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What Causes Lockjaw Symptoms? Donald Tanenbaum

What Causes Lockjaw?

Author: Donald Tanenbaum DDS MPH - Board-Certified Orofacial Pain Specialist at New York TMJ & Orofacial Pain

Date: January 23, 2018

Suffice it to say, if you wake up one morning and your jaw is locked shut, you’re going to be extremely frightened. You have lockjaw clinically known as trismus. As a TMJ and orofacial pain specialist, I see many patients every year with lockjaw. So, what causes lockjaw, and is there anything you can do about it?  

Before I answer that questions, I need to explain a bit about how our jaws work. The jaw joint is essentially a hinge and is controlled by four muscles: 1) the masseter 2) the temporalis 3) the internal pterygoid 4) the external pterygoid. These names may sound like extinct dinosaur species, but they are very delicate muscles that together perform the important job of opening and closing the jaw and moving it from side to side.

There are two causes of lockjaw –  jaw muscle spasms or impaired, incapacitated or shortened jaw muscles. To determine if your jaw is opening normally try this – open your mouth and insert three full fingers horizontally with your fingertips facing into your mouth. If they fit easily, you’re in good shape. If they don’t, read on:

What Causes Lockjaw Is A Variety Of Behaviors & Conditions  

Here’s what can cause lockjaw:

1) Daytime Behavior

When over-used, your jaw muscles, just like most other muscles in your body, can become fatigued and go into spasm. This results in pain, limited motion, or both. If you’re a gym rat, you’ve probably experienced that sensation from over-working your hamstring or calf muscle – limited motion, pain, or both. Your jaw muscles behave in exactly the same way.

Many types of daytime behavior can cause lockjaw. Your jaw muscles can become fatigued from excessive gum chewing, prolonged contact between your upper and lower teeth, frequent nail-biting, and if you keep your teeth clenched for long periods of time.

Prolonged tension in your upper neck can also cause lockjaw. Your jaw muscles can become shortened then it’s impossible for you to fully open your mouth. If you’re under a tremendous amount of stress, feel anger, discontent, worry, anxiety, or fear during a long period of time can be the cause of lockjaw symptoms. 

However, millions of people chew gum, clench their teeth, and bite their nails and they don’t develop the symptoms of lockjaw. In my field, orofacial pain, we consider those behaviors risk factors – as opposed to being the cause of lockjaw symptoms. 

2. Temporomandibular Joint (TMJ) Problems
Your jaw joints are also known as TM joints, are literally hinges that allow your top teeth and your bottom teeth to move independently of each other. Problems that arise in the TM joints can lead to jaw pain, jaw clicking, and lockjaw, to name just a few. The cause of lockjaw symptoms in these cases is a result of pain, muscle tightening, spasms, or mechanical interferences in the hinge itself. 

3. Jaw Trauma
Trauma, such as from an auto accident or sports mishap, that has caused a fracture, inflammation, muscle bruising, hematoma formation, a sprain in the TM joint can cause lockjaw. A change in the joint’s anatomy can cause it as well.

4. Cancer Therapy
Cancer therapy, such as radiation to address head or neck cancer, can cause the jaw and neck muscles to become less flexible and lead to symptoms of lockjaw. 

5. Head Or Neck Tumors

Certain tumors in jaw muscles and/or in the TM joint can cause lockjaw symptoms, as well. Tumors in the throat, larynx, pharynx, thyroid, parotid gland, or ear can also be culprits.

6. Tetanus
Most people already know that tetanus can cause lockjaw. Thankfully, modern medicine has made tetanus very rare in the United States today. It’s a bacterial infection that causes muscle spasms that most often start in the jaw then progress to the rest of the body. 

7. Other Infections
Infections such as those associated with impacted wisdom teeth, infected tonsil, or infected salivary glands can also cause lockjaw. 

8. Dental Work

Dentists often need to use a mandibular block injection with a local anesthetic to comfortably treat a patient’s lower molar tooth or to remove a lower wisdom tooth. Mandibular block injections are performed millions of times a day with no problems. But on rare occasions, a patient may wake up unable to open their mouth. This is sometimes accompanied by jaw pain that can last for a few days after the injection. The cause of lockjaw, in this case, is trauma to a nearby muscle, bleeding, too much anesthetic or a slowly-developing infection.

How Lockjaw Symptoms Are Diagnosed

To diagnose lockjaw, your doctor needs to identify the cause or risk factors associated with the symptoms. Every lockjaw situation is accompanied by some limited jaw motion. Some lockjaw symptoms include pain and soreness. Sometimes there is no pain at all – just restricted motion. A clicking jaw joint that suddenly doesn’t click anymore can be a clue, too. Your doctor may order x-rays, a CAT scan or an MRI of your TM joints, your head and/or neck depending upon the clues uncovered from your history and exam.

Every patient is different and in order for your medical professional to discover in your case what causes lockjaw it’s critical that you explain in detail what was going on right before your symptoms emerged. 

How Lockjaw Is Treated

Once your doctor has figured out what causes lockjaw in your case, he or she will develop a treatment plan tailored for you. Your plan might include jaw exercises, warm moist heat applications, anti-inflammatory medication  or antibiotics for a short period of time. Physical therapy may be recommended, as well.

For you, what causes lockjaw is only the start. A full recovery can take several months. It’s important to be patient. 

DISCLAIMER: The advice offered in response to your questions is intended to be informational only and generic in nature. Namely, we in no way offer a definitive diagnosis or specific treatment recommendation for your particular situation. Our intent is solely educational and our responses to your actual questions serve as a springboard to discussion of a variety of dental topics that come up in a day-to-day dental practice. Any advice offered is no substitute for proper evaluation and care by a qualified professional.

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