It is noted that reactive oxygen species (ROS), comprising free radicals such as hydroxyl radical and superoxide anion, are extremely reactive molecules normally, produced through normal metabolism and cellular breathing. Below usual physiological state, free radicals can also behave as triggering molecules included in cellular mechanism, for example signal transmission of numerous gene expressions. Gathering of extra free radicals in a tissue results in a pathologic state by injuring intracellular and extracellular molecules as well as extreme activation of cellular procedures, such as DNA injury, lipid oxidation or denaturation of protein. To manage free radical facilitated reaction, antioxidant enzymes [e.g. superoxide dismutase (SOD),] presented in the body that function to transform extremely reactive free radicals to a smaller amount of active molecular types(21). Furthermore, low-molecular-weight antioxidant, such as, glutathione, ascorbate scavenge free radicals as they are generated in metabolically active tissues. Free radical responses and oxidative destruction are in the majority of situations detained in check by aforesaid antioxidant defence tools, but where an extreme quantity of ROS are generated or defence methods are harmed, oxidative damage such as lipid peroxidation can emerge. Such type of disturb among composition of ROS and antioxidant defence structure was accomplished certain as oxidative stress. It has furthermore been claimed that mechanical stresses may cause to ROS-induced oxidative stress of the temporomandibular joint (TMJ). Extreme generation of oxidative stress in the TMJ then results in tissue harm, which advance promotes to TMD(22).
In this study the relationship between mean salivary level of some of antioxidants (Glutathione reductase, Catalase and Free thiol) and TMD were analyzed. There was a significant reduction in Glutathione reductase and Catalase level in TMD patients in comparison with healthy people; due to the click, pain mechanisms, and severity of TMD (Helkimo index), which means these antioxidants were affected by TMD. To the best of our knowledge there was not found any similar study that assessed salivary level of these antioxidants in TMD. (However, various researches assessed other antioxidants level in TMD patients that we compared them with our study. in accordance with present study) Orhan et al discovered that the action of SOD appeared to be increasingly declined as the stage of the temporomandibular joint internal derangement increased. However, they evaluated synovial fluid of patients with temporomandibular joint internal derangement and proved the association between the action of SOD and the stage of the disease. (23).
Confirming the finding of the present study, Lawaf et al measured the total antioxidant capacity(TAC) of saliva and serum of TMD patients. They assumed that the mean plasma TAC in TMD patients with/without pain was meaningfully lower than control group but no significant distinction was detected in salivary TAC between their groups(24).
Suma et al, proved in their experiments on brain tumor patients whose salivary protein thiol levels were significantly raised(25), although the condition of their patients was different from our patients, maybe with the reduction of free thiol in reduced form of intracellular glutathione, there was another compensating way with another form of extracellular free thiol protein and the final measurable free thiol remained constant in our results.
According to this study, age and gender have no relationship with antioxidants level. So the level of antioxidants is not affected by age and gender of the patients.
In accordance with our result, Demir et al also surveyed relation between expressive features (gender and age) and serum stages of malondialdehyde (MDA), an oxidative stress indicator, and antioxidant enzymes glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) in TMD patients. They discovered that there were no changes among the groups for gender and age. There was no relationship among gender and age and SOD, MDA, GSH and CAT levels in the TMJ disorders or control group. They finally decided oxidative stress indicators might have promising capacity as biomarkers in the diagnostic approach and therapeutic goals of TMJ disorders(26).
As we found in this study, Ishimaru et al, surveyed the relationship among the antioxidant volume of synovial fluid and radiological outcomes of intra-articular structures in patients with disorders of the temporomandibular joint (TMJ), they clarified that there is a relationship among the oxidative stress of the synovial fluid and closed-lock in disorders of the TMJ(27). They perceived that there is a significant decrease in antioxidant volume of synovial fluid of patients with close lock, as we showed there is decrease in antioxidant capacity of saliva in patients with click and the relation between click and decreasing antioxidants values.
In contrast, Almedia et al perceived as a result, the oxidative stress index (OSI) was meaningfully greater in the TMD and pain group. There was no relationship among Visual Analogue Scale (VAS), total antioxidant capacity (TAC), and total oxidant status (TOS) values. They discovered, oxidative changes appear to effect the pathogenesis of pain in TMDs (28). Our results are in according to their results which there is decrease in antioxidants values in those patients with pain and there is significant relationship in having pain and decreasing antioxidants.
Ahmed Fleifel et al revealed Oxidative stress of SOD and MDA was raised while GSH was declined. Based on these outcomes they decided that Oxidative stress is related in the pathogenesis of the temporomandibular joint disorders. The antioxidant agents might be deemed in managing of TMJ pain and dysfunction to inhibit probable elevated oxidative stress(29).
Tomida et al researched the redox status of albumin in the synovial fluid from patients with temporomandibular joint (TMJ) disorders (TMD).They discovered that the TMJ is marked by intra-articular oxidative stress, and the seriousness of TMD relates closely with the amount of oxidative elements(30). We also perceived decrease in GSH in our results and the relationship between oxidative stress, click and TMD; that decreasing antioxidants or increasing oxidative stress affects TMD situation. Although Tomida analysed on albumin in synovial fluid but their results is in accordance to our findings.
Ege et al investigated on serum prolidase action and oxidative stress in patients with temporomandibular joint internal derangement (TMJ-ID). They assumed meaningfully elevated prolidase action and oxidative stress in patients with TMJ-ID; they also found there was no important difference in GSH among groups(31). Our results were different from their result in GSH content which may be because of measuring serum instead of saliva or measuring only patients with internal derangement.
Limitation of this study: the sample size was small, another limitation of our study was discovering an approved laboratory to obtain reliable saliva test results. different labs and several kits were assessed and the reliability and validity of the one, used in our study, were proved.