The effect of replacing dental needles between subsequent inferior alveolar nerve blocks on pain and trismus - a double blinded, randomised split-mouth study.

Background: Inferior alveolar Nerve Blocks are widely used in dental practice for achieving anaesthesia in the mandibular teeth. It is widely accepted that in order for this type of injection to be effective, the needle needs to penetrate a substantial depth of soft tissues as well as make contact with bone. This routinely leads to both blunting and barbing of the needle tip suggesting that a needle change is preferable for any subsequent injection as this will result in less tissue damage and pain for patient's. The study aimed to verify whether a change in needle affected measures of pain and trismus. Material and Methods: This was a prospective, single center, double blinded (both clinician and participant), randomized, split-mouth study conducted in a large dental hospital and teaching facility. Participants were screened for factors that might alter their head pain sensation and participated in 2 clinical visits. In the first visit 2 needle insertions either with/without needle change were performed without anaesthetic as per an IANB injection. A survey instrument was used to capture several dimensions of pain both immediately after the visit as well as 48-72 hours later. This method was repeated on a second visit on the opposite mandibular quadrant after a washout period of at least 2 weeks. Paired t-Test's were performed at the 2 time points. Results: Significance was only demonstrated in one of 10 sensory and 12 emotional pain descriptors during one of the 2 time points of measurement. Similarly, VAS mean pain scores and a measure of trismus were not affected by needle change. Conclusions: This study was able to demonstrate that a change in needle between subsequent IANB's does not affect self-reported measures of pain nor trismus.