9 Reasons Why You Can’t Get Numb At The Dentist

9 Reasons Why You Can’t Get Numb At The Dentist

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH🔬 Evidence Based
9 Reasons Why You Can’t Get Numb At The Dentist

If you’ve ever found yourself at the dentist’s office for a filling or crown and the novocaine isn’t working, does it mean the dentist is doing it wrong? If the dentist couldn’t numb your tooth, there may be some scientific reasons behind it! 

Simply adding sedation to your appointment won’t cut it. Your dentist needs to use novocaine or another local anesthetic to completely deaden your tooth to impair the nerve receptors; otherwise, you’ll still feel everything! But some people are more difficult to numb than others, or underlying factors may interfere with the local anesthetic medication’s ability to work correctly.

A "hot tooth" is a term dentists use to describe a tooth that is exceptionally difficult to numb due to heightened sensitivity or particularly painful tooth.

Why Is My Dentist Unable To Numb My Tooth?

So, the dentist couldn’t numb your tooth and decided to give you a lot more numbing medication until it started to kick in. Local anesthetic (the injectable numbing medicine) works by blocking the nerves in that area and preventing them from sending pain signals to your brain. Scientifically speaking, local anesthetics work by binding to sodium channels on the nerve endings, preventing the channels from opening and stopping the nerves from transmitting pain signals. Thankfully, it’s just temporary! Once your mouth is numb, it will only stay that way for a few hours before it starts to wear off.

Not Getting Numb At The Dentist

Without your dentist being able to get your teeth completely numb, they can’t work on your tooth to repair or reconstruct it. Sure, you can get your teeth cleaned, but anything where the nerve is stimulated— a dental procedure such as a filling or crown—is out of the question.

Some people may feel like their tooth is numb, but then halfway through the procedure they start to feel the sharp “zing,” that means the nerve is still sending signals. When that happens, your dentist will add more local anesthetic to numb the tooth. But like other types of medications, there’s a maximum amount of novocaine or lidocaine or other injectables that your dentist can safely administer. Which is why they want to get your tooth completely numb with the least novocaine as possible. 

But there’s some bad news to this. If you have a history of your dentist not getting you numb, it might not be the dentist’s fault. It could be some other issues going on that make you one of the few people that need more of or a different type of local anesthetic to deaden your tooth all the way. The good news is knowing that up front will help your dentist when it comes time to get you numb again!

Why Doesn't Novocaine Work On Some People?

“Novocaine” is sort of an outdated product. In fact, most dentists haven’t used novocaine in decades. Better numbing agents are available now, and today, most dentists use lidocaine. There are other types of “-caine” agents too, such as mepivicaine, bupivicaine, etc. None of that is really important to know, except that novocaine isn’t the only thing out there. 

Certain types of local anesthetics work better for certain types of people. For example, maybe you can’t have epinephrine (which is a really important ingredient for numbing agents to work.) If that’s the case, your dentist would pick a different type of local anesthetic and have to use a different dose.

If you know that novocaine or lidocaine doesn’t work on your teeth, let your dentist know. But just to rule out that it wasn’t a problem with your dentist’s technique, try to be as specific as possible or bring a copy of your previous dental records. 

Reasons The Dentist Can’t Numb Your Tooth

If your dentist couldn’t numb your tooth, it doesn’t mean that the novocaine isn’t working or they didn’t give you enough. Here are 9 different reasons why local anesthetic isn’t working during your dental appointment: 

1. Red Hair 

People with naturally red hair and fair skin don’t respond to numbing or sedation medications the same way that most people do. Some experts recommend that redheads need about 20% more numbing medication that people with other hair colors. 

People with red hair have a special gene that is responsible for both the color of their hair as well as pain responses. But fun fact, even though they might need more novocaine to get their mouth numb, redheads only require low doses of pain medications.

