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This study was undertaken to examine the alteration of masseter and plasma interleukin-6 after inducing occlusal interference and chronic stress. Male Wistar rats were submitted to chronic stress procedure, exposed to occlusal interference, or exposed to both mentioned procedures. Whole blood and masseter tissue were collected to determine interleukin-6 level, measured by means of ELISA. Masseter pain was evaluated using the orofacial formalin test. Masseter interleukin- 6 level was significantly higher in animals submitted to combination of occlusal interference and chronic stress than in the control group (p<0.05). There was positive and significant correlation between pain response and masseter interleukin-6 level (r=0.5741; p<0.0003). No significant differences in plasma interleukin-6 level were found between groups (p>0.05), as well as no correlation with pain (p>0.05). Combination of occlusal interference and chronic stress leads to strong local reaction characterized by high levels of masseter interleukine-6. High concentrations of muscle interleukin-6 and its correlation with pain point to inflammatory background of masticatory muscle pain.

The aim of this study was to investigate the prevalence and intensity of masticatory muscle and temporomandibular joint (TMJ) pain in Croatian war veterans with posttraumatic stress disorder (PTSD). The examined group consisted of 100 Croatian war veterans, in whom PTSD had previously been diagnosed. Patients were compared with 92 subjects who had not taken part in the war and in whom PTSD was excluded by psychiatric examination. The clinical examination consisted of palpation of the masticatory muscles, the prominent neck musculature, and TMJ. The examination technique used and the definition of items were previously tested for reliability and validity. 93% of the subjects with PTSD had masticatory muscle tenderness compared to 45.65% of the subjects in the control group (c 2=51.46, p<0.0001). The most frequent painful location in the subjects with PTSD was the left lateral pterygoid site in 88%, and in subjects of the control group the right lateral pterygoid site in 28.26% of cases. The most painful location in the PTSD group was the left lateral pterygoid site in 72%, and in the control group the left posterior digastric in 4.35% of cases. 58% of the subjects with PTSD had TMJ tenderness compared to 3.26% of subjects in the control group (c 2=66.23, p<0.0001). The most frequent painful location of TMJ in both groups was the left posterior capsule; in the PTSD group 38% and in subjects in the control group 2.17% of cases. The most painful location was the left posterior capsule in 28% of subjects with PTSD, while not one subject in the control group reported severe painful sensitivity. The very high frequency and intensity of pain in subjects with PTSD confirms the effect of stress on muscle and joint sensitivity, i.e. perception of pain.

This study aimed to investigate the individual effects of chronic stress and occlusal interference, as well as their combined influence on masseter muscle pain. Experiments were performed on 28 male Wistar rats. Animals were submitted to chronic stress procedure, exposed to occlusal interference, or exposed to both mantioned procedures. At the end of the procedure animals were submitted to orofacial formalin test, and nociceptive behavioral response was evaluated. Statisticaly significant diference of nociceptive behavioral response in chronicaly stressed rats and in the animals with occlusal interference in comparation to the control group were not obtained (p>0.05). In contrast, nociceptive behavioral response was significantly increased in rats submitted to both of experimental procedures (p<0.01). These findings suggest that only combination of occlusal interference and chronic stress influence masseter muscle pain.

Recent studies have indicated an increasing incidence of melanoma worldwide. Although UV signature mutations are found rarely in melanoma cells, there is some evidence that intense intermittent exposure to sunlight can induce melanocyte tumorigenesis, and this is also observed after UV irradiation in some animals. The purpose of this paper is to review some of the most important mechanisms involved in the pathogenesis of this tumor. Genetic studies showed the familiar melanoma is linked to the mutation or deletion of the suppressor gene CDKN2A, and perhaps to CDK4. Studies showed that BRAF mutation is frequent in primary and metastatic melanoma cells but also in naevocytic nevi. This mutation activates the RAF/MEK pathway. Exposure to UV radiation induces immunosuppression. Recent investigations showed that chemokines, angiogenesis, metalloproteinases can play a role in the mechanism of metastasis. In spite of these advances the initiating events are still not completely understood. In conclusion, the pathogenesis of melanoma is very complex because numerous genetic and epigenetic factors are implicated in its development and progression, but some of the showed mechanisms can be targets for new therapies.