| Temporomandibular disorders(TMD) occur frequently in dental clinic. Its main pathological change is degeneration of the condylar cartilage, which has close relationship with abnormal loading experienced by associated tissure. As a weight-loaded joint, the main load of temporomandibular joint(TMJ) is due to contraction of masticatory muscles. To investigate the relationship between oclusion and the change of TMJ, the animal models of gradually-induced-occlusal-disorder in monkey, rabbit and rat were established by our research team since 2000. It has been confirmed that occlusal disorder could lead to abnormal remodeling activities of condylar cartilage. On the basis of previous studies, to investigate the expression of FGF2, FGFR1 and IL-1βin abnormal remodeling of condylar cartilage induced by gradually induced occlusal disorder, rats of different ages were chosen.Materials and method:Twenty-four young (4 weeks old) and 24 adult(8 weeks old) female SD rats were divided into experimental group and control group. For experimental group, to develop occlusion disorders, elastic rubbers were inserted between the first and second molar in the left upper side and right lower side. The first molar was moved anteriorly gradually. There will be a distance about 0.6 millimeter between the first and second molars one week later. Self-concreting plastic were put into the gap to keep the distance(lower than occlusal surface). Three rats of each group were killed 2,4,6,8 weeks after treatment. Another 3 young and 3 adult female rats were chosen as occlusal-disorder removed group. Firstly, they were treated by the same procedure as experimental group. Then the disorderd first molars were extracted to remove the occlusal disorder 6 weeks later. These 6 rats were killed 2 weeks later. The expressions of FGF2, FGFR1 and IL-1βwere detected by immunohistochemistry.Results:1. The expression of FGF2:①FGF2 was abundant in the proliferative cell layer, maturative layer and hypertrophical cell layer in the rat condylar cartilage.②In control groups, the expression of FGF2 increased from 6-week-old to 10-week-old, then decreased gradually during experiment period.③In both young and adult animals, the expression of FGF2 in experimental groups was higher than that of control groups at 2 weeks, 6 weeks and 8 weeks after treatment, lower than that of control groups. There was no significant difference between experimental and control groups at 4 weeks after treatment.2. The expression of FGFR1:①FGFR1 was abundant in the maturative layer and hypertrophic layer, but few FGFR1-positive chondrocytes were found in proliferative layer.②In control groups, the expression of FGFR1 increased from 6-week-old to 10-week-old, and then decreased and went stable.③In both young groups and adult groups, the expression of FGFR1 in experiment group was lower at 4, 6 weeks and higher at 8 weeks after treatment than that in control group, especially in young group. But no difference was found between experiment groups and control groups at 2 weeks after treatment in both groups. 3. The expression of IL-1β:①IL-1βwas abundant in the maturative layer and hypertrophic layer.②In control groups, the expression of IL-1βwas relatively stable from 6-week-old to 16-week-old, with a little increase at 10-week-old.③The expression of FGFR1 in experiment groups was higher than that in control groups at 8 weeks after treatment, while no difference was found at 2, 4, 6 weeks after treatment in both groups.4. After removing the disordered occlusion, the expression of FGF2, FGFR1 and IL-1βin young group and adult group decreased significantly. The expression was lower than experimental groups, but no difference with control groups.Conclusion:The gradually-induced-occlusion-disorder can induce the remodeling activities of condylar cartilage. In this process, the expression of FGF2, FGFR1 and IL-1βincreases significantly, which indicates that FGF2, FGFR1 and IL-1βmay play an important role in the remodeling of condylar cartilage induced by occlusal disorders.After removing the disordered occlusion, the expression of FGF2, FGFR1 and IL-1βrecover to normal level.
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