Don’t Shock Me Bro!

As a dentist in private practice, I administer local anesthesia routinely. Or, in layman’s terms, I give numbing shots daily. That’s just two ways of saying the same thing!

Dental local anesthesia infiltration photo where no electric shock will occur

This type of injection is highly unlikely to give you an electric shock sensation

Occasionally, when I am doing certain injections (and note that there are different types of injections that dentists administer – more on that later), the patient will experience an electric shock sensation originating from the injection area. This ends up being quite a shock to the patient (pun intended) with me then subsequently spending significant time explaining why/what happened.

In addition to seeing this happen periodically in my own office, I get tons of comments and inquires on this blog about “the electric shock they got” from the dentist’s needle. Since nearly all of my articles are either about my own experiences – or from inquires I get on this blog – I decided it was time to do a post on this phenomenon.

Infiltrations versus Nerve Blocks

To understand why the electric shock occurs, a little background information is needed.

Femoral nerve block with an ultrasound

A nerve block guided by ultrasound being done by an Anesthesiologist.

In medicine – and I do consider dentistry to fall under the medical umbrella – there are various techniques for numbing a particular anatomical region. An infiltration is when local anesthetic is deposited directly adjacent to the site to be worked upon. In these cases, the local anesthetic works by affecting tiny, microscopic nerve endings that almost resemble a spider web.

In contrast, with a nerve block, the local anesthetic is deposited adjacent to a large branch of a nerve. This ends up numbing everything that the nerve supplies downstream from the area the anesthetic was administered.

To use an analogy: picture a tree. An infiltration is where anesthetic is placed next to a single leaf. A nerve block is when the anesthetic is placed next to a large branch close to where it is coming off the trunk.

Shock and Awe

When it does occur, the electric shock phenomenon is nearly always associated with a nerve block (as opposed to an infiltration). Why does this occur?

The shock sensation is believed to occur when the needle makes contact with part of the nerve trunk (sources: here, here, and here). The needle basically enters the tissue, touches the actual nerve, and the trauma from that immediate contact provokes a signal that your nervous system perceives and interprets as an electric shock feeling.

photo of needle and skull bone where you give a dental nerve block

In a mandibular nerve block, the needle is aimed right where a large nerve trunk (the inferior alveolar nerve) is about to enter the lower jaw (the mandible)

Some key facts:

  • The incidence of this occurring is between 1.3% to 8% of the time for mandibular nerve blocks (the large difference is based on different sample sizes).
  • Studies have shown that an electric shock sensation does not place the patient in a higher risk category for permanent nerve injury.
  • The most commonly involved nerve is the lingual nerve (which will give rise to a shock sensation in the tongue on the affected side.

As you can see, since the origin of the electric shock is contact with a nerve trunk, it is nearly impossible for this to occur with an infiltration.

What to Do if You Feel the Electric Shock?

With dentists administering millions of injections per year, this occurs on a regular basis throughout the world. Keep in mind:

bullseye showing that electric shock is due to hitting the nerve

An electric shock means your dentist hit a bullseye.

  1. Although the feeling was unpleasant and unexpected, the research clearly shows that this does not place you at a higher risk for permanent nerve issues (see bullet point #2 above).
  2. In many times, you get numb extremely quickly.
  3. This happens to all dentists periodically and this phenomenon alone does not mean your dentist is unqualified or negligent.

Since this occurs when the needle makes contact with the nerve trunk, it means your dentist was dead on with his/her aim. So, if you like, you can congratulate him/her on hitting a bulls-eye! Or, just understand that the human anatomy is unpredictable, and sometimes things like this happen.

Note: the sources used for this post are listed above and are also based on my own experiences. Note that I cannot answer emails to me asking for dental advice. The title for this post is based on the “Don’t Tase me Bro” incident and I have no relationship with Mr. Meyer. This post should not be construed as me providing commentary on that incident.

Comments

  1. Nicholas Akexander says:

    Dear Dr. Calcaterra,

    Thank you for your previous responses to my questions.

    The furthest tooth in back (next to where the wisdom tooth was) on the lower left side of my mouth is at times sensitive when I bight down, even when eating less hard food. The nerve in the tooth is activated as there is a crack in the tooth, according to my dentist.

    There are also months at a time when I don’t activate the tooth’s nerve when I chew where the tooth lies. It doesn’t bother me at all.

    I hesitate to place a cap on the tooth as eight or so years after placing a cap on the corresponding tooth on the other side of my mouth the tooth was so decayed under the cap that the tooth (what remained of it) needed to be pulled and replaced with an implant. The implant has over the past year involved numerous visits to the offices of two dentists and has so far cost me 6 or 7 thousand dollars. (We discussed this tooth in our exchange of posts last year.)

