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Why Your Dentist Can’t Get You Numb

Dentist Getting Patient NumbDid you know that over four million dental injections are given every year in the United States?  The failure rate is estimated to be anywhere from 5 to 15%.  that means that there are anywhere from 200,000 to 600,000 dental injections that don't get the patient numb.  That means that people get poked by their dentist with a needle and don't end up getting numb about every minute.

It's no wonder that a lot of people come into my dental school and tell me something similar to, "My dentist has trouble getting me numb -  I usually need a lot of novocaine in order to get numb."  As a side note, we normally use lidocaine, not novocaine as many patients believe.

So why do so many dental anesthetic injections not work - why can't your dentist get you numb?

Seven Reasons Why Your Dentist Can't Get You Numb

An article published in the January 1991 issue of the Journal of the American Dental Association sheds some insight into this issue by giving five reasons why dental injections sometimes don't work.  I also found a couple of others and added them onto the list below.

1 - Anatomic Variations

Everyone is different.  Some people's jaw flares out wider than others, making it hard to visualize where that person's nerve is.  Some people have a longer jaw or extra muscle and/or fat around their jaw. In patients that are missing lots of teeth in the back of their mouth, it's harder to visualize where the nerve is.  Also, young patients can have different anatomy depending on their stage of growth, making it hard to get the anesthetic in the right spot.

2 - Technical Errors by the Dentist

Dentists aren't perfect!  Sometimes we can put the needle in the wrong place and give the anesthetic too low, too high, or too far to the side.  Also, we might not put the needle in deep enough, or we may accdentally deposit the anesthetic in a blood vessel, which is why your heart can beat fast when getting a dental injection.

3 - Anxious Patients

Some anxious patients may think that they aren't numb and jerk away in fear when we start to drill.  In cases like this, I usually tap around their gums on the numb side and then on the side that isn't numb to let them feel the difference and realize that they really are numb.

4 - Inflammation or Infection

When people have swelling in an area, it can be harder to get them numb.  One theory says that the acidic tissue makes it harder for the anesthetic to take effect.  Antoher theory says that since the patient has been in pain for so long, they have an increased sensitivity to pain which makes it harder for them to get numb.

5 - Defective Anesthetic Solutions

I haven't had experience with this one, since my dental school has a pretty good quality control program to ensure that the dental anesthetic stays potent.  However, sometimes a dentist may use dental anesthetic that has expired or was improperly stored or manufactured.  This made me realize that I should always go with a respected brand name of dental anesthetic and not get the cheaper stuff to save money.  There's no point in cutting corners if it will inconvenience my patients.

6 - Having Red Hair

People with red hair have more difficulty succumbing to the numbing effects of dental anesthetic.  They also have a greater fear of the dentist.

This article published in the July 2009 Journal of the American Dental Association states, "People with naturally red hair are resistant to subcutaneous local anesthetics and, therefore, may experience increased anxiety regarding dental care."

7 - Having Joint Hypermobility

Those who suffer from Ehlers-Danlos Syndrome can be insensitive to local anesthetics used in dentistry.  You can check out this article for more information on local anesthetic failure in those with joint hypermobility.


If your dentist can't get you numb, more than likely there is a specific reason.  In my experience, I've found that there are many people who have slightly different anatomy in their jaws which makes it harder to position the needle so that the anesthetic gets deposited where their nerve is located.

Do you have any questions, questions, comments, or concerns about getting numb at the dentist?  If so, feel free to go ahead and leave a comment below.  Thanks for reading!

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15 Comments |  Leave A Comment

  1. This is a very informative blog! I feel that it is very important to inform your patient of everything going on and why certain proccrdures or medications may or may not be effective. By helping them to understand it alleviates their fears because they understand what is going on.

    • Thanks for your comment, Dr. Barkhordar. I agree!

    • Today I had a tooth that needed pulling. After 5 or 6 injections of novacaine and an hour of excruciating pain the dentist gave up and sent me to an oral surgeon. Due to the nitrous i couldn't tell you how many injections he gave me, but he ended up drilling into my tooth and giving me an injection thru the root directly into the nerve... Holy cr*p, it was like an electric shock, and it still didn't get numb. Pulled it anyway. Sheesh, at least the gas helped...

      he told me as I was leaving that I was a mystry to him!

      Any ideas?


