Topical anesthetic efficacy on palatal mucosa after pretreatment with microneedles

Objectives: This research evaluated whether efficacy of topical anesthesia increases on palatal mucosa after pretreatment with microneedles (MNs).
Methods: In this crossover, randomized, double-blinded study, 30 male volunteers were submitted to topical application of MNs or flat patches (negative control) on palatal mucosa, bilaterally in the canine region, which was followed by topical application of EMLA®, a eutectic mixture of lidocaine and prilocaine for 2 or 5 minutes. Immediately after, an infiltrative anesthesia was performed by using a 30-gauge short needle and 0.3 mL of 2% lidocaine with epinephrine 1:100,000. Pain sensation during needle insertion and liquid injection was evaluated by using a visual analogical scale (VAS). VAS (in mm) results were submitted to the Mann-Whitney test (α = 5%).
Results: Pain values (in median(max-min)) for needle puncture and solution injection, respectively, after a 2-min application of EMLA were 11(72-0) and 10(81-0) after MN pretreatment, and 16(86-0) and 11(63-0) after flat patch pretreatment. After 5-min application of EMLA the needle puncture and solution injection pain values were 4 (56-0) and 4 (50-0) after MN pretreatment and 10 (52-0) and 5 (84-0) after flat patch pretreatment. There was no reduction in pain during needle insertion and liquid injection from use of MNs pretreatment after 2 or 5 min application of EMLA (p>0.05).
Conclusions: Microneedle treatment of palatal mucosa was unable to increase topical anesthetic efficacy of EMLA® in reducing pain during needle puncture or solution injection. This suggests that additional approaches of directly delivering the anesthesia deeper into the mucosa are required, and coated microneedle maybe a better approach.