Why It Can Hurt to Open Your Mouth After a Filling

Every now and then, we get a phone call from a patient who we saw a couple of days earlier. It goes something like this:

I had a filling done on my last tooth on the lower left three days ago. The filling and tooth feel fine, but it hurts to open my mouth, especially if I try to open wide.

We then go on to explain to our patient WHY this is the case and how it is normal.

So why is there pain with opening? There are two major factors.

Dental Injections for Lower Molars

In many cases, the pain while opening is from the injection. For lower molars, most dentists will do a nerve block, which involves a very long needle. See the photo below.

Dental shot for a lower tooth can cause pain while opening

A dental injection used to anesthetize a lower right molar. The needle in this photo is 1 and 1/4 inches long.

As can be seen in the above photo, a needle is inserted into the muscle in the back of the mouth. In most cases, for this injection, the needle goes in nearly to the hub, which would mean approximately 1 and 1/4 inches.

Here’s an analogy: feel your biceps and press it hard enough so you can feel the bone underneath. Then, imagine taking a needle, and inserting it through the biceps, approximately 1 inch, until the needle hits bone. Then, imagine doing that a second time. Don’t you think that moving the arm and using that muscle over the next several days would hurt?

The biceps analogy is very effective. Everyone understands that their arm would be sore. So, if you get an injection back there, or in some cases two, using that muscle in opening and closing can frequently elicit pain for several days afterwards.

Your TMJ (Temporomandibular Joint)

The second source of pain while opening after a filling can be from the actual jaw joint, known as the TMJ (temporomandibular joint). This is the area at which your lower jaw bone connects to the base of the skull.

Your jaw joint was made for all of your daily activities – talking, smiling, eating normal foods, etc. The joint was not designed for “abnormal” tasks such as gum chewing, chewing on ice, or holding your mouth open for your dentist or hygienist to work.

photo of TMJ in a skull which can have pain after opening

The temporomandibular (TMJ) joint. Pain in this joint as well as the muscles and ligaments associated with the joint can occur after a dental visit.

Here’s another analogy: imagine standing on the tips of your toes. Now do this for 5 minute intervals several times, with perhaps 30 second breaks in between. Do this for approximately 45 minutes. Don’t you think that the next day, moving that muscle and the joints would be sore? This assumes you are not a ballet dancer.

A cleaning or a filling of moderate duration will be a lot like the above. Lots of straining to keep your mouth open, which can lead to fatigue and soreness in the muscles and joint. This can then result in pain and soreness on opening for several days.

Some Assumptions

We find that one or both of these reasons are responsible for the pain and soreness approximately 99% of the time. There are other circumstances which can include:

  • Infection of either a tooth or an infection at the injection site.
  • Pain after a surgical procedure such as a lower wisdom tooth extraction.
  • Aphthous ulcers (cold sores) in the back of the throat.
  • Upper respiratory infections, etc.
  • And many others.

Of course there can be other explanations. But for the vast majority of the time, the pain is either from the actual injection or in joint after being open for a prolonged period of time.

The Palatal Injection: Dentistry’s Most Painful Shot

Probably the most frequently commented upon topic on this blog involves what the majority of patients dread the most: the shot. As a result, I’ve posted many articles related to dental injections, including articles on novocaine (no, we don’t use it anymore), epinephrine (the racing heart does not mean you are allergic to it), why some people/teeth are hard to get numb (over ten different reasons), etc.

I’ve also done a two part series on what factors cause some dental injections to hurt more than others (located here and here). However, given the number of comments and questions about palatal injections, it was warranted to create an individual post on what can be considered dentistry’s most painful injection.

What is a Palatal Injection?

This may seem somewhat obvious but it is worth explaining. We’ll start with a photo.

palatal injection photo - most painful dental shot

Injection into the palate on the right side. If it looks painful, it’s because it is painful.

In a palatal injection, local anesthetic is injected into the soft tissue covering the hard palate, just adjacent to the tooth/teeth to be worked upon. It is not an injection into the soft palate nor the uvula. And it is only done for top teeth.

These types of injections are performed when you need the gum tissue on the roof of the mouth to be numb and/or when the procedure requires the tooth to be super numb (like an extraction or root canal). In my experience, for most fillings of upper teeth, palatal injections are NOT needed.

Why Palatal Injections Hurt so Darn Much!

There are two major reasons to explain why these hurt so much:

Tightness/Density – the tissue lining the hard palate is very dense and tight. There’s no “give” to it. The needle initially goes in and is accompanied by a pinch. That pinch is actually not the worst part. The worst part is when the local anesthetic fluid is forced in. There’s literally no room for it because the tissue is so dense. That forcible entry of fluid into this tissue is what causes the pain.

Topical anesthetic does not help with palatal injections

Traditional topical anesthetic does little to help with palatal injections.

Want an analogy? Imagine you have a turkey baster injector. Plunge the injector deep into the breast or thigh. Then try to inject. It will take GREAT force to get even a little fluid into this dense muscle. This is like a palatal injection. Next, move the tip of baster until it is just at the border of the thigh and skin. Then try to inject. There is little to no resistance. Fluid goes in with great ease, taking advantage of the looseness at the skin/muscle junction. This is like most other dental injections.

Traditional Topical Anesthetic Doesn’t Work Well – traditional topical anesthetic, a.k.a numbing jelly, doesn’t penetrate the tissue very easily, regardless of how long you wait. As a result, it exerts little to no effect, thus offering little to no pain relief.

