title: Facilitatory effect of AC-iontophoresis of lidocaine hydrochloride on the permeability of human enamel and dentine in extracted teeth.
abstract: OBJECTIVE
  The objectives of the present study were to quantitatively evaluate chemical permeability through human enamel/dentine using conductometry and to clarify if alternating current (AC) iontophoresis facilitates such permeability.
  
  
  METHODS
  Electrical impedance of different concentrations of lidocaine hydrochloride was measured using a bipolar platinum impedance probe. A quadratic curve closely fitted to the response functions between conductance and lidocaine hydrochloride. For analysis of the passage of lidocaine hydrochloride through human enamel/dentine, eight premolars that were extracted for orthodontic treatment were sectioned at the cemento-enamel junction. The tooth crowns were held between two chambers with a double O-ring. The enamel-side chamber was filled with lidocaine hydrochloride, and the pulp-side chamber was filled with extrapure water. Two platinum plate electrodes were set at the end of each chamber to pass alternating current. A simulated interstitial pulp pressure was applied to the pulp-side chamber. The change in the concentration of lidocaine hydrochloride in the pulp-side chamber was measured every 2min using a platinum recording probe positioned at the centre of the pulp-side chamber. Passive entry without iontophoresis was used as a control.
  
  
  RESULTS
  The level of lidocaine hydrochloride that passed through enamel/dentine against the dentinal fluid flow increased with time. Electrical conductance (G, mho) correlated closely to the concentration (x, mmol/L) of lidocaine hydrochloride (G=2.16x(2)+0.0289x+0.000376, r(2)=0.999).
  
  
  CONCLUSIONS
  Lidocaine hydrochloride can pass through enamel/dentine. Conductometry showed that the level of lidocaine hydrochloride that passed through enamel/dentine was increased by AC iontophoresis.
authors.affiliation: Pulp Biology and Endodontics, Department of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Japan. hms-ikeda.endo@tmd.ac.jp
authors.forename: Hideharu
authors.initials: H
authors.lastname: Ikeda
authors.forename: Hideaki
authors.initials: H
authors.lastname: Suda
mesh_terms: D001641:Bicuspid; D003217:Conductometry / Q000379:methods; D003743:Dental Enamel / Q000737:chemistry / Q000187:drug effects*; D003804:Dentin / Q000737:chemistry / Q000187:drug effects*; D003806:Dentin Permeability / Q000187:drug effects*; D006801:Humans; D007478:Iontophoresis / Q000379:methods*; D008012:Lidocaine / Q000494:pharmacology*; D041623:Tomography, Optical Coherence / Q000379:methods; D019228:Tooth Crown / Q000737:chemistry
chemical_list: D008012:Lidocaine