    What approaches should I consider with regard to treating the tooth in question? Am I taking an unreasonable risk of losing the tooth if I chose not to put a cap on it now?

    Thank,

    Nicholas

    • What you are describing appears to be what is called cracked tooth syndrome. This is difficult to diagnose but it sounds like the correct diagnosis based on your description. A crown may or may not fix the problem. The tooth may need a root canal too. I tell this to all my patients. This can’t be fixed with just a filling, because a filling will not prevent the crack from propagating more. If anything, a filling only would make the problem worse.
      Again, assuming a correct diagnosis, waiting will only make thing worse. The crack will only get deeper with time. A crack can get so deep that it gets onto the root surface, deep under the gums. At that point, the tooth is unrestorable. I have on many occasions had patients wait – despite my recommendations. They then come in acute pain. I open the tooth to do a root canal and the crack is incredibly deep on the root surface. We then have to extract it.
      I understand your frustration. But in this case, waiting can only make things worse, and you do run the risk of losing the tooth.

  2. This happened to me today, my dentist had trouble numbing a few of my upper teeth on a previous visit or two, so he injected me in a couple places for the furthest front upper bicuspid. No shock there, and it didn’t feel near as numb as the shot that hit the nerve for my entire lower left jaw. I felt a shock in every tooth on the lower left side of my mouth and the injection site is sore even 12 hours later.

    The left side of my lip is still a little tingly, and I’m hoping that clears up, but it’s not numb. I will say, when 8pm (5 hours after injection) rolled around and I could feel the upper half of my face, but my lower jaw was still stupid numb, I started to get scared. I bit my lip accidentally while talking before he started, and hadn’t eaten all day so I risked it and chewed extremely carefully a few hours after the appt, and trying to drink from only the right side of my mouth.

    around 6-7 hours from the injection I got some feeling back and I can feel most everything now but my lip and the inside of my cheek still tingle, although I do have feeling there again.

    I don’t think I’ve ever felt such physical numbness in my life, at least that I’ve been awake for, then again it’s been a long time since I’ve had any work done on my lower teeth.

    Feeling like all will be fine when the injection site stops stinging and being sore, and am about to take some ibuprofen to see if it helps. Not much of a religious person but I’m certianly thanking God that I’ve regained most of the feeling in my mouth even if it still feels weird 12 hours later… as the complete and utter numbness would just be one physical ailment too much for this beat up not even middle aged body.

  3. If this happens to you is it normal to be sore for a couple hours afterwards?

  4. Nichola Ryan says:

    I have had so much work done on my teeth and this has happened to me twice with the same dentist — I would not call her a good shot and I would never have her work on me again.

    • Denise Alter says:

      I’ve just returned from the dentist where I felt the shock, and it seemed as though it radiated from my jaw down my left side. It was very frightening, and I had a primal fear of “something is not right here”, along with not being able to move. I felt trapped. My dentist is very professional and caring, and explained what happened.

  5. I felt the “shock” sensation nearly two weeks ago, except it was more like an extreme metallic feeling than a true “shock.” The dentist was prepping to do “preventative” fillings on the two bottom teeth on the right side, directly in front of where my (long-ago extracted) wisdom tooth would be. My dentist explained she had hit the nerve, but I do not understand why she would have continued to inject there without adjusting it? (e.g. is it normal to inject directly into the nerve?!) She seemed very unconcerned but I was very sore for 2 days and a couple days after, the pain came back much worse. Now it feels far too similar to the upper tooth where her “handy work” filling placed the filling directly onto the tooth’s nerve and resulted in a root canal and crown. It not only hurts, but part of my jaw feels hot, despite constant ibuprofen and now antibiotics (three days so far).

    • Ted,

      What you appear to be describing is the shock sensation when the needle likely comes into very close contact with the nerve.

      The injection your dentist likely gave you is a challenging one to administer. The location of the nerve is variable so there is no way to know for sure where it is. In addition, the nerve is very small, much thinner than a piece of spaghetti. Perhaps slightly wider than a human hair. As a dentist, you don’t know if you “hit it” unless the patient reacts. As a dentist you try to get as close as possible without touching. If you don’t get close enough, then the patient does not get numb, and you have to reinject, which no one enjoys.

      Hopefully this clears up some confusion behind your recent experience.

  6. Absolutely felt this many many times, in fact today nerve was hit 3 times and didn’t get totally numb while finishing a crown. It doesn’t feel like a ‘sting’ either, I can handle all sorts of medical pain (kidney stones, childbirth, stomach surgery) but that nerve ‘shock’ takes the cake! I have had so much dental work from the time I was little to now, 42 and it has happened too often. I have to wonder if some of us are just unlucky and more sensitive to it as well.

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