Effect of palatal injections on pulpal blood flow in premolars

The effect of palatal infiltration injections using 2% lignocaine hydrochloride with 1:80,000 adrenaline was evaluated for sound maxillary first premolar teeth. The influence of the injections on pulpal blood flow and local anaesthesia was investigated. Ten human volunteers were given the following injections on different days: 1 ml palatal infiltration; 1 ml buccal infiltration; 1 ml palatal and 1 ml buccal infiltration; and 2 ml buccal infiltration. The blood flow was observed with a laser Doppler flowmeter with the probes held against the buccal surfaces of the teeth by a splint. Blood flow was recorded digitally on a computer in machine units. Pulpal anaesthesia was assessed using a monopolar electric pulp tester. All injections significantly reduced blood flow from baseline levels (p<0.05). The 1-ml palatal injection produced a significantly longer period of reduced blood flow (mean 40 min) compared with the other injections (p<0.05). The duration of blood flow reduction was shorter than the duration of pulpal anaesthesia for every injection. Only seven out of 10 palatal injections achieved pulpal anaesthesia. The 2-ml buccal injection and the combined buccal and palatal injections produced significantly longer anaesthesia than the 1-ml buccal injection (p<0.05).