Occlusal trauma is the damage to teeth when an excessive force is acted upon them and they do not align properly.When the jaws close, for instance during chewing or at rest, the relationship between the opposing teeth is referred to as occlusion. When trauma, disease or dental treatment alters occlusion by changing the biting surface of any of the teeth, the teeth will come together differently, and their occlusion will change. When that change has a negative effect on how the teeth occlude, this may cause tenderness, pain, and damage to or movement of the teeth. This is called traumatic occlusion.Traumatic occlusion may cause a thickening of the cervical margin of the alveolar bone and widening of the periodontal ligament, although the latter can also be caused by other processes. Signs and symptoms
Clinically, there is a number of physiological results that serve as evidence of occlusal trauma:,
Progressive Tooth mobility
Fremitus
Tooth migration
Pain
Thermal sensitivity
Pain on chewing or percussion
Wear facets

Diagnosis
Microscopically, there will be a number of features that accompany occlusal trauma:
Hemorrhage
Necrosis
Widening of the periodontal ligament, or PDL (also serves as a very common radiographic feature)
Bone resorption
Cementum loss and tearsIt was concluded that widening of the periodontal ligament was a "functional adaptation to changes in functional requirements". Primary vs. secondary
There are two types of occlusal trauma, primary and secondary.
In primary occlusal trauma, the cause of the mobility was the excessive force being applied to a tooth with a normal attachment apparatus, otherwise known as a periodontally-uninvolved tooth. The approach should be to eliminate the cause of the pain and mobility by determining the causes and removing them; the mobile tooth or teeth will soon cease exhibiting mobility. This could involve removing a high spot on a recently restored tooth, or even a high spot on a non-recently restored tooth that perhaps moved into hyperocclusion. It could also involve altering ones parafunctional habits, such as refraining from chewing on pens or biting ones fingernails. For a bruxer, treatment of the patients primary occlusal trauma could involve selective grinding of certain interarch tooth contacts or perhaps employing a nightguard to protect the teeth from the greater than normal occlusal forces of the patients parafunctional habit. For someone who is missing enough teeth in non-strategic positions so that the remaining teeth are forced to endure a greater per square inch occlusal force, treatment might include restoration with either a removable prosthesis or implant-supported crown or bridge. In secondary occlusal trauma, simply removing the "high spots" or selective grinding of the teeth will not eliminate the problem, because the teeth are already periodontally involved.