Adrenaline in local anaesthesia: the effect of concentration on dental pulpal circulation and anaesthesia

This study investigated the effects of inferior alveolar nerve block anaesthesia using 2% lignocaine with 1:100,000 or 1:80,000 adrenaline on pulpal blood flow in mandibular molar and canine teeth in 10 human subjects by laser Doppler flowmetry. The duration of pulpal anaesthesia in the teeth using electric pulp testing was also investigated. The injection of 2 ml of 2% lignocaine with 1:100,000 adrenaline caused a decrease in pulpal blood flow in both teeth in every subject. The mean pulpal blood flow in the canine tooth at 15 min was 58% of the baseline value whilst that in the molar was 76%. These values were not significantly different from the reduction in pulpal blood flow produced by 2% lignocaine with 1:80,000 adrenaline. Both solutions produced a reduction in blood flow that was of shorter duration than pulpal and soft tissue anaesthesia, and of shorter duration in the molar tooth compared with the canine. When 2% lignocaine with 1:100,000 adrenaline was injected, the mean reduction of blood flow was of shorter duration (canine, 60 min; molar, 42 min) than following 2% lignocaine with 1:80,000 adrenaline (canine, 93 min; molar, 72 min); these differences in reductions were statistically significant (P < 0.05). Using 2% lignocaine with 1:100,000 adrenaline, the mean duration of pulpal anaesthesia was 76 min in the canine tooth compared with 58 min in the molar tooth. Full soft tissue anaesthesia lasted for 117 min. These values were reduced significantly when compared with the lignocaine solution containing 1:80,000 adrenaline (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)