title: The effect of pulpward pressure on the response to 50% lidocaine (lignocaine) applied to exposed dentine in cats.
abstract: The responses of intradental nerves can be blocked by 50% lidocaine applied to exposed, etched dentine. The aim here was to analyse electrophysiologically the contribution of pulpward pressure to the anaesthetic effect of lidocaine applied to exposed dentine. In 17 adult cats with intact lower canines, approximately 1mm of the coronal tip of the canine was removed and the exposed dentine acid-etched. Pulpward pressure was applied to the exposed dentine through a chamber fixed to the tip of the tooth. Cervical and coronal electrodes of silver wire and Ag/AgCl mixture were placed, the cervical 2mm from the gingival margin of the canine and the coronal into the coronal pulp chamber. The inferior alveolar nerve was surgically exposed and single pulpal nerve fibres responding to electrical stimulation of the canine were identified. The chamber was filled with 50% lidocaine solution, and 0 (atmospheric pressure), 1.3, 5.0 or 10.0 kPa pressure was applied to the chamber for 20 min. Orthodromic and antidromic action potentials were compared before and after the lidocaine application. When lidocaine was applied at 0, 1.3 or 5.0 kPa (n=5 each) for 20 min, all the orthodromic responses to cathodal electrical stimulation with the coronal electrode were blocked. Almost all orthodromic responses (12/15) remained unblocked when the cathodal electrical stimulation was applied with the cervical electrode. Applying 10.0 kPa pressure to the lidocaine solution blocked all the pulpal nerve responses (n=5) to both stimulation modes. The amplitude of the antidromic compound action potential was significantly decreased when the applied pressure was increased. These results suggest that increased pulpward pressure may effectively force anaesthetic solution more rapidly through the dentinal tubules into the pulp.
authors.affiliation: Pulp Biology and Endodontics, Department of Restorative Sciences, Graduate School, Tokyo Medical and Dental University, 5-45 Yushima 1-Chome, Bunkyo-ku, 113-8549 Tokyo, Japan. masahiko.endo@tmd.ac.jp
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ozawa
authors.forename: Hideharu
authors.initials: H
authors.lastname: Ikeda
authors.forename: Hideaki
authors.initials: H
authors.lastname: Suda
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000704:Analysis of Variance; D000779:Anesthetics, Local / Q000008:administration & dosage*; D000818:Animals; D002415:Cats; D003782:Dental Pulp / Q000294:innervation* / Q000502:physiology; D003804:Dentin / Q000187:drug effects; D003806:Dentin Permeability; D019234:Dentinal Fluid / Q000502:physiology*; D006874:Hydrostatic Pressure; D008012:Lidocaine / Q000008:administration & dosage*; D008340:Mandibular Nerve / Q000187:drug effects*; D009412:Nerve Fibers / Q000187:drug effects; D009431:Neural Conduction / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine