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Influence of anesthetic flow rate delivered by the Wand Local Anesthetic System on pain response to palatal injections.

PURPOSE
To compare pain response between two different flow rates (slow versus fast) of local anesthetic solution injected into palatal tissue using the recently available Wand Local Anesthetic System (WLAS), which provides the technologic advance to permit reliable replication of constant injection flow rates, regardless of tissue resistance.


METHODS AND MATERIALS
Twenty adult subjects received bilateral palatal injections of local anesthetic in random sequence during the same appointment following topical anesthesia application. Pain response was measured by subjective self-report using a visual analogue scale, a quantified verbal descriptor scale, and a comparison to prior injection experience, as well as an operator's global assessment of the subject's pain response. Heart rate, as a physiologic indicator of pain response, was also recorded.


RESULTS
All measurements of pain response were statistically less for the slow compared to the fast injection rate. No significant difference in mean heart rate, however, was demonstrated between the two flow rates. A slow, constant flow rate (161 sec/mL) of a 0.3 mL volume of local anesthetic solution was statistically less painful than a fast flow rate (29 sec/mL) during palatal injection. Contrary to the manufacturer's claim, the WLAS reduced but did not eliminate pain elicited by palatal injections in some patients.