title: A photochemical method for in vitro evaluation of fluid flow in human dentine.
abstract: OBJECTIVE
  To evaluate the flow dynamics of dentine fluid using a chemiluminescence method in vitro.
  
  
  METHODS
  Horizontally sliced coronal dentine specimens with thicknesses of 1.4, 1.6, 1.8, and 2.0mm (n=10 each) were prepared from extracted human third molars. After cleaning with EDTA, a mounted specimen was clamped between 2 acrylic chambers attached to both the occlusal and pulpal sides. The occlusal chamber, which was closed with a glass coverslip, was filled with a chemiluminescent solution (0.02% luminol and 1% sodium hydroxide in water). A trigger solution of 1% hydrogen peroxide and 1% potassium ferricyanide was injected into the pulpal chamber at a constant pressure of 2.5 kPa, and allowed to immediately flow into the patent dentinal tubules. Four consecutive measurements (T1-T4) were performed on each sample by recording the emission of chemiluminescence with a photodetector. The relationship between the crossing time of the liquid through the slice and dentine thickness was examined.
  
  
  RESULTS
  An apparent time delay was detected between the starting points of the trigger solution run and photochemical emission at T1. Dt (Dt, s) values of each thickness group were 13.6 ± 4.25 for 1.4mm, 18.1 ± 2.38 for 1.6mm, 28.0 ± 2.46 for 1.8mm, and 39.2 ± 8.61 for 2.0mm, respectively. Dt significantly decreased as dentine became thinner towards the pulp chamber (P<0.001).
  
  
  CONCLUSIONS
  The velocity of fluid flow increased both with increasing dentine depth or reduction of remaining dentine thickness.
authors.affiliation: Division of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Miyagi, Japan; Endodontics Department of Dental College, Jazan University, Saudi Arabia.
authors.forename: Nezar
authors.initials: N
authors.lastname: Boreak
authors.affiliation: Division of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Miyagi, Japan. Electronic address: isi@m.tohoku.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ishihata
authors.affiliation: Division of Periodontology and Endodontology, Tohoku University Graduate School of Dentistry, 4-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Miyagi, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Shimauchi
mesh_terms: D003804:Dentin / Q000502:physiology*; D003806:Dentin Permeability / Q000502:physiology*; D019234:Dentinal Fluid / Q000502:physiology; D006801:Humans; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D012212:Rheology / Q000295:instrumentation*
keywords: Chemiluminescence; Dentinal fluid; Dentine permeability