| Objective:The first, by an epidemiological investigation of TMD in the Urumqi adolescent, to achieve a comprehensive analysis of TMD signs and symptoms and relationship associated with the mental problems, the second, by establishing rat model of psychological stress, to explore the function and pathological changes of masseter muscle tissue and temporomandibular joint tissue, and by immunohistochemical method, to analyze the expression of some cytokines and their effect on TMD, then by testing COMT gene with the fluorescent quantitative PCR techonology, to discuss preliminarily the effect of psychological stress on TMD and possibly infuencing mechanisms. Methods: part1:Epidemiology:1408students in Urumqi city, between7th to9th grades, age from12～15, were investigated using random cluster sampling survey, including mental status questionnaire and temporomandibular joint symptoms and signs check, and the incidence of TMD and the relationship associated with mental stress were analyzed. Part2:①48male wister’rats, were randomly divided into4groups with12rats in each group, of which psychological stress group was divided into3-week-group,6-week-group, and a recovery group of6weeks, while another group is control group. Under the same feeding conditions, stressed groups were stimulated with electric shock in feet, temperature conditioning of climate box, food temptations, and body braking of iron drum, and four ways were chosed alternately and randomly. During the different time of3th week,6th week, and recovered6week, measured the consume quantity of water and food, weight change and rats’ scores in opened field experiment, and then killed the rats and got anatomically complete masseter muscle and temporomandibular joint tissue for reserve.②The temporomandibular joint were fixed, sliced, and observed under light microscope.③The expressions of MMP-3, TIMP-3, VEGF, and TGF-β1were observed and analyzed in condylar cartilage cells of rats’temporomandibular joint by immunohistochemical technology. Part3:①The serum creatine kinase (CK), C reactive protein (CRP), and lactate dehydrogenase (LDH) in each group were tested and analyzed under the low-temperature centrifuge and the automatic biochemical analyzer.②COMT fluorescence quantitative PCR and gel electrophoresis were done with the masseter muscle reserved in refrigerator of-80℃. Results:part1:Of1408junior high school students, people with more than one TMD signs was156(11.8%), and people with more than1TMD symptoms was298(21.16%). There was a close relation with the three chief TMD signs (trismus, snapping and murmur, muscle and joint pain), as well as abnormal oral function (clenching and bruxism) and mental state, P<0.001.part2:①According to the the average weight, average feeding intake of water and the scores of field open experiment behavioral changes of rats, the three stressed groups were different from the control group, with a statistics significance. The score of6th week group stressed was significantly higher than that of the3th week group, and the difference was statistically significant.②In the3rd week and the6th week group stressed psychologically, the collagen fibrils on the surface of condylar arranged in disorder, with local roughness, and the number of cartilage cell layers decreased in the area of proliferation and hyaline cartilage to less than3-5layers. The TMJ showed cartilage fracture, bone trabecular derangement, and squeezed disc, of which the6th group changed more significantly than the3th group (P<0.05), while the recorvered group was similar to the3th group with relieved synovial edema.③Immunohistochemistry showed various cytokines in joint tissues were visible expression. The expression rate of MMP-3of stressed6th group was significantly higher than that of control group (P<0.01), and the3th group was also higher than the control group (P<0.05), but between the other groups hadn’t significant difference; the expression of TIMP-3of the recovered group was significantly higher than the control group, P<0.05; the expression of VEGF in the recovered group was significantly greater than that in the3th stressed group and control group, P<0.05; TGF-β1of the6th group expressed more significantly than in the control group, P<0.05. part3:①Values of CK and LDH in the3rd,6th week group stressed psychologically and the recorvered group were significantly higher than those in control group and there was statistical significance (P<0.05). CRP of the recovered group was significantly higher than other groups (P<0.05), and the others showed no significant differences (P>0.05).②The gene fluorescence quantitative PCR of COMT showed statistical significance in four groups,Hc=8.355, P=0.039, the COMT expression levels of rat masseter muscle followed by6th week,3th week, the recovered group and the control group from low to high. Conclusion:Part1:The prevalence of TMD in children and adolescents is relatively high, the symptoms and signs were related to some psychological factors, and this situation should be concerned. Part2:the rats’ behavior can be changed under longtime stimulation by foot electric shock, body brake, climate conditioner, and food temptation, and the rats can display extremely nervous and fear. Due to the comprehensive valuation of body weight, food and water intake, and open field testing, it can be concluded that the the stressed animal models was achieved, or the rats can be considered in such a state of psychological stress. Temporomandibular joint structure showed some pathological changes, especially in cartilage layer of mandibular condyle, with structure disorders, decreased number of cartilage layer, fracture, and these pathological changes was proportional to the stimulation time. After removal of stress stimulation, the lesions can be recovered or restored partially. In severe case of pathological changes, the positive rate of MMP-3was high and the over expression could be related with the damage of TMJ structure tissue. More expression of TIMP-1shows that it plays an important role in the recovery group. The expression of VEGF in articular cartilage illustrates the angiogenesis phenomena after the removal of stimulation. The expression of TGF-β1in chondrocyte is proportional to the degree of tissue lesion, and it is possible that more bone resorption and less osteogenesis happens under the psychological stress, moreover among various factors may have interaction. Part3: Under the situation of psychological stress, CK and LDH in rats’ masseter muscle increased and muscle activity changed significantly, morever, proving that there are some relative muscle pathological changes such as inflammatory changes and possible energy metabolism disorder. The COMT of masseter muscle will decrease under longtime psychological stress, and CA secrete more so that the masseter shows spasm, over contraction, and dysfunction, due to the muscle blood circulation disorders and ischemia. |
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