Objective: To probe deeply into the traumatic characteristics and the neurobiologic mechanism of overextended mouth opening of the temporomandibular joint (TMJ).
Methods: Changes of the substance P-like immunologic reaction (SPIR) of the TMJ soft tissues were examined with ABC immunohistochemical staining along with the histopathological study of the overextended opening.
Results: An obvious increase of SPIR brought about by overextended opening was mainly in the anterior extending tissue of the disc, the bilaminar zone and the subsynovial layer of the articular capsule, and the extent of the reaction became greater with the increased duration of over-opening. The SPIR decreased obviously two weeks after removing the nocuous stimulation. The changes of SPIR almost coincided with the histopathological changes in sites and extents, and in the effects on them of the relevant treatment, which indicate that there are some internal relations between the two kinds of changes.
Conclusion: To recognize the characteristics of the changes and grasp the internal relations will help us to find new approaches to the prevention, diagnosis and treatment for the trauma and pain of the TMJ.