including spray and stretch, medications, trigger points injections, prosthetics, orthodontics, TENS, and surgery...all of which are responding to an on-going activity which is either causing, or perpetuating the patient's signs and symptoms, that the splint failed to resolve.
If the patient's parafunctional activity were primarily of the lateral pterygoids (a), the splint (1) would be effective at relieving the strain to the jaw and face by providing less resistance to side-to-side move of the mandible.
If the patient's parafunctional activity were primarily
of the temporalis (b), the same splint (2) can serve
to make the patient's signs and symptoms worse, by providing a more efficient
surface to clench into. In patients with myofascial pain (a function
of clenching) who use a splint, 1/3 of patients show no change, and 1/5
of patients get worse (Q).
Ultimately, the occlusal scheme of a patient
does
not determine whether or not a person develops a temporomandibular
disorder (TMD) (R). The muscular activity
is independent of the occlusal scheme. (S)
The occlusal scheme modifies the forces generated by the muscular activity.
Modifying the occlusal scheme sometimes alters the force vectors generated,
thereby reducing or relieving symptoms.
Unless the clenching intensity is suppressed,
treatment for myofascial pain (headache) and TM disorders rarely
resolve the signs and symptoms, but serve in the attempted management of
the disorder (T).
(from an advertisement promoting a type of TMD therapy) |
The diagram on the left is an example of the misguided concept of TMD management.
Specifically, teeth do not "pull" the jaw off center. The opposing
cusps of an occlusal interference guide the jaw into maximal intercuspation
when the temporalis continues to contract, thereby elevating
the jaw even further. Normally, a posterior occlusal contact signals
the temporalis to cease its contraction, and for the lateral pterygoids
to initiate contraction, thereby re-opening the jaw. Occlusal
interferes are not the cause of the parafunctional conflict, but
act as a modifying variable to the presenting signs and symptoms.
As traditionally taught, an occlusal interference does not "cause the lateral pterygoid to spasm" . If a LP were to "spasm", the jaw would fly open. Since the LP's attempt at re-opening the jaw is met with resistance by the occluded teeth (maintained by the temporalis), the LP contracts isometricly, thereby presenting as dysfunctional. The pain is caused by the resulting strain that the isometricly contracting LPs put on its origin and attachment: the neck of the condyle and disc, and the pterygoid plate of the sphenoid bone. |
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