Experimental studies of new topical anaesthetics on the oral mucosa

In order to reduce pain by injection, a frequently used topical anaesthetic is Xylocaine 5% ointment. This preparation, however, has certain limits in effectiveness. A new topical anaesthetic formulation, EMLA (Eutectic Mixture Local Anaesthetics), has been developed. Promising local anaesthetic properties on intact skin made it interesting to investigate the clinical usefulness of EMLA on mucous membranes and to find a suitable time of application. 30 volunteers, 20-40 yr, took part in the study. In two experimental double blind series, the topical anaesthetic effect was compared for EMLA 5% cream, Xylocaine 5% ointment, placebo cream, dry EMLA emulsion in cellulose discs and placebo discs. Application times were 2 and 5 minutes for the first three preparations, 2 minutes for the cellulose discs. The application areas were the alveolar mucosa in the lower buccal fold and the palatal mucosa. The pain by insertion of 27 or 30 gauge dental needles through the mucosa was registered. Xylocaine 5% and EMLA 5% reduced pain perception compared to placebo. For both Xylocaine 5% and EMLA 5% an application time of 2 minutes was found to be enough to produce a high degree of mucosal analgesia in the lower buccal fold. In the palatal area, however, the pain was not totally blocked by any of the investigated preparations but after 5 minutes of application EMLA showed a higher degree of analgesia. EMLA 5% creams was poorly localized at the applied area while the cellulose EMLA discs seemed to be more useful. No side effects were noticed.