title: What happens to unprepared root canal walls: a correlative analysis using micro-computed tomography and histology/scanning electron microscopy.
abstract: OBJECTIVE
  To microscopically examine the cleanliness of root canal walls that remained unprepared as revealed by micro-CT.
  
  
  METHODS
  The root canals of 10 freshly extracted mandibular premolars with necrotic pulps and apical periodontitis along with the mesiobuccal canals of 11 mandibular molars with vital pulps were prepared using Reciproc instruments R40 and R25, respectively, and 2.5% sodium hypochlorite irrigation. Specimens were scanned in micro-CT before and after preparation, and the unprepared areas were identified. The outer root surface corresponding to the untouched areas was marked on each root third to guide further analysis using histological (for teeth with vital pulps) and scanning electron microscopic (SEM; for necrotic teeth) examination. In the teeth with vital pulps, the root canal area occupied by tissue remnants was calculated. In SEM analysis of teeth with necrotic pulps, scores were attributed for the amount of debris on the untouched areas.
  
  
  RESULTS
  The proportion of unprepared areas in the mesiobuccal molar canals was 18.1% and 9.6% over the full canal length and apical canal, respectively. In premolars, corresponding figures were 34.6% and 17.6%, respectively. Histological analysis of canals with vital pulps revealed tissue remnants over the untouched walls almost exclusively in the apical canal. SEM analysis of the canals with necrotic pulps revealed debris along the untouched walls in all root canal thirds.
  
  
  CONCLUSIONS
  The areas that remain untouched by Reciproc instruments used with 2.5% NaOCl irrigation as revealed by micro-CT analysis were usually covered with debris, in the form of pulp tissue remnants, bacteria and dentine chips, especially in the apical root canal.
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: J F
authors.initials: JF
authors.lastname: Siqueira
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: A R
authors.initials: AR
authors.lastname: Pérez
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: M F
authors.initials: MF
authors.lastname: Marceliano-Alves
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: J C
authors.initials: JC
authors.lastname: Provenzano
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: S G
authors.initials: SG
authors.lastname: Silva
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: F R
authors.initials: FR
authors.lastname: Pires
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: G C S
authors.initials: GCS
authors.lastname: Vieira
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: I N
authors.initials: IN
authors.lastname: Rôças
authors.affiliation: Department of Endodontics, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: F R F
authors.identifier: http://orcid.org/0000-0002-9922-8202
authors.initials: FRF
authors.lastname: Alves
mesh_terms: D003786:Dental Pulp Cavity / Q000000981:diagnostic imaging / Q000473:pathology* / Q000648:ultrastructure; D003790:Dental Pulp Necrosis / Q000473:pathology; D006801:Humans; D008855:Microscopy, Electron, Scanning; D010485:Periapical Periodontitis / Q000473:pathology; D018915:Root Canal Preparation; D055114:X-Ray Microtomography
keywords: cleaning and shaping; endodontic treatment; histology; micro-computed tomography; scanning electron microscopy