A night guard( occlusal appliance) is generally highly effective for relieving tmj symptoms. However, it depends on who fabricates the appliance. If an occlusal appliance is well made, you would feel the joints position in a upward and backward direction while closing your jaw, a non-effective appliance would tend to move your jaw further forward, comparing to your closed jaw position while not on appliance.In addition, cheek muscles tend to relax shortly after the well made appliance is oplaced in the mouth. Clenching habit is generally eliminated.
Seeing a competent tmj specialist is advised.
See an oral surgeon. My daughter suffered with TMJ for years before it was hardly known to the public. Her jaw was out of line and tilted. The hinge where the jaw bone is connected under the the hairline area about ear level has cartilage. When the bone is out of line it will slide across and wear out that lining and can cause arthritis. When the mouth is shut it does not close properly meaning the muscles cannot relax causing much pain. My daughter went through surgery to correct hers and wore braces also. A good oral surgeon should be able to help you. RJ