| Background:Severe occlusal attrition(SOA) is a common disease in prosthetics, especially in the elderly, which will lead to decreased occlusal vertical distance(OVD), displaced condylar and ached muscle, even temporomandibular joint disorders. The effective therapy for SOA is occlusal reconstruction. In traditional treatment concept, it is suggested that OVD should be increased gradually and slowly when OVD need to be increased more than 4mm. At this time, doctors should increase the OVD by 2-3mm one time in order to avoid discomfort, and then restore the normal OVD. Our research team have used one-visit occlusal reconstruction to treat some SOA patients whose OVD lost more than 4mm, and they were quite satisfied with the curative effect. Furthermore, we didn’t find obvious discomfort in their masticatory muscles and temporomandibular joints(TMJs) during the follow-up. To investigate the clinical feasibility of one-visit occlusal reconstruction, we have established the rat model of one-visit occlusal reconstruction successfully. The previous studies showed that reversible injury appeared in masticatory muscles and TMJs after one-visit reconstruction. However, what happened to the injury-sensitive and pain-sensitive proteins in the masseter injury process remains unclear. Objective:In the present study, based on one-visit reconstruction rat model, several molecular biological methods were employed to analyze the morphological changes, the expression of injury-sensitive and pain-sensitive proteins in masseter muscle at different stage after one-visit reconstruction, to provide experimental and theoretical evidence for the treatment for SOA by one-visit occlusal reconstruction. Methods:1. With the help of operating microscope, the crown height of bilateral upper posterior teeth in adult SD rats were decreased progressively to establish the animal model of SOA. Then occlusal splints were made and adhered to the surface of the decreased teeth. SD rats were set up into control group, sham group and one-visit occlusal rehabilitation group, and then divided into four subgroups, including 3d, 7d, 14 d and 28 d respectively.2. The microstructure and ultrastructure of the masseter muscle induced by one-visit occlusal rehabilitation were observed with the help of HE stain, light microscopy and electron microscope.3. The level of desmin and s Tn I expression in masseter muscle induced by one-visit reconstruction was dectected by western blot.4. The serum level of creatine kinase(CK) and lactate dehydrogenase(LDH) was detected by automatic biochemical analyzer.5. The expression of SP in masseter muscle was detected by immunohistochemical technique. Results:1. No obvious abnormal microstructure and ultrastructure of masseter muscle was found in control group and sham group. As for the microstructure of masseter muscle in one-visit occlusal reconstruction group, it was almost normal in 3d subgroup. A few inflammatory cells between muscle fibers appeared in 7d subgroup, and then the number of inflammatory cells began to increased, with the most inflammatory cells in 14 d subgroup. After that, the number of inflammatory cells decreased gradually to normal level in 28 d subgroup. As for the ultrastructure of masseter muscle in one-visit occlusal reconstruction group, mitochondrion deformation and expansion were found in 3d subgroup. Obvious mitochondrial swollen changes with fuzzy cristae or cristae loss were found in 7d subgroup. However, only slight mitochondrial swollen changes were found in 14 d subgroup, and no obvious changes in 28 d subgroup.2. Compared to control group and sham group, the expression of desmin and s Tn I protein in the masseter muscle decreased significantly in 3d subgroup after one-visit occlusal rehabilitation(P < 0.05), and decreased to the lowest level in 7d subgroup(P < 0.01). Then the protein expression began to increase gradually, with the normal level in 28 d subgroup(P > 0.05).3. Compared to control group and sham group, the serum level of CK and LDH in one-visit occlusal rehabilitation group showed no significant difference(P > 0.05).4. There were no expression of SP in control group and sham group. There was few expression of SP in the masseter muscle in 3d subgroup, and a lot of expression of SP was found not only in the masseter muscle fibres but also between the muscle fibers in 7d subgroup. Then the expression of SP decreased and only be found in the nerve fibers in 14 d subgroup. Almost no SP expression was found in 28 d subgroup. Conclusion:1. Induced by one-visit occlusal rehabilitation, injury changes could be found in the microstructure and ultrastructure of the masseter muscle, but as the time going, masseter muscle would gradually recover to the normal status.2. Induced by one-visit occlusal rehabilitation, the expression of desmin and s Tn I in masseter muscle decreased firstly, and then increased gradually, finally recovered the normal level.3. No significant changes were found in the serum level of creatine kinase(CK) and lactate dehydrogenase(LDH) after one-visit occlusal rehabilitation.4. Induced by one-visit occlusal rehabilitation, the expression of SP in masseter muscle increased firstly, and then decreased gradully, with the normal level in the end. |
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