2. pH Imbalance 

The pH levels inside your novocaine, lidocaine, or other injectable dental anesthetic, can affect how quickly the medication works. The acidic pH is what makes it sting going in and depending on its acidity or neutrality, can sometimes delay how long it takes to become effective. Sometimes dentists will try a more normal blood ph or neutral pH anesthetic for various reasons, which works well for certain dental patients. Others say taking an antacid such as TUMS the night before their dental appointment also helps!

3. Infection

This one is probably one of the most common reasons why your dentist can’t get you numb. If you have a major infection, such as a severe tooth abscess, the pus and fluid around that space will make it extremely difficult for the anesthetic to work correctly. That’s one reason why a lot of dentists will prescribe an antibiotic leading up to your appointment; the medicine will reduce the severity of the infection and swelling, and your numbing medication will work more effectively. Just don’t make the mistake of cancelling your appointment because your tooth feels better after taking an antibiotic; the infection will come back if you don’t have it treated!

4. Previous Trauma Or Surgery

If you’ve had a major injury—such as an automobile accident or broken jaw—and required reconstructive surgery, your nerve tissues might be traumatized, scarred, or even displaced. In any of those scenarios, numbing the affected teeth could be challenging. 

5. Diabetes or Medical conditions

People with diabetes need to make sure they’re taking all of the proper medication before their dental appointment so that local anesthetic works correctly. Especially since so many numbing agents contain epinephrine and how local anesthetic can lower your blood glucose levels. 

6. Medications

Some types of medications can affect how local anesthetics work. The more common drugs known to interfere with novocaine are the ones that people take for high blood pressure. Your dentist will need to review your health history, even if you aren’t currently taking any medications, because of how certain numbing medications can affect things like your heart, for instance. And if you’re taking recreational drugs, it can make using local anesthetic dangerous altogether. 

7. Patient Anxiety

If you’re super anxious about dental treatment or have dentophobia, it can be harder to get your mouth numb. Some people believe that since high anxiety gets your cortisol and adrenaline pumping, it chemically interferes with how the local anesthetic works. This can make it harder or even impossible to numb your mouth or cause the novocaine to wear off more quickly.

8. Age

Most of us don’t build up a tolerance to numbing medication as we get older. In fact, age can make us more sensitive to things like sedatives and anesthesia. Since a lot of older individuals tend to take several different prescription drugs and tend to have a lower drug tolerance, dentists may want to rule out using novocaine and go with an alternative numbing agent during the appointment. 

9. Poor Injection Technique

Last but not least, you might not be getting numb because of how the local anesthetic is being injected. There are several different types of injections, locations, and techniques that dental providers have to learn during school. It’s not that they necessarily have to place the injection right where your tooth is. Instead, they might be targeting a main nerve in that portion of your mouth that will numb the entire area around the tooth being worked on. If they get it wrong, the medication won’t work correctly, and you won’t be numb. 

Talk With Your Dentist 

People who don’t get numb easily at the dentist’s office should always note this on their health history when visiting a new dentist. Trust me; your dentist wants to know! 

If you have concerns about whether or not the lidocaine or novocaine is going to numb your tooth good enough, your dentist will take things slowly and test your tooth as you go throughout the appointment. Most numbing agents take at least a good 5-10 minutes or more before your tooth is completely numb. From there, they can touch areas around your tooth to see if it’s completely “deadened” or not. Contact your dental office if you are concerned about your next next dental appointment.

Hot Tooth Recap 

Some people don’t respond to local anesthetics like novocaine very well, making it difficult for their dentist to get them numb during their procedure. If you know this up front, it can be extremely helpful to your dental team so that they can pick the best type of anesthetic to use (and no, it probably won’t be novocaine.) Even if it’s something obvious—like being a red head—share your past dental experiences so that your dentist can make sure you’re as comfortable as possible.

 Whitney DiFoggio MA, RDH
Written by Whitney DiFoggio MA, RDH"Teeth Talk Girl," is a registered dental hygienist. She started her dental health journey on YouTube, educating the public through videos.
Last updated onApril 1, 2024Here is our process

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