Trismus: Often Confused with Lockjaw

The layman’s term for Trismus is lockjaw.

The question is “what is Trismus?”

Is it when you can’t open as wide as you normally would be able to (normal mouth opening is 35-45 mm) or is it when you’ve already opened wide and as a result of opening wide, your jaw gets stuck and now you can’t close it?

Technically, the answer is the first. Trismus can precipitate the lockjaw, but the lockjaw itself doesn’t necessarily lead to or cause trismus.

Trismus itself is not a disease… is a symptom of other problems which will be discussed in the next couple of blogs.

Trismus can develop slowly or suddenly…someone undergoing radiation therapy may develop Trismus slowly. It may go unnoticed for a while and then appear. An individual who is involved in a car accident and has trauma to the jaw can develop Trismus suddenly.

The definition of trismus can be a little gray…
1) An inability to open the mouth.
2) Limited mouth opening.
3) Limitation of movement of the jaw.

When Trismus is left untreated it can often become serious enough that one can develop problems relating to swallowing, speech and oral hygiene…when you think about it, this makes sense since it’s more difficult to do these ‘actions’ without being able to open one’s mouth.

Pain may also become an issue. The severity of trismus and the length of time that it lasts depend on its cause.

Let’s discuss the causes of Trismus

The causes are discussed as they relate to the Temporomandibular Joint (TMJ) itself. This may be a good time to re-read the TMJ series of blogs that were posted on October 12th and run until November 12, 2011.

Trismus can occur:
1) Within the TMJ (inta-articular) – This is within the disc area of the TMJ and its surrounding area. This is one of the most common causes of Trismus.
2) Outside of the TMJ (extra-articular) – This involves ‘issues’ outside of the disc area, I.e. the muscles/nerves of the head and neck.

The next few blogs will look at the intra and extra articular causes of Trismus, and the expected duration, prevention and treatment of it.

Until the next time,

Yours in good dental health!

Dr. F. Keshavarz Dentistry, Brampton’s Gentle Dentist

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