ultrastructure*; D003804:Dentin / Q000187:drug effects / Q000648:ultrastructure*; D004202:Disinfectants / Q000627:therapeutic use*; D006801:Humans; D008963:Molar; D015588:Observer Variation; D015203:Reproducibility of Results; D012388:Root Canal Irrigants / Q000627:therapeutic use*; D018915:Root Canal Preparation / Q000295:instrumentation / Q000379:methods*; D012973:Sodium Hypochlorite / Q000627:therapeutic use*; D019227:Tooth Apex / Q000648:ultrastructure; D019228:Tooth Crown / Q000648:ultrastructure; D014092:Tooth Root / Q000648:ultrastructure; D014867:Water
chemical_list: D004202:Disinfectants; D012388:Root Canal Irrigants; D014867:Water; D012973:Sodium Hypochlorite