Effects of prolonged chewing upon the functional symptoms of internal derangements of the temporomandibular joint

Clicking of the temporomandibular joint (TMJ) is one of the typical clinical
manifestations of internal derangements (IDs) of the TMJ. The two main types of
IDs are anterior disc displacements (ADD) and hypermobility. IDs are, in
general, not a source of complaints, and are therefore not treated, except in
cases when (temporary) joint locking occurs. However, the cause or trigger of
locking is not known. Certainly, the presence of an anatomic predisposition is
required, i.e., a presence of a displaced disc, or a condyle traveling beyond
the eminence. But besides these anatomical features, an additional factor is
needed. It has been suggested that masticatory muscle hyperactivity may
modulate the symptoms of IDs, and therefore may play an important role in the
onset of locking. Such hyperactivity is exerted mainly during oral
parafunctional activities.

To test the hypothesis that oral parafunctioning, viz. prolonged gum chewing,
has an effect upon the functional symptoms of internal derangements of the
temporomandibular joint. To test the hypothesis that the effect of the
above-mentioned oral parafunction is greater in ID- patients, i.e. subjects
diagnosed with an ID, and having signs of intermittent locking, than in ID-
participants, i.e. subjects, diagnosed with an ID, and not having such signs.

Experimental study.

Prolonged, bilateral gum chewing at a constant, controlled natural chewing pace
for a period of maximum 60min.

By participating in this study with duration of only two hours, the
participants benefit from the movement recording, as it is a diagnostic
procedure, as well as from the explanation, which they receive about their
internal derangement. Throughout the chewing phase of the experimental study, a
chance exists that fatigue and/or pain from the masticatory muscles arises.
These adverse events are, however, mild and transient, and besides a short
relaxation period, they require no further treatment. In case effects are
registered from prolonged gum chewing upon the functional characteristics of
IDs, i.e. upon the relative distance of disc reduction (for ADD) and upon the
acceleration of the condyle (for TMJ hypermobility), then these results will
form the rationale for a trial of treatment (i.e. counselling to avoid
parafunctions) in ID- patients, which is lacking so far. Therefore, gathering
data and obtaining results in this study will not only be beneficial to the
participating patients, but also to future ones.