Every time we talk, chew, bite down, or swallow we put the temporomandibular joint (TMJ) to work.  With excessive force, overuse or misalignment, TMJ Syndrome starts causing pain in the muscles and joints of the jaw.  This pain may radiate to the face, neck, head and even to the shoulders. There also may be difficulty opening the mouth all the way, along with clicking or popping noises when chewing, yawning or moving the jaw.  The most common causes of TMJ are a poor bite and stress combined with tooth-grinding, especially at night.  Gum chewing can make the problem even worse.  Headaches are a common symptom.