This old article/ link shows the basic causes of tinnitus. Every word is important. Jastreboff, Levine and other Who's Who researchers have noted research in this article. They had it right years ago. Most with T will see their tinnitus fade or will be able to adjust. The younger the quicker.
It's not so much due to what caused the T, including an accident, neck, jaw, ear relations, disease and hypertension - it's to what extend the brain activates signals. High pitch ringing can be caused by many things in which many are somatic/physical related.
There's five areas of the neck that are primary responsible for somatic tinnitus. In order they are the trapezius muscles, SCM muscles, c spine, vagus nerve and jugular veins. With the mouth/TMJ, there's nerves and joints. Hopefully within the mouth, a major nerve wasn't cut.
Whenever serious problems of nerves, joints, muscles, disease and major hearing loss are heaving involved, then usually it's high pitch ringing. Very few has extreme high pitch ringing. If they did they wouldn't be posting here. Even with those, not a ENT or neuro this or that, but a pain management physiology rehab doctor can often help them.
Electrical head tinnitus is often caused from circulation, swelling and physical nervous system reactors (spine) from nerve pressures. Touch therapy will help.
http://vestibular.org/tinnitus
Many times with proper treatment, physical T can be corrected. It's harder with degenerative conditions and disease mostly found with other people, but improvements with proper treatment will help those as well.