An analysis of the effectiveness of two topical anesthetics.

This study compared the effectiveness of topical benzocaine 20%, lidocaine 5%, and a placebo in reducing the pain caused by needle insertion when the medicament was placed in the mucobuccal fold above the maxillary canine eminence. Both topical anesthetics and the placebo were randomly tested against each other bilaterally. For uniformity the agents were left in place for three minutes before needle insertion. A 27 gauge short needle mounted on an aspirating syringe was then inserted just past the bevel. Each subject rated the degree of pain on a visual analogue scale 100 mm in length. A pulse oximeter was used to record the heart rate. The results indicate that both topical anesthetics are significantly better than the placebo in reducing pain caused by needle insertion, although no statistically significant differences were found between the two topical anesthetics. Statistically significant differences in heart rate were seen, but these differences were not clinically significant. It is concluded that benzocaine 20% and lidocaine 5% significantly reduce the pain during needle insertion.