An investigation of the effect on 27-gauge needle tips following a single local anaesthetic injection.

One hundred and forty one, 27-gauge local anaesthetic needles were collected, each following a single injection of local anaesthetic using four commonly performed local anaesthetic injection techniques. The needles were examined for needle tip damage under the scanning electron microscope. Ten unused needles were used as controls. Bone was contacted in 75 (59%) instances and, of these, 73 (97.3%) showed needle tip deformity. Of the four techniques used, bone contact was commonest with the inferior alveolar nerve block, occurring in 88% of instances.