The inflammatory process is a coordinated response that protects host after infection or trauma, involving several molecular reactions. Once the inflammation is closely linked to the process of destruction of the temporomandibular joint, this study aims to examine, by immunohistochemistry, the expression of interleukin-6 (IL-6), an important inflammatory marker, in temporomandibular articular discs of patients with anterior disc displacement with (ADDwR) and without reduction (ADDwoR) and its association with osteoarthrosis (OA). Thirty-eight (n = 38) articular discs were divided into two cutoffs: 1) analysis 1: 4 control (acute pathology), 17 ADDwR, 17 ADDwoR; and 2) analysis 2: without OA (n = 21) and with OA (n = 17). The area of immunostaining was compared statistically between groups (p < 0.05). In the disc samples, no significant differences were observed between the groups ADDwR and ADDwoR, and with and without OA, in respect to the expression of IL-6 by immunohistochemical examination. Future studies should be conducted with a larger sample size, which could clarify the association of the inflammatory mediator IL-6 with temporomandibular joint dysfunction.

Purpose: Matrix metalloproteases (MMPs) are tissue-remodeling enzymes that function during the remodeling process, such as in immune-inflammatory diseases. Metalloprotease-2 (MMP-2) and metalloprotease-9 (MMP-9) are gelatinases that degrade several types of extracellular matrix collagen. It is hypothesized that in temporomandibular joint (TMJ) dysfunction, MMP-2 and MMP-9 expression levels may be elevated. Therefore, the objective of this study is to determine the association of MMP-2 and MMP-9 expression with temporomandibular joint dysfunction using an immunohistochemical approach to evaluate the joint disk. Material and Methods: A total of 45 human temporomandibular joint samples were collected, with 36 samples in the test group (patients with anterior disk displacement with reduction (n = 29) and without reduction (n = 7)) and nine samples in the control group. The immunostaining of the TMJ disks was statistically compared between the groups (P < 0.05). Results: There was a statistically significant difference for the area of MMP-2 immunostaining between the control group and the displacement disks with reduction group (ADDwR) (P = 0.048) and between the groups with disk displacement and without reduction (ADDwoR) (P = 0.029). The expression of MMP-2 was significantly elevated in the ADDwoR group. Conclusion: No statistically significant difference was found between the variable area of MMP-9 expression in the disk with and without disk displacement, as determined by immunohistochemical analysis. However, there was an elevation of MMP-2 expression in the disks of patients with displacement and without reduction (more severe alteration).

A higher area of in situ immunostaining of FasL was found in temporomandibular discs with reduction, which is the less severe condition. Moreover, a reduced expression of FasL in the discs of patients with osteoarthrosis was found, suggesting that some aspects of apoptosis might underlie the progression of TMJ disorders.

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