Topical anesthetics are used in dentistry to reduce the initial soft tissue pain associated with local anesthetic administration and in management of gum pain associated in teething and other soft tissue irritation. Topical anesthetics are available in gel, liquid, ointment, patch and pressurized spray forms. When applying topical anesthetics to the soft tissue, especially in young children, use the smallest effective amount to avoid anesthetizing the pharyngeal tissues.
The most common topical anesthetics used in dentistry are those with benzocaine or lidocaine.
Ethyl aminobenzoate (benzocaine) is an ester local anesthetic. It is available in up to 20% concentrations. It is poorly absorbed into cardiovascular system. It remains at the site of application longer, providing a prolonged duration of action. Localized allergic reactions may occur following prolonged or repeated use and it is reported to inhibit the antibacterial action of sulfonamides.
Not known to produce systemic toxicity in adults, it can produce local allergic reactions. In April 2011 the Food and Drug Administration announced that “Topical benzocaine sprays, gels and liquids used as anesthesia during medical procedures and for analgesia from tooth and gum pain may cause methemoglobinenmia, a rare but serious and potentially fatal condition. Children younger than 2 years appear to be at particular risk. In the most severe cases, methemoglobinemia can result in death. Patients who develop methemoglobinemia may experience signs and symptoms such as pale, gray or blue colored skin, lips and nail beds; headache; lightheadedness; shortness of breath; fatigue; and rapid heart rate.”6
Most of the cases reported were in children younger than 2 years who were treated with topical benzocaine gels for the relief of teeth pain. The signs and symptoms can occur after a single application or multiple applications and can begin within minutes and hours of application.
Topical anesthetic manufacturers, i.e., Orajel, has removed benzocaine as its active ingredient and substituted oil of cloves.
Lidocaine is absorbed by the soft tissue and can enter the cardiovascular system. Therefore, when using topical lidocaine in conjunction with injectable lidocaine, the clinician must calculate the additive amount administered, especially in a small child, to avoid anesthetic toxicity.