Dental procedures often require numbing the mouth to ensure patient comfort and allow for effective treatment. This process, known as local anesthesia, is a routine part of many dental visits, from simple fillings to more complex extractions.
The Science of Numbing: How it Works
Local anesthetics function by temporarily blocking the signals that nerves send to the brain. Nerves transmit sensations, including pain, through electrical impulses. These impulses are generated by the movement of sodium ions across nerve cell membranes. The numbing medication interferes with this process by binding to specific channels on the nerve fibers, preventing the influx of sodium ions.
When sodium ion movement is inhibited, the nerve cannot generate or transmit electrical signals. This interruption means that pain sensations from the treated area never reach the brain. The medication primarily targets sensory nerves, which are responsible for feeling, while largely leaving motor function intact. As the anesthetic is gradually broken down and eliminated by the body, nerve function returns to normal.
Common Numbing Medications
Dentists utilize several types of local anesthetic medications, each with distinct properties regarding onset and duration. These drugs are generally classified as amide-type anesthetics, and include Lidocaine, Articaine, Mepivacaine, and Bupivacaine.
Lidocaine is a widely used local anesthetic. It typically begins working within minutes and provides numbness for one to three hours, with effects lasting longer when combined with a vasoconstrictor.
Articaine is another common choice, recognized for its high lipid solubility, which allows it to penetrate tissues effectively. It often has a fast onset, around one to nine minutes, and can provide profound anesthesia.
Mepivacaine has been used in dentistry since the 1960s and is available with or without a vasoconstrictor, making it a suitable option for patients who may not tolerate vasoconstrictors well, such as those with certain medical conditions. Its onset is generally fast, and its duration is intermediate.
Bupivacaine provides longer numbness, often up to 8 to 10 hours, beneficial for procedures that might cause significant post-operative pain. It has a slower onset compared to Lidocaine but its prolonged effect can reduce the need for strong pain relievers after a procedure.
Many of these anesthetics are combined with vasoconstrictors, like epinephrine (also known as adrenaline), which constrict blood vessels. This constriction keeps the anesthetic localized in the treated area, prolonging its numbing effect, reducing bleeding, and slowing its absorption into the bloodstream, thereby decreasing systemic toxicity.
How Numbing is Administered
Administering dental numbing medication typically involves a few steps. Initially, a topical anesthetic, often in gel or spray form, may be applied to the surface of the gum tissue. This topical application numbs the injection site, making the subsequent injection more comfortable. Many dentists apply this topical agent for several minutes to allow it to take effect before proceeding.
After the topical anesthetic has had time to work, the dentist will use a fine needle to inject the local anesthetic solution. There are two primary injection techniques: local infiltration and nerve blocks. Local infiltration involves injecting the anesthetic directly into the tissue around the specific tooth or area being treated, numbing a smaller, localized region. Nerve blocks, conversely, are used to numb a larger area by injecting the anesthetic near a main nerve pathway, which then numbs all the tissues supplied by that nerve. Dentists employ careful techniques, such as slow injection, to minimize any discomfort during the administration of the anesthetic.
What to Expect During and After Numbing
Once the local anesthetic is administered, a patient will typically notice the area becoming numb within a few minutes. This sensation might manifest as tingling, heaviness, or a complete loss of feeling in the affected region (e.g., tongue, lips, or cheek), depending on the injection site. It is common for the soft tissues, like the lips and tongue, to remain numb longer than the actual tooth. For example, tooth numbness usually lasts 2-3 hours, while lip and tongue numbness can persist for 3-5 hours. The overall duration of numbness can vary, ranging from one to several hours depending on the type and amount of anesthetic used, the injection site, and individual metabolism.
As the numbing effect begins to wear off, a tingling sensation often returns as feeling gradually restores. During numbness, be cautious to avoid accidentally biting the lip, cheek, or tongue, as these tissues cannot be felt. Dentists advise against eating or drinking hot liquids until sensation returns to prevent accidental injury. Staying hydrated can help the body process and eliminate the anesthetic. If numbness persists for an unusually long time (beyond 4-5 hours for a routine procedure) or is accompanied by pain or swelling, it is advisable to contact the dentist.