Effect of the topical application of 50% lignocaine hydrochloride on the sensitivity of dentine in man

Abstract

Objective: To determine the effect of topical applications of 50% (w/v) lignocaine HCl on the sensitivity of human dentine. Design: The experiments were carried out on 12 premolars scheduled for extraction as part of orthodontic treatment in nine subjects (ages: 16-29 years). Dentine was exposed by cutting a cavity at the tip of the buccal cusp of each tooth, and etched with 35% phosphoric acid. The sensitivity of the exposed dentine to probing and air-blast stimuli was assessed before and after applying either 50% (w/v) lignocaine HCl solution or distilled water to the exposed dentine for 10 min. Changes in the sensitivity of the dentine were monitored for up to 160 min. The subject indicated the intensity of any pain produced by marking a 100 mm visual analogue scale (VAS). Results: Before treatment, both forms of stimulus evoked pain in all the teeth. The median VAS score with probing was 40 mm and, with air-blast stimulation, 30 mm. 50% lignocaine HCl produced a progressive fall in these scores and after 30 min there was no response to either probing or air-blast stimulation. The responses started to return 30-160 min after the lignocaine had been washed off. Water had no effect. Conclusions: Lignocaine will diffuse into exposed dentine and block the pain evoked by probing and air-blast stimuli provided that a sufficiently steep diffusion gradient is created. A topical application of a 50% (w/v) solution of lignocaine HCl for 10 min will anaesthetise dentine within 30 min. © 2013 Elsevier Ltd. All rights reserved.