A patient with an unstable TMJ has soft tissues that have not adapted and bone that continues to deteriorate and lose dimension. An unstable TM will cause progressive bite and facial skeletal profile changes. These patients are often categorized as having Piper Classification Stage IVa, Stage IVb, or Stage Va joints.
A patient with an unstable bite cannot reach maximal intercuspation, which is when the tips of the teeth of both the upper and lower jaw interlock, and there is premature contact in the posterior or anterior teeth.
The most common pain source is the muscle. In an unstable patient, the chronic pain patient will have multiple layers of pain, such as migraines, nueralgia, and teeth pain.
A patient with an unstable functioning jaw may have reduced range of motion, reduced vertical opening, and chronic or intermittent locking.