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For some dental procedures, your dentist will numb a part of your mouth by injecting anesthetic drugs into your gum or inner cheek. This procedure, called local anesthesia, numbs only the area near the injection.
The most common local anesthetic used in dental offices is lidocaine. Others include prilocaine, mepivacaine, bupivacaine and other drugs with names ending in "-caine." The newest local anesthetic released in the United States is articaine. Procaine, the first synthetic anesthetic, which most people know as Novocaine, is no longer used in dentistry because newer anesthetic drugs last longer, are more effective and are less likely to cause allergic reactions.
The solution your dentist injects contains more than just an anesthetic. It may also include:
- A vasoconstrictor, such as epinephrine, which narrows your blood vessels and helps the anesthetic's effect last longer
- An antioxidant (which contains sulfites or methylparabens) to prevent breakdown of the vasoconstrictor
- Sodium hydroxide, which chemically adjusts the acidity (pH) of the anesthetic solution to help it work properly
- Sodium chloride, which helps the solution enter the bloodstream
Two types of local anesthesia injections are possible, depending on where and how your dentist inserts the syringe. A block injection numbs an entire region of your mouth, such as one side of the lower jaw. An infiltration injection numbs a smaller area. In each case, the numbness will last from one to several hours and may give you that "fat lip" feeling after you leave the dentist's office.
If you need local anesthesia, your dentist will dry the part of your mouth where the injection will go by using a cotton swab or by blowing air on the area. Many dentists then swab the area with an anesthetic gel to numb the injection site.
Your dentist will slowly inject the anesthetic. The needle can sting. However, most people don't feel the needle itself. Instead, the sting they feel is caused by the anesthetic moving into the tissue.
After you leave the dentist's office, you may find it difficult to speak clearly or eat, and drinking from a straw can be messy. Be careful not to bite your mouth or lip while the area is still numb because you could cause significant damage without realizing it.
Side Effects
Local anesthetics are the most common drugs used in the dental office. Side effects are very rare.
One possible side effect is a hematoma, or blood-filled swelling, that can form when the needle hits a blood vessel. The anesthetic sometimes causes numbness outside of the targeted area, and your eyelid or mouth can droop, but these effects disappear when the anesthesia wears off. Sometimes, a medicine included in the injection — a vasoconstricter to narrow blood vessels — can cause your heart to beat faster. If this happens, the effect lasts only a minute or two. The needle can injure a nerve, causing numbness and pain after the anesthesia wears off. The nerve usually heals over time, and the symptoms disappear.
Concerns
Although allergic reactions to local anesthetics are rare, your dentist may ask about any allergies you have had.
Because certain drugs can interact with local anesthetic solutions, tell your dentist about all medications — both prescription and over-the-counter — you are taking.
©2002-2005 Aetna, Inc. All rights reserved.
Reviewed by the faculty of Columbia University College of Dental Medicine
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