|Topical Anesthetics in the Dental Office|
Topical anesthetics are applied directly on the skin or inside the mouth. Dentists use them to relieve pain caused by dental injections and procedures. You also can buy topical anesthetics in grocery and drug stores. These products contain drugs such as benzocaine, lidocaine or tetracaine. People use them to ease pain from teething, braces, canker sores or toothache. They also can relieve pain or itching outside the mouth.
Dentists use topical anesthetics for several purposes:
- To prevent or reduce the pain caused by a numbing shot
- To prevent people from gagging. The "gag reflex" may occur during an X-ray or when a tray is placed in the mouth to take an impression or give a fluoride treatment.
- To decrease discomfort during scaling and root planing or the removal of stitches
- To relieve pain from dry socket. This problem sometimes occurs after tooth extraction.
Topical anesthetics are applied in several ways:
- Adhesive patch
Some topical anesthetics have flavors, such as fruit, mint or bubble gum.
Most topical anesthetics are the same drugs as local anesthetics that you get in a shot. But topical anesthetics usually are stronger. That's because not all of the drug will work its way through the tissue.
Before giving you a topical anesthetic, your dentist will review your medical and dental history. One reason is to see if you have any history of allergic reaction. People can have a reaction to the anesthetic or to other ingredients, such as flavorings and preservatives.
Before numbing an area, your dentist will dry it with a gauze pad. Then an applicator (usually a cotton swab) is used to hold the anesthetic on the area for two to three minutes. Topical anesthetics also can be applied in the form of a spray or an adhesive patch.
Topical anesthetics numb the nerves 2 to 3 millimeters below the surface. They usually are effective for 15 to 30 minutes. That's enough time for you to receive a shot or have stitches removed.
Many of the anesthetics used in the dental office also are found in over-the-counter products. These include gels to relieve mouth pain and sprays to relieve sunburn or a sore throat. Over-the-counter products are not as strong as those used in the dentist's office.
Here are some common topical anesthetics.
Lidocaine comes in an ointment and a patch. It commonly is used to reduce pain when you get a shot. Viscous lidocaine is a thick liquid form. It can be used to relieve pain from dry socket. Some people have this problem after a tooth extraction.
After lidocaine is applied, the area gets numb in about 3 minutes. The numbness lasts about 15 minutes. Lidocaine is approved for in-office use only in the mouth. Over-the-counter products that contain lidocaine should not be used in the mouth. These products include ointments to treat cold sores.
The patch is a small adhesive strip that contains lidocaine. It is placed in the mouth for up to 15 minutes. The area usually gets numb in 2 to 5 minutes. The effect lasts for about 30 minutes after the patch is removed.
| Anesthetic patch in use
The patch works at least as well as lidocaine ointment. It's also somewhat safer because less of the anesthetic enters the bloodstream. The blood level is about half of that produced by applying lidocaine ointment. It's just over one-tenth of what you get from a typical shot.
Benzocaine is available in ointments or liquids. They contain from 7.5% to 20% anesthetic. Bezocaine is used to reduce the pain of injections. It works in much the same way as lidocaine. It is also the only topical anesthetic sold over the counter for mouth pain. These products are used to relieve pain and discomfort from toothache, canker sores, braces, teething and dentures.
Tetracaine is a powerful topical anesthetic. It dissolves in water. For this reason, it spreads through the body faster than other anesthetics do. Tetracaine is used with benzocaine to reduce the gag reflex before taking impressions or X-rays. Numbness occurs very rapidly (within 1 minute). It lasts for about 15 minutes. This two-drug anesthetic is applied in the form of a spray. Tetracaine easily enters the bloodstream. Therefore, it must be used cautiously. Overdoses can lead to severe reactions, including death.
This compound is used in many over-the-counter lozenges for relieving sore throat pain. It also is used in the dental office, most commonly in liquid form. Dyclonine hydrochloride takes up to 10 minutes to produce numbness. However, it can be used in people who are allergic to other topical anesthetics.
EMLA (eutectic mixture of local anesthetics) is a combination of lidocaine and prilocaine. Generally, it is given in liquid form. Until recently, EMLA was approved only for numbing intact skin. It was not used inside the mouth. This is because EMLA reaches the bloodstream rapidly if applied in the mouth.
In 2004, the U.S. Food and Drug Administration (FDA) approved an EMLA product called Oraqix. Oraqix is a gel that can be inserted into the space between the teeth and gums. The gel numbs the gums within 30 seconds. The effect lasts for about 20 minutes. It is only designed to numb soft tissue. It will not numb teeth. For this reason, Oraqix may be useful during deep cleaning procedures such as scaling and root planing. Scaling and root planing involves cleaning the teeth above and below the gum line and smoothing the surfaces of the teeth.
Topical anesthetics used in the mouth have not been shown to affect developing infants. They also don't show up at significant levels in breast milk. If you are pregnant or nursing and you are concerned about topical anesthetics, ask your dentist.
Topical anesthetics have some limitations:
- They can be toxic if applied across a large area, This is particularly a danger for tetracaine, because it is so easily absorbed. In January 2009, the FDA issued a health advisory to remind consumers and health care providers that improper use of topical anesthetics can cause serious side effects. The FDA advised against using these products over large areas of skin, or covering the area after they are applied. The warning followed several reports of serious problems when topical anesthetics were used for laser hair removal.
- Some people are allergic to the drugs, flavorings or other ingredients.
- Most topical anesthetics have not been tested in very young children (under 1 to 2 years of age) or the elderly.
The risk of receiving a topical anesthetic is usually quite low. However, risks include:
These are rare and usually mild, but severe reactions have been reported. A mild allergic reaction can include swelling and raised welts on the skin that can itch or burn. Some allergic reactions occur up to two days after the anesthetic is given.
Toxicity resulting from too much anesthetic
Symptoms can include:
- Blurry vision
- Unusual nervousness or restlessness
- Dizziness or lightheadedness
- Ringing or buzzing in the ears
- Difficulty breathing
- Seizures (with a more severe reaction)
- Irregular heartbeat
Excess amounts of benzocaine have caused methemoglobinemia. In this condition, hemoglobin (a substance in red blood cells) is converted to an inactive form. It can't do its job of carrying oxygen through the body. Mild forms of this condition may not produce any symptoms. More severe cases can cause fatigue, a bluish or grayish cast to the skin and difficulty breathing. This is a relatively uncommon condition. It has occurred primarily in three situations:
- In the operating room where doctors have applied too much benzocaine or tetracaine plus benzocaine to the back of the throat. This is done before placing a tube for breathing or for viewing the stomach or heart. Methemoglobinemia is far more likely to occur in this situation in elderly, weak patients.
- In teething infants, if parents have ignored dosing directions and applied too much benzocaine liquid or gel throughout the entire mouth
- In young children who have accidentally swallowed toxic amounts of benzocaine
For mild cases of methemoglobinemia, the person usually just needs to be observed closely. In more severe cases, methylene blue dye is injected into a vein. This acts as an antidote.
To prevent these problems, follow the instructions on the drug's package. Keep all medicines out of the reach of young children.