How Palatal Injection Pain Can be Reduced

Fortunately, there are ways to reduce the pain associated with palatal injections. Note, however, that these are all done by the dentist himself/herself (except the last one which involves both dentist and patient).

  1. cotton applicator applying pressure can reduce pain of injection on the palate

    Application of pressure can reduce the pain.

    Waiting – in nearly all cases, if you are going to get an injection on the palate, you will also receive an injection on the cheek side. In many cases, if the dentist waits 10 minutes or so after the “cheek side” injection, some of that local anesthetic will work its way over and partially anesthetize the palate. This will make it so that the palatal injection is less painful.

  2. Pressure – placing firm pressure with a cotton applicator for at 30 seconds can slightly numb or obtund the pain sensation. The pressure is applied on the roof of the mouth right where the injection is going to go.
  3. Super Topical Anesthesia – some dentists will use a pharmacy compounded topical anesthetic that is several times more powerful than traditional topical. Using this correctly can also reduced the pain.
  4. Cold – application of a cold cotton applicator with pressure right before the injection can also reduce the sensation.
  5. Sedation – if you are sedated, you are unlikely to even feel the painful injection, let alone remember it. Sedation dentistry is very effective – I do it routinely in my office.

Not all dentists employ the above techniques. But all dentists are aware of the painful nature of this injection and do their best to only do it when necessary.

 

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.

Dental Local Anesthesia and Ehlers Danlos Syndrome

Ehlers Danlos Syndrome is a group of similar inherited disorders that adversely affect the connective tissue. Patients with this disease experience problems in the skin, joints, blood vessels, and other areas. In addition, some disorders within the syndrome also make the individual resistant to local anesthesia.

Unfortunately very few dentists are aware of this phenomenon. And in addition, there are patients out there with undiagnosed Ehlers Danlos, as well as patients with EDS who are not aware of the issues with local anesthesia. What happens? The patient ends up having a very unpleasant time at the dentist with both the dentist and patient trying to figure out what is going on!

About Ehlers Danlos Syndrome

Ehlers Danlos and dental local anestheticIt is not the point of this blog post to talk about the Syndrome in great detail. There are plenty of other sites out there that accomplish this. However, to understand how this affects dentistry and the dreaded “novocaine shot,” you need to know a bit about the disease.

Ehlers Danlos affects connective tissue. Connective tissue is basically the “glue” that holds other tissue and organs together. Specifially, there are defects with the production of collagen, which is the major protein in connective tissue. While there are six major types of EDS, they are all generally characterized by hypermobile joints (joints that can move way beyond what would be considered normal), joint pain, fragile and easily bruised skin, and other findings.

Not all of the genes responsible for Ehlers Danlos are known and there is active research into all parts of this syndrome.

Why Does Local Anesthesia Not Always Work?

First, it needs to be mentioned that not all of the six types of EDS make the patient resistant to dental local anesthetic. Based on research (here and here), it appears that Type III – Hypermobility is the one in which this phenomenon is seen.

dental injections don't always work in Ehlers Danlos

For those with some types of Ehlers Danlos, you will need MANY injections of very specific anesthetics for effective local anesthesia.

Unfortunately, the mechanism behind why the local anesthesia is less effective is not well understood. The current theory focuses on the “looseness” of the connective tissue. Since the connective tissue is defective, it is very easy for the local anesthetic to quickly move away from the site that is being anesthetized. Stated another way, the connective tissue barriers that hold the local anesthesia in place for the duration of the dental procedure are weak and easily broken.

The end result is that the patient is not sufficiently numb for the dental procedure, leading to pain. Patients get confused, discouraged, angry, and ultimately avoid the dentist, which then makes things even worse down the road.

What Should Dental Patients Do?

Ehler Danlos hypermobility which can affect dental local anesthesia

If you can do this with your thumb, you may have Ehlers Danlos.

As a dentist who treats patients in private practice, I am disappointed that this issue is not well known in the dental community. Ask most dentists and unfortunately, most will not be aware of this. In fact, in what is considered the bible of dental local anesthesia (A Handbook of Local Anesthesia by Stanley Malamed), there is no mention of phenomenon (I searched the 6th edition).

Here are some tips:

  1. Find a dentist who has experience with Ehlers Danlos. There is nothing wrong with calling an office and asking if the dentist is familiar with EDS and this local anesthetic phenomenon.
  2. Identify yourself early on as having Ehlers Danlos to the hygienist and dentist.
  3. Find an opportunity to meet with the dentist in advance of any procedure requiring local anesthetic to review the plan (remember that the office may have to order a special type of local anesthetic).
  4. Consider taking a medication beforehand to relax you.
  5. Be ready for a longer than normal appointment.
  6. At the completion of the appointment, especially if it was successful, ask the dentist for detailed records on the local anesthesia (what local anesthetic, how much administered, where administered, etc.)

In some cases, nitrous oxide and/or IV sedation may be necessary to complement the local anesthesia.

My own experience treating patients with Ehlers Danlos has shown that most of the time, we can achieve local anesthesia. I attribute my success to knowing the pharmacology of local anesthetics as well as other injection techniques. To use a pun based on EDS, with a little “flexibility” in selecting local anesthetics and injection sites, we can nearly always succeed!