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Syllogism about the temporomandibular joint

Definitions of syllogism:

•A kind of logical argument that applies deductive reasoning to arrive at a conclusion based on two or more propositions that are asserted or assumed to be true.
•Formal reasoning disassociated from reality.


Disc displacement without reduction

Disc displacement without reduction

I received an email from a certain TMJ guru and I could not help but see an association that is not founded and not justified between 2 statements that reminded me of my philosophy courses in CEGEP when I learned what a syllogism was.

Here are the statements that can be true if considered individually, but from which the conclusion is false due to an incorrect reasoning.

1-More than 50% of the population, as early as 20 years of age, have at least one displaced disc in at least one TMJ.

In reality, about 30% of the population have an internal derangement (disc displacement) that is ASYMPTOMATIC, meaning: no symptoms, no pain.

2-When the disc is displaced, the condyle is not as well protected anymore.

Truly, it is preferred to have an articular disc in the right place.

But it is rather the statement that is tendentious and at the root of a conclusion that does not reflect reality.
Indeed, every patient who suffers from disc displacement does not necessarily suffer from a degenerative joint disease.
And among those who suffer from a degenerative disease and disc displacement, the degenerative disease occurred first (therefore a change in the shape of the condyle), which may have triggered the disc displacement.

3-Therefore, it is at risk of not growing properly if it occurs during infancy (for instance following a trauma) or at risk of degenerating.

A second tendentious statement.

He confuses 2 problems: trauma and disc displacement.

A trauma (like a hit or a fall on the chin) causes an ischemia (a bruise, a hematoma) in the joint that affects cartilage formation. Any reduction in cartilage formation in the condyle leads to a slower growth.
A disc displacement will cause a problem only if an inflammatory reaction follows. A disc displacement without inflammation does not mean that growth will be affected.

4-When a condyle undergrows or degenerates, the occlusion is more posterior.

This is true, but the patient does not need to suffer from disc displacement to have a degenerating condyle.

Moreover, condylar resorption may also occur in young adults for whom growth has stopped.

5-A more posterior occlusion puts an increased pressure on teeth and makes them at risk of premature destruction.

What does he mean by posterior occlusion? A mandibular retrognathia, an occlusal prematurity on posterior teeth.

Indeed, condylar shortening or resorption causes a rotation or a posterior displacement of the lower jaw, but the posterior displacement is the consequence of the condylar resorption rather than the cause.


A temporomandibular joint must be considered as any other joint in the human body. As such, it may be prone to arthrosis. Having teeth located on the other end (or between the left and right joints) does not mean that teeth (or the occlusion) are causing arthrosis.

The syllogism is the link between an internal derangement of the TMJ, the condylar resorption and the lack of growth of the joint cartilage.


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