Friday, September 13, 2013

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

Archives of Oral Biology
Volume 58, Issue 10 , Pages 1549-1555, October 2013

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 10min. Changes in the sensitivity of the dentine were monitored for up to 160min. The subject indicated the intensity of any pain produced by marking a 100mm visual analogue scale (VAS).

Results

Before treatment, both forms of stimulus evoked pain in all the teeth. The median VAS score with probing was 40mm and, with air-blast stimulation, 30mm. 50% lignocaine HCl produced a progressive fall in these scores and after 30min there was no response to either probing or air-blast stimulation. The responses started to return 30–160min 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 10min will anaesthetise dentine within 30min.

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