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Novacaine

 

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Overview
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. When a nerve receives a pain stimulus over a certain intensity, it "fires" by changing the arrangement of positive and negative charges across its cell membrane. When the message reaches the end of the nerve cell, chemicals known as neurotransmitters spill out into a space (synapse) and stimulate the receiving areas (receptors) on the next nerve cell. The signal passes from nerve to nerve very quickly until it reaches the brain, where the message registers as pain (and you say "Ouch!"). Because nerves send messages by a combination of chemistry and electricity, interference in either area can relieve pain. Traditionally, dentists have used a shot of lidocaine (a substitute for Novocain) to numb the tooth so the patient can't feel the drill. This is a little alarming in itself when the cavity is in a lower jaw tooth; the only available nerve to numb is way in the back of the mouth, so the needle is several inches long. The numbing effects of lidocaine last a while, too, which can be embarrassing. Ever try to talk when your mouth is numb? 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. There are generally two electrodes, placed inside or outside the mouth (sometimes one in and one out). The patient controls the degree of stimulation by turning a knob on a small switch box. When the stimulation is turned off, the numbness goes away immediately. Anesthesia works in a number of ways. Some anesthetic drugs block certain receptors. Others inhibit biochemicals that increase the nerve's likelihood of firing. Scientists disagree on how electrical stimulation works, although some think it somehow results in the release of natural painkilling substances in the brain called "endorphins."

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