Effects of adrenaline and felypressin (octapressin) on blood flow and sensory nerve activity in the tooth.

The present investigations in cats were designed to study the effects of local anaesthetics containing adrenaline and felypressin (octapressin) on dental pulp function. Intradental sensory nerve excitability was measured using electrodes placed in dentinal cavities in canine teeth. Changes in pulp blood flow were measured using the disappearance rate of a radioactive tracer placed in the same cavities. Injections (0.5 ml) of lidocaine (20 mg/ml) - adrenaline (12.5 microng/ml) or prilocaine (30 mg/ml) - octapressin (0.54 microng/ml) were given supraperiosteally in the apical area of the tooth. Adrenaline either alone or with lidocaine caused almost complete inhibition of pulp blood flow within a few minutes. This effect was followed by a total inhibition of the sensory nerve activity. In most cases there was a recovery of both functions after 3 hours. Octapressin, on the other hand, had no inhibitory effects on pulp blood flow or sensory nerve activity. Lidocaine and prilocaine were also without effect. These findings indicate a different mode of action of the two vasoconstrictors and suggest that octapressin may be preferred in infiltration anaesthesia during treatment of the vital tooth.