  2. I need a lot of work done because I had mercury fillings which cracked because they are very old and I grind my teeth at night. I went to a dentist in Atlanta.Cleveland Ave. She gave me lidacaine instead of novocaine anyway I was in pain the entire time she removed my tooth and the chips. then she gave me water to rinse my mouth.the water was brown. I asked what is in the water. she said that is the way it comes out of the pipe. I saw her child in the other room and her husband at the desk up front. I asked if this is the water you give your family. she said she has some bottled water and asked if I wanted one. I paid that dentist 200.00 cash to treat me on that dreadful Saturday. I had to ask for a prescription for pain medication and I had to ask if I needed an antibiotic for any infection. she did not want to but finally gave me a pain medication prescription. I asked her how long she had been in business and she told me she had been in business a long time and has awards for her work. I do not see how that could be true. I would never send anyone, not even someone I did not get along with to that woman.

  3. does getting an injection in your mouth hurt?

  4. I've been seeing my current dentist for several years and he has done two crowns and a filling or two with no problem. Recently he's twice been unable to get one of my lower tooths numb. We waited 3 weeks after the first attemp, and second attempt went the same. My tongue would go numb, but my lip and tooth would not. In fact, the tooth actually seemed hypersensitive after the two shots. Touching the tooth with a dental pick made me alost jump out of the chair. The dentist sent mme home and about two hours later my lip finally went numb (like it norally does in the dentist's office after the shot). The numbness lasted maybe 30-40 minutes...then went back to normal.

    Is there anything I can tell my dentist that might help me get me numb next time? He's a great dentist and I know "it's me" not "him". This work, btw, is to replace an existing, old, filling....which tells me that at least at some point, some dentist years ago was able to get that tooth numb.

  5. how can i make my dentist understand that my lower right back tooth WILL NOT geet numb my last dentist who was wonderful by the way tried three times but no luck i've had other extractions and there was no problem ....... my last dentist tried amoxicillian and ciproflaxin but no luck, then i stoped going to her because i moved and my new dentist didnt listen to my complications in the past with these two teeth when i told her she was like that was probaly becase you had an infection dont worry u dont have onr now there shouldnt be any problem .......but ther was and when i complained about the exscruiating pain she snaped at me that it wasnt pain just pressure .. um i know the difference between pain and presure i hae had several extractions before so the pain went on and i was only able to get out one tooth that day and on my way out she says"WELL AT LEAST YOU KNOW WHAT TO EXSPECT NEXT TIME" what should i do i dont have insurance and this is the only program that is literally free her in sanantonio im happy to get the free treatment but the pain was just horriable .

  6. You think you've got problems with your dentists; at least you can communicate with them.
    I live in mainland China and dental treatment here is awful, really awful. Today after a few days of intense toothache I gave in and decided to go to a local dentist. One of the big problems in China is that many people are against western medicine because (they say) it damages the body. The upshot of this is that (I believe) their lidocaine sits around for a long time in high temperatures and maybe past it's sell-by-date. Then an unsuspecting foreigners turn up for treatment and asks for an injection of bad lidocaine.
    I myself have always had a problem with my nerves not getting numb prior to drilling and this occasion was no different. Even after four shots I could still feel pretty bad pain. Now if you add to this the fact that dental practices here are very bizarre in as much that they drill your tooth, then insert cotton wool with some kind of Chinese medicine on it and tell you to go away until tomorrow. What this means is that you have a big hole in your tooth with exposed nerves and a big lump of cotton wool. Imagine the problems this creates in trying to drink or eat, and this can go on for several days. I am sure my little story has put your problems into context!
    Incidentally I am a UK man who teaches English here.

  7. Hi,

    I am resistant to numbing for some reason. I've found a local dentist however who is AMAZING, truly pain-free. First he uses a q-tip and numbs the area where the injection is about to go. The injection is barely felt, and then a 2nd injection usually follows in my case, a few moments later. THEN, he gives me a "booster", which after all these visits, has finally told me that he's actually drilling into the bone a bit, and making an injection straight into the bone. It turns the side of my mouth into a block of wood, and I feel practically nothing that is going on in my mouth while he's working.

    He said most dentists will not do this procedure though, even though he has had several sessions where he teaches other dentists the technique.

    Why isn't this "booster" done more often? It is truly the best thing that has happened to me, with regards to my dental care.

    • Hi Michael - I do sometimes use a similar injection where I numb the patient around the tooth to be worked on and then inject into the ligament between the tooth and the bone, which allows the anesthetic to diffuse directly into the bone.

