To determine the effect of topical applications of 50% (w/v) lignocaine HCl on the sensitivity of human dentine.
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).
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.
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.