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Updated: Oct 27, 2022

Why anesthesia can cause the oral mucosa to balloon and how to avoid it.

The other day I was watching a movie that had an old-fashioned carnival scene in it. The main character was trying to win a prize for the girl of his dreams. The goal of the carnival game was to fill the fake clowns mouth up with enough water to blow a balloon up over its head. If he did it before the timer went off, he won!

Of course, my dental nerdy mind related that little carnival game with the experience of tissue ballooning up during certain injections. You’ve been there, right? You’re administering right into the mucobuccal fold, and the tissue starts to expand, like a balloon. At first glance it can be disturbing and then you start wondering if you did something wrong. Praying the balloon wont pop!

Okay…maybe I’m being a little dramatic, but there are reasons why this happens. Here are four reasons why the tissue at the mucobuccal fold begins to rise like a water balloon, and how to handle the situation.

Before I dive into the list, please note ballooning of tissue is very different than edema, which is a complication of delivering local anesthetics. Edema is a diffuse expansion of the tissue and is generally due to an allergic reaction.


If there is discoloration which is blue/purple in color, my first thought is the swelling is a hematoma. There are several reasons why hematomas occur. It could be caused by aggressive needle insertion, using a barbed needle or nicking a blood vessel. The way to avoid this from happening is to assure the mucosa is pulled tight and insert the needle slowly. Also, if you have used the needle a few times, the beveled edge of the needle could be barbed. A barbed needle is like using a fishhook in the patient’s mouth. It’s going to grab that tissue and shred it. Trust me, there are much better ways to catch patients than to fish for them. Change your needle if you’ve used it a couple of times or have contacted bone. We can’t always avoid blood vessels, but if you see a vessel near the area you want to inject, simply move a little to avoid the vascular space. Please make sure to aspirate regularly.

If a hematoma does occur apply pressure at once to stop the bleed. Also, the use of an ice pack can help reduce the swelling which accompanies this localized complication. Make sure you let your patient know they may have a bruise as well.


Quickly injecting the anesthetic solution can also cause the vestibule to puff up. With injections faster is not better. Even though our patients want us to hurry up and get the shot over with. Here’s the thing. It doesn’t make it better; it can make it so much worse. Not only does a quick deposition rate cause the tissue to distend, but it can also increase the likelihood of an anesthetic overdose. The solution to this problem is to slooooow down. Yep, take it down a notch. Ideally, it should take 2 minutes to administer an entire cartridge of anesthetic solution. But we all know that isn’t realistic. One minute per cartridge is safe and considered standard practice. In the end it makes everyone happy. You are in and out with that needle as quickly as possible, and your patient will be more comfortable (and safe).


If you are too close to the surface of the tissue, its possible the tissue could expand a bit more. The key is to make sure you are at the proper deposition site for the injection you are doing…which in general is at the apex or just a little past the apex of the tooth. If you do see tissue expansion, massage the anesthetic so it spreads into the rest of the tissue space.


When the mucosal tissue is thin, and the depth of the vestibule is shallow (like it is for the incisive injection) it is common to see an anesthetic bubble begin to form in that soft tissue fold. To prevent it from happening, slowly deposit the solution so it has time to disperse. If it continues, don’t fret. Go ahead and massage the injection site with mild to moderate finger pressure to disperse it into the remaining tissue and help it pass through the boney region.

If dentistry could always be fun like a carnival, our patients would be so much happier…as long as they aren’t the clown getting a mouth full of water.

Your take home message on how to avoid and treat that ballooning tissue is to have proper retraction, a fresh needle, slow down and gently massage the anesthetic in.

Implementing these strategies will help you care for your patients and help you Hit Your Best Shot!



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