title: Flat-oval root canal preparation with self-adjusting file instrument: a micro-computed tomography study.
abstract: BACKGROUND
  The aim of this study was to evaluate the root canal preparation in flat-oval canals treated with either rotary or self-adjusting file (SAF) by using micro-tomography analysis.
  
  
  METHODS
  Forty mandibular incisors were scanned before and after root canal instrumentation with rotary instruments (n = 20) or SAF (n = 20). Changes in canal volume, surface area, and cross-sectional geometry were compared with preoperative values. Data were compared by independent sample t test and χ(2) test between groups and paired sample t test within the group (α = 0.05).
  
  
  RESULTS
  Overall, area, perimeter, roundness, and major and minor diameters revealed no statistical difference between groups (P > .05). In the coronal third, percentage of prepared root canal walls and mean increases of volume and area were significantly higher with SAF (92.0%, 1.44 ± 0.49 mm(3), 0.40 ± 0.14 mm(2), respectively) than rotary instrumentation (62.0%, 0.81 ± 0.45 mm(3), 0.23 ± 0.15 mm(2), respectively) (P < .05). SAF removed dentin layer from all around the canal, whereas rotary instrumentation showed substantial untouched areas.
  
  
  CONCLUSIONS
  In the coronal third, mean increases of area and volume of the canal as well as the percentage of prepared walls were significantly higher with SAF than with rotary instrumentation. By using SAF instruments, flat-oval canals were homogenously and circumferentially prepared. The size of the SAF preparation in the apical third of the canal was equivalent to those prepared with #40 rotary file with a 0.02 taper.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Marco Aurélio
authors.initials: MA
authors.lastname: Versiani
authors.forename: Jesus Djalma
authors.initials: JD
authors.lastname: Pécora
authors.forename: Manoel Damião
authors.initials: MD
authors.lastname: de Sousa-Neto
mesh_terms: D003762:Dental Instruments; D003786:Dental Pulp Cavity / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D004867:Equipment Design; D006801:Humans; D007180:Incisor / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery; D008334:Mandible; D015203:Reproducibility of Results; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D055114:X-Ray Microtomography