      I think many dentists (myself included) are hesitant to drill into someones bone simply to get them numb, which I believe explains why more dentists aren't doing that type of injection.

      Like any injection we give, there are some risks to this injection that goes in your bone. Here's a quote from a study that discusses this type of injection:

      "The risks factors associated with intraosseous injections include separation of the perforator needle from the plastic shank and that localized infection can occur at the site of perforation and may require use of oral antibiotics. The most significant concern with this route is increased heart rate that occurs when using epinephrine and levonordefrin containing solutions."

      Thanks for the question - Sounds like a good post idea someday!

      • Wow, thanks for the great response!

        Your reply was interesting to me, "simply to get them numb". I am definitely looking for your feedback here, trying to understand- wouldn't numbing the patient be high priority when doing work in their mouth?

        My first dental experiences as a child with military dentists were not great, and when I had to have a wisdom tooth pulled in my 20's (about 20 years ago) it was a brutal, painful affair. In this day and age I would say barbaric even. It was about a year later when another tooth had to go, that I found the current guy.

        My dad has neglected at least 10 years of dental care, simply because he dreads the pain and discomfort of dental work.

        Is there a level of pain in the patient's part that is considered acceptable by dentists?

        • Hi Michael - I probably wasn't very clear with my last post. Numbing a patient is an extremely high priority. In fact, I always want my patient to be comfortable and will not work on them unless they are.

          In response to your question, there isn't a level of pain on the patient's part that is considered acceptable to me. If I sense that the patient can feel something, I ask them and then let them know that I'd like to give them some more anesthetic so that they are comfortable. Using the standard dental injections, I am usually successful at getting patients numb. When that fails, I will usually go to the injection in the ligament, which gets the remainder of the patients numb. That injection is basically an injection into the bone, without having to drill directly into the bone.

          With the injection techniques I'm using, I am able to get my patients numb and so I haven't felt the need to learn the technique where I would drill into the bone just to get a patient numb. Bear in mind that many dentists only do standard injections and do not have the equipment to do an injection into the ligament around the tooth. This may be where your bad experiences have come from.

          Ask your dentist if he's willing to give you a PDL injection in your ligament next time and see if that works just as well as the injection where he has to drill into your bone. Both injections deposit the anesthetic into the bone around the tooth. Both can cause some residual pain after the numbing wears off. But only one of them involves directly drilling into your bone.

          Unfortunately there are dentists out there who don't place a high priority on patient comfort. I think most of us do try to make sure that our patients are as comfortable as possible when working on them.

          Let me know if you have any other questions. Thanks for your insightful comment!

  8. I am on a seizure medication where it is literally eating my enamel and causing me to get cavities even though I brush twice daily and take great care of my teeth. ( This is my first time ever having any major work done on my teeth.)

    Recently I had to have fillings. The first time I had 2 fillings and a wisdom tooth pulled which took 5 injections and I was numb for 6 hours. The second time I had 2 more fillings and the first injection didn't numb me and my dentist stuck me 3 more times and I was numb for 4 hours. The last time that I went ( today) he stuck me twice and waited 15 minutes and I wasn't numb, then he came back and had 2 different vials one yellow and one blue and I was stuck 9 more times and I still wasn't numb. The pain was very unbearable and I had to more or less bare the pain and he drilled 3 of my teeth and I am due next week for a filling and a crown. After I left the dental office my toungue was completely numb on one side and a small part of my bottom lip was too. It lasted about 20 - 30 minutes.

    Is there a reason why I am not really getting numb and is there something that I could let my dentist know or having him try to make this a lot easier on me. I am literally petrified to go back for the rest of my dental work due to the pain. Not to mention I was referred to an Oral Surgeon to have 3 wisdom teeth extracted.

    • Hi Kayla - I would tell your dentist your concerns. There are other injections that can be done that will get individual teeth numb. You could ask your dentist to do a PDL injection (where the anesthetic is placed directly into the Periodontal Ligament right around the tooth and gets it numb). I'm sure your dentist doesn't want you to be uncomfortable and will help you find a good solution. Good luck!

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Tom, Creator of Oral AnswersHi, I'm Tom. I recently graduated from dental school and am now a dentist in Bridgewater, Virginia. I started this blog to help people take better care of their teeth. You can learn more about me or ask me a question.

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