| Summary: | The biomechanical events that accompany functional loading of the
human mandible are poorly understood. Computer simulations has emerged as an
indirect way to demonstrate the principles of jaw mechanics. The modelling of
condylar load distributions for various clenching tasks has lead to the observations
that deviations in form and osteoarthritic changes as most commmonly found in the
central and lateral regions of the articulation reflect habitual compressive loading of
the temporomandibular joints.
Speculation has existed that compressive stresses as measured during
simulated unilateral tooth clenching, offer a functional correlate for regional differences
in articular pathology. It has been suggested due to the indirect measuring of the
effects of these loads, that well-known progressive deterioration of the discs and
articular surfaces are largely brought about by persistent non-working side
compression of the temporomandibular joint structures. This in the short term is
believed to lead to arthralgia of sufficent magnitude that patients often seek treatment
by dental clinicians.
In the first study, an existing 3D FEM model of the human mandible,
modified to include an opposing oral orthopaedic device, was utilized to test for the
effect of two clenching tasks on the compressive stresses measured at the level of the condylar heads when an orthopaedic dental appliance with unilateral occlusal contacts
was placed between the teeth. It was found that the level of compressive stress in the
contralateral side is twice that of the working side joint.
A clinical study was then performed in order to test the hypothesis that
in acute articular pathology, the use of an orthopaedic appliance designed to reduce
the load to the painful joint can positively influence the resolution of arthrogenous pain
in the short term. Specifically, it was proposed that this could be achieved with an
appliance designed with unilateral occiusal support.
A group of patients diagnosed with unilateral articular pathology were
randomized into two treatment groups, one was treated with a conventional flat
appliance, the other with unilateral occlusal contacts removed from the side
contralateral to the painful joint. In both cases, a VAS was used to assess pain in both
joints with and without the mechanical stimulus provided by biting on a force
transducer placed between the teeth. Patients were followed for 3 weeks after initial
testing. It was found that painful symptoms improved in the range, as measured by
the VAS, and in the degree of pain for subjects treated with the unilaterally supported
appliance, It was also discovered that the range and magnitude of the bite force
increased concomittantly with the reduction in painful symptoms. Collectively the studies suggest that muscle activity is sensitive to
differences in occiusal support offered by an intra-oral appliance, and that such a
device can be used to modify articular loading and/or to control muscle use in such
a way as to speed up the resolution of painful intrarticular symptoms in TMJ patients.
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