title: Micro-CT analyses of apical enlargement and molar root canal complexity.
abstract: OBJECTIVE
  To compare the effectiveness of two rotary hybrid instrumentation techniques with focus on apical enlargement in molar teeth and to quantify and visualize spatial details of instrumentation efficacy in root canals of different complexity.
  
  
  METHODS
  Maxillary and mandibular molar teeth were scanned using X-ray microcomputed tomography. Root canals were prepared using either a GT/Profile protocol or a RaCe/NiTi protocol. Variables used for evaluation were the following: distance between root canal surfaces before and after preparation (distance after preparation, DAP), percentage of root canal area remaining unprepared and increase in canal volume after preparation. Root canals were classified according to size and complexity, and consequences of unprepared portions of narrow root canals and intraradicular connections/isthmuses were included in the analyses. One- and two-way anova were used in the statistical analyses.
  
  
  RESULTS
  No difference was found between the two techniques: DAP(apical-third) (P = 0.590), area unprepared(apical-third) (P = 0.126) and volume increase(apical-third) (P = 0.821). Unprepared root canal area became larger in relation to root canal size and complexity, irrespective of the technique used. Percentage of root canal area remaining unprepared was significantly lower in small root canals and complex systems compared to large root canals. The isthmus area per se contributed with a mean of 17.6%, and with a mean of 25.7%, when a narrow root canal remained unprepared.
  
  
  CONCLUSIONS
  The addition of isthmuses did not significantly alter the ratio of instrumented to unprepared areas at total root canal level. Distal and palatal root canals had the highest level of unprepared area irrespective of the two instrumentation techniques examined.
authors: Department of Cariology and Endodontics, School of Dentistry, University of Copenhagen, Copenhagen. merma@sund.ku.dk
authors: M
authors: M
authors: Markvart
authors: T A
authors: TA
authors: Darvann
authors: P
authors: P
authors: Larsen
authors: M
authors: M
authors: Dalstra
authors: S
authors: S
authors: Kreiborg
authors: L
authors: L
authors: Bjørndal
mesh_terms: D003722:Dental Alloys / Q000737:chemistry; D003782:Dental Pulp / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D003804:Dentin / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D004867:Equipment Design; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D008963:Molar / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D009532:Nickel / Q000737:chemistry; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods / Q000592:standards; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D014025:Titanium / Q000737:chemistry; D019227:Tooth Apex / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D003722:Dental Alloys; D012388:Root Canal Irrigants; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium; D012973:Sodium Hypochlorite