title: An ex vivo investigation of the relationship between apical root impedance and canal anatomy.
abstract: OBJECTIVE
  To investigate a possible relationship between apical root impedance and canal anatomy.
  
  
  METHODS
  Twenty-three roots from human extracted teeth with different apical anatomy (classified by number of apical canal exits) were selected. After impedance measurements, the root canals were stained and the teeth cleared to confirm their division into simple (S - Vertucci type 1; n=12) and complex (C - various Vertucci canal types with multiple exits; n=11) root types. Impedance measurements were taken using a frequency response analyser at seven apico-coronal levels in each root (0.0, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0 mm short of the apical terminus) at 14 frequencies ranging from 1120 to 100,000 Hz. Potential confounding factors were controlled. The impedance characteristics of individual roots were compared with 37 equivalent circuits to select best fit. The association between impedance characteristic (described by the selected equivalent circuit) and canal anatomy (S/C) was investigated using logistic regression with robust standard error to account for multiple data-sets from the same root.
  
  
  RESULTS
  Canal anatomy had a significant (P= 0.046) effect on the equivalent circuit model. One circuit (model 10) occurred significantly more commonly in the simple canals. The odds of selecting circuit-model-10 were 2.2 times (odds ratio 2.17, 95% confidence interval 1.01-4.63) higher in canals with simple anatomy compared to those with complex anatomy.
  
  
  CONCLUSIONS
  Canal anatomy had a significant effect on the equivalent circuit describing its impedance characteristics. It is theoretically possible to use impedance spectroscopy to clinically predict and image apical canal complexities.
authors.affiliation: Unit of Endodontology, Department of Restorative Dentistry, UCL Eastman Dental Institute, University College London, London, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Ardeshna
authors.forename: M
authors.initials: M
authors.lastname: Flanagan
authors.forename: Y-L
authors.initials: YL
authors.lastname: Ng
authors.forename: K
authors.initials: K
authors.lastname: Gulabivala
mesh_terms: D003786:Dental Pulp Cavity / Q000033:anatomy & histology*; D017097:Electric Impedance; D004582:Electronics, Medical / Q000295:instrumentation; D006801:Humans; D016017:Odds Ratio; D009811:Odontometry / Q000295:instrumentation*; D012390:Root Canal Therapy / Q000295:instrumentation*; D019227:Tooth Apex / Q000033:anatomy & histology*