Expressions of substance P in rat TMJ during occlusal reconstruction for unilateral chew

Objective To investigate the expressions of substance P (SP) in rat TMJ during occlusal reconstruction for unilateral chew,and to discuss the significance of the change of SP expression relevant for temporomandibular disorders.Methods Thirty Wistar male rats were randomly divided into 3 experimental groups and 3 control groups,5 rats in each group. The molar of right maxillary and mandibular in experimental groups were ground to the gingival level without occlusal contact. The occlusal contact was recovered by stoping grounding molar of the rats. The sections of disc and articular capsule were immunohistostained for SP by using SABC method. The sections of disc and condylar process were also stained for HE. Light microscope and microscoic photo analytic software and SPSS10.0 statistical software were used.Results The areas of substance P-like immunoreactive (SP-LI) nerve fibers in unilateral chew experimental group were obviously larger than those in control group (P0.01,P0.05). The increased extent in non-chewing side was much higher than that in the chewing side (P0.05). There was no significant difference in the areas of SP-LI nerve fibers between the early occlusal reconstruction experiment group and the control group (P0.05) and there was also no significant difference between the non-chewing side and the chewing side (P0.05). There was a significant difference in the areas of SP-LI nerve fibers between the later occlusal reconstruction experiment group and the control group (P0.01,P0.05) and the non-chewing side and the chewing side (P0.05). The TMJ of early occlusal reconstruction experiment group were showed normal. There were some pathognostic changes in TMJ in later occlusal reconstruction experiment group.Conclusion The expressions of SP can recover to normal level in the early occlusal reconstruction,but not in the later occlusal reconstruction. SP might participate in the histopathologic mechanism of temporomandibular disorders. Early occlusal reconstruction may be important for prevention of development of temporomandibular disorders.