A double-blind pilot study was conducted on 27 consenting human volunteers who had irreversible
pulpitis associated with persistent
toothache pain from open
carious lesions. Formulations tested contained either 0, 10%, or 20%
benzocaine and were identified only by a numbered code. Before the experiment started, a small amount of a known 5%
benzocaine gel was placed for 1 minute on the tongue of each patient to assure a sensation of
numbness within the oral cavity. Then the test tooth was washed with a gentle stream of warm water and dried with gauze. A randomly selected test medication was placed into the open cavity and around the gingival margins for 5 minutes. Pre- and posttreatment tests were conducted at the following timed intervals: 0, 5, 15, 30, 45, 60, 75 and 90 minutes. The tests included degree of
pain (rated: 0 = none, 1 = mild, 2 = moderate, 3 = severe); electrical pulp testing (EPT) by a modified, voltage-ramping instrument; and
ice water testing (0.5 mL directed quickly onto sound enamel of the tooth and rated: 0 to 4, with 4 being intolerable). After testing, or when
pain returned to baseline, endodontic procedures were performed. There was a significant increase (p < 0.032, Fisher exact test) in subjects obtaining
pain relief, rated by verbal descriptors, from the
benzocaine gels (14 out of 18 improved) compared to placebo (3 out of 9 improved). It was concluded that: 1)
benzocaine gels are effective formulations for temporary relief of
toothache pain, 2) there were no statistical differences in EPT scores between teeth having
pulpitis and control teeth, 3) there were no correlations between direction of EPT scores and
pain relief, 4) cold water testing was a good predictor of whether or not a tooth had
pulpitis, and 5) changes in cold water testing scores
after treatment could not be correlated to relief of
pain according to verbal descriptors. The effectiveness of
benzocaine in relieving
toothache pain verifies previous studies; however, a difference between 10% and 20%
benzocaine could not be demonstrated probably because of two factors: 1) the present experiment had a small sample size, and 2) there was no direct measurement of duration of
local anesthesia.