Effect of inferior alveolar nerve block anaesthesia on the lower teeth

The aims of this study were to investigate the effects on pulpal blood flow and anaesthesia in mandibular teeth during inferior alveolar nerve block anaesthesia using 2% lignocaine with 1:80,000 adrenaline in 10 adult human subjects. Local anaesthetic solution was delivered close to the inferior alveolar nerve at the mandibular foramen using a standardized nerve block technique. The pulpal blood flow of the canine and first permanent molar was monitored by a laser Doppler flowmeter. At selected times pulpal anaesthesia was tested with an electric pulp tester. The injection of 2 ml of solution caused a decrease in pulpal blood flow in both teeth in every subject. The reduction in blood flow was of shorter duration than pulpal and soft tissue anaesthesia. A period of increased blood flow following the period of reduction was noted in several subjects. The mean reduction in pulpal blood flow in the canine at 15 min was 48% and lasted for a mean of 93 min. In contrast, the mean reduction in pulpal blood flow in the molar at 15 min was 25% and of 72 min mean duration. The mean duration of pulpal anaesthesia was 114 min in the canine compared with 88 min in the molar. Full soft tissue anaesthesia lasted for a mean of 151 min, whereas complete recovery took 255 min. This study indicated that lignocaine and adrenaline in block anaesthesia acted not only at the site of injection but also within the individual teeth.