Histological investigations on the influence of dexamethasone on rat temporomandibular joint induced arthritis

In this study, 30 female Sprague-Dawley rats were used and were divided into three groups including: group (I): the control group involved 10 female rats, group (II): involved 10 female rats subjected to osteoarthritis induction without treatment, group (III): involved 10 female rats treated with dexamethasone after osteoarthritis induction.  Experimental procedures in osteoarthritic animals a single dose of Formalin (1.5%) or its vehicle (0.9%NaCl) was unilaterally injected in the TMJ (30µL) with a Hamilton syringe connected to a 30_gauge needle introduced into the TMJ at the moment of injection.  After 1week post osteoarthritis induction, the treatments with Dexamethasone will be administered for 4 weeks as follow:  Group III: the experimental animals were treated with a single dose (50µL) of   0.12 mg dexamethasone via intra-articular route as prescribed previously. After osteoarthritis induction, in group (II), fusion between disc and condyle, condensation of the cells in the fibrous layer, approachment of bone marrow spaces to the cartilagenous layer, defaseiculation of central part of articular disc, Chondrocytes appear condensed, degeneration of numerous cells, variable in size and pyknotic nuclei, erosion in the condylar fibrous and cartilaginous layer, synovial membrane became extensively proliferated to develope synovial villi into the temporodiscal space.  After treatment with dexamethasone, in group (III), the histopathological features became significantly lowered after the treatment with dexamethasone when compared with the control group, the inflammatory reactions had been inhibited, although slight hyperplasia of the synovial membrane cells, the condylar cartilage appeared of variable thickness while the chondrocytes showed marked proliferation, variable in size and irregular distribution.