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4 Things You Need to Know About Local Anesthesia

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Medically Reviewed By Colgate Global Scientific Communications

If you have a dental appointment coming up and you are expecting to have a small procedure to fix a problem, your dentist might need to numb part of your mouth using local anesthesia. If you’re new to having local anesthesia or you want some more information on what to expect, you’ve come to the right place. Read on for a simple guide on local anesthesia.

What Are the Types of Local Anesthesia?

There are two kinds of numbing injections your dentist could use during your appointment. The first is called a block injection. A block injection numbs an entire area of your mouth, like one side of your upper jaw. The second injection is called an infiltration injection, which numbs a smaller space. This type of injection only numbs the area near where they apply the dose.

You might be thinking about Novocain, a common name that comes to mind when thinking about local anesthetic drugs. But Novocain is not as widely used in dentistry anymore. Dentists have turned to other drugs that last longer and have better numbing effects than Novocain. Novocain is also more likely to cause allergic reactions, like swelling or interference with your central nervous system. The most common local anesthesia that dentists use is Lidocaine, but there are many others, all with names that end in “-cain”.

What Should I Expect When Given Local Anesthesia?

If you have an appointment coming up where you will be receiving local anesthesia, it’s good to know what to expect so you can address any concerns you might have with your dentist before your appointment.

First, your dentist will dry out part of your mouth with air or cotton. Next, many dentists will apply a numbing gel to the area where the injection will enter to reduce the initial pinch.

Then, your dentists will inject the local anesthetic around the tooth into the surrounding gum tissue. Because of the numbing gel, most people will feel nothing except for a slight sting as the anesthetic moves into the gum tissue. After the injection has numbed the area needed, your dentist will begin your treatment.

Depending on the type of anesthetic used and the method used to administer it, numbness can take several hours to wear off after leaving the dentist's office. Because of the continued numbness, you might find it difficult to speak clearly, eat or drink. It's best to take extra care while your mouth is still numb because you could bite down on the numb area and hurt yourself without realizing it. Make sure to ask your dentist how long you can expect to be numb after your appointment.

What are the Side Effects of Local Anesthesia?

Since local anesthetics are the most common drugs used in a dental office, they tested and understood very well. Because of this, side effects are very rare. However, there are a few things that could happen after injection.

One possible side effect is a blood-filled swelling called a hematoma, which might form when the injection needle hits a blood vessel. A hematoma might take a week or more to heal fully, just like a bruise on another part of your body would. While most hematomas will resolve on their own, it is always best to consult your dentist.

On rare occasions, the numbing medicine can cause numbness outside of the targeted area. If the numbness is extended and impacts other areas of your face, your eyelid, mouth or the impacted area could droop until the drug wears off.

Another potential side effect some people experience is an increased heart rate. However, this usually only lasts a minute or two. Make sure to tell your dentist or doctor before receiving a local anesthetic if this has ever happened to you.

Finally, a very rare side effect occurs when a needle inadvertently injures one of the surrounding nerves. If this happens, you could experience numbness and pains for several weeks and sometimes months. But there is good news! The nerve usually heals over time, so the pain should be temporary.

What Are Precautions to Take Before Receiving Local Anesthesia?

It is rare to have an allergic reaction to a local anesthetic but to avoid any potential issues, be sure to tell your dentist about all medicines you take, including over-the-counter drugs, herbs or vitamins. If you have had reactions to medication or local anesthesia in the past, tell your dentist, no matter how minor the reaction was. Some drugs can interact with local anesthetics, so it’s important to speak candidly with your dentist so he or she can take any necessary precautions.

Local anesthesia is very common in the dentist’s office and rarely leads to adverse side effects. The most important thing to remember is to always talk to your dentist about any allergies or concerns you might have before you receive the anesthetic. They can help ease your mind and make your procedure as pleasant as possible.


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This article is intended to promote understanding of and knowledge about general oral health topics. It is not intended to be a substitute for professional advice, diagnosis or treatment. Always seek the advice of your dentist or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.

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