The effect of vibration on pain during local anaesthesia injections

BACKGROUND: The "gate control" theory suggests pain can be reduced by simultaneous activation of nerve fibres that conduct non-noxious stimuli. This study investigated the effects of vibration stimuli on pain experienced during local anaesthetic injections. METHODS: In a preliminary study, subjects were asked to rate anticipated and actual pain from regional anaesthetic injections in the oral cavity. A second study compared, within subjects, pain from injections with and without a simultaneous vibration stimulus. Both infiltration and block anaesthetic injection techniques were assessed. In each subject, two similar injections were given and with one, a vibration stimulus was randomly allocated. Injection pain was assessed by visual analogue scale and McGill pain descriptors. RESULTS: Both infiltration and block injections were painful (mean anticipated intensity: 31.25, actual: 17.82 mm on 100 mm scale). Pain intensity with and without vibration was 12.9 mm (range 0-67) and 22.2 mm (range 0-83) respectively (p = 0.00005, paired T-test), and this effect was seen with both infiltration (p = 0.032) and block anaesthetic (p = 0.0001) injection subgroups. Furthermore, compared to no vibration-stimulus injections, injections with vibration resulted in less pain descriptors chosen (p = 0.004), and the descriptors had a lower pain rating (p = 0.001). CONCLUSIONS: The results suggest that vibration can be used to decrease pain during dental local anaesthetic administration.