In dentistry, orthodontics, and oral and maxillofacial pathology, the body part in question is usually the mouth, tongue, or jaw.
Normally, the temporomandibular joint (TMJ) acts as a class III lever, which helps to restrict the amount of force generated.
When a person senses the risk of an imminent car crash, for example, the teeth arches are normally firmly occluded.
This overclenching is still considered parafunctional, although it serves a functional purpose; the maxillomandibular complex is much less vulnerable to harm and dislocation because it is bonded by muscles and interposed teeth.
[citation needed] It is one hypothesis for why military jet pilots crack more teeth than auxiliary crew.