Begin the lesson by bringing in a few samples of nonprescription products for mouth pain. Let the students use a cotton swab to apply a small amount of the preparation to a quarter-sized area of the inner wrist. Ask how it feels. In groups, have the students read the labels on different preparations, write down the active ingredients, and try to find descriptions of those chemicals in reference books. Pain is an important safety feature of the human body because without it, no one would have any warning of injury.
Nerves transmit pain messages by a combination of chemistry and electricity.
Because nerves send messages by a combination of chemistry and electricity, interference in either area can relieve pain. The numbing effects of lidocaine last a while, too, which can be embarrassing. One nonchemical procedure, which dates back to the 18th century, avoids needles altogether by stimulating the tooth's nerve with electricity to numb it. Although it can't be used for everything, this electronic anesthesia has proven useful for some simple dental procedures. The patient controls the degree of stimulation by turning a knob on a